Can supervise: YES
Characterisation of Australian Opal:Characterisation of the thermophysical, mechnical and microstructural properties of Australian sedimentary and volcanic opals (as well as opal derived from international sources for comparison).Development of Advanced Blended Cements:Pitchstone fines as a pozzolanic additive for the replacement of Portland cement in both hydrothermally (autoclaved) and air cured cements.Clay brick waste as a pozzolanic additive for the replacement of Portland cement in hydrothermally (autoclaved) cured cements.Magnesia Cements - use of reactive magnesia coupled with pozzolanic additives for the replacement of Portland cement in both hydrothermally (autoclaved) cured cements.Taphonomy of Bone:Characterisation of the aging mechnism of bone in a variety of environments for forensic applications.Generic Areas of Research Interest:Application of Thermal Analysis to Materials CharacterisationNonisothermal Kinetic Analysis Using Thermal Methods
Boyd-Weetman, B & Thomas, P 2020, 'Assessment of the ground aggregate paste (GAP) test for aggregate alkali–silica reactivity screening', Journal of Thermal Analysis and Calorimetry.View/Download from: Publisher's site
© 2020, Akadémiai Kiadó, Budapest, Hungary. This paper investigates the potential of a laboratory test for the screening of aggregate reactivity to alkali–silica reaction (ASR) through phase analysis of the phases developed in ground aggregate paste (GAP) specimens subjected to accelerated ageing. GAPs were prepared using two aggregates categorised as non-reactive and potentially reactive by standard expansion test methods and were aged at 40, 60 and 80 °C in 1 M NaOH solution over periods up to 84 days. Phase development was monitored using TG, XRD and FTIR, and the reactivity was correlated with quartz and calcium hydroxide consumption. The data demonstrate that this test has the potential to be developed as a screening test, based on the correlation of phase consumption with Australian standard expansion test reactivity categorisation.
Chauviré, B & Thomas, PS 2020, 'DSC of natural opal: insights into the incorporation of crystallisable water in the opal microstructure', Journal of Thermal Analysis and Calorimetry.View/Download from: Publisher's site
© 2019, Akadémiai Kiadó, Budapest, Hungary. Low-temperature DSC on a wide range of opal-A and opal-CT samples was carried out to estimate the proportion of crystallisable water and to determine the size of water-filled cavities. A wide range of crystallisable water contents in the range 4.9 to 41.9% of the water contained in opals were observed, although the proportion of crystallisable water did not correlate with structure. Pore size and pore size distribution were estimated from the melt temperature depression and heat flow data, respectively. Opal-CT was observed to have smaller water-filled pores (radii < 2 nm) than opal-A (radii from 2.5 to 4.9 nm), suggesting that molecular water may be contained between nanograins in the microstructural units (spheres or lepispheres). A narrower pore size distribution was calculated for opal-CT, and no melting of the crystallisable water was observed where bulk water would be expected to melt, suggesting the absence of larger voids. The melting peaks for opal-A, on the other hand, transitioned into the melting of bulk water suggesting the presence of significantly larger water-filled pores, an observation consistent with the microstructure observed in SEM micrographs.
© 2020 Elsevier Ltd and Techna Group S.r.l. Opal is a hydrous silica (Si02.nH2O) formed through a dissolution-precipitation process. The formation process incorporates water into the structure as bound silanol and molecular water. As the water is distributed in a range of states, multiple methods of characterisation are required to identify each state. This study reports the results of temperature dependent FT-NIR and DSC investigation on natural opal samples of the opal-A (amorphous) and opal-CT (poorly crystalline cristobalite with tridymitic stacking faults) types. Significant differences in the melting behaviour of crystallisable water as well as differences in the spectral characteristics of the non-crystallisable molecular water are observed. These differences are ascribed to the different microstructures of the opal types.
Canola oil, refined mineral oil, and crude oil additions up to 10% of the aggregate mass in
Portland cement mortars were found to decrease the 28-day compressive strength by 71%, 75% and 50%,
respectively, and retard setting times. There was a progressive impact upon cement hydration as the oil content
increased in mortars. Only in the case of vegetable oil and refined mineral oil could strength loss be attributed
in part to cement hydration inhibition, as evidenced by reduced total evolved heat. It is likely that
microstructural effects were also a key factor in strength loss for all mortars particularly for those containing
Maynard-Casely, HE, Booth, N, Leung, AE, Stuart, BH & Thomas, PS 2019, 'Potential of neutron powder diffraction for the study of solid triacylglycerols', Food Structure, vol. 22.View/Download from: Publisher's site
© 2019 We present a high-resolution neutron powder diffraction study of the triclinic β form of tripalmitin as well as in situ crystallisation experiments, monitored with neutron diffraction, conducted over three different cooling rates. We use the results from the high-resolution study to anticipate if neutron diffraction could be beneficial in differentiating the polymorphism in triacylglycerol systems. We extend on this to present analysis of a diffraction pattern of cocoa butter, to establish the potential for neutron diffraction to study the (hydrogenous) forms of triacylglycerols used in food production.
Stuart, BH, Maynard-Casely, HE, Booth, N, Leung, AE & Thomas, PS 2019, 'Neutron diffraction of deuterated tripalmitin and the influence of shear on its crystallisation.', Chemistry and physics of lipids, vol. 221, pp. 108-113.View/Download from: Publisher's site
This neutron diffraction study of deuterated tripalmitin has provided further insight into a forensic observation of the crystallisation of lipids under high-shear conditions. To achieve this, an experimental set up was designed to enable simultaneous rheological data from a Couette cell to be recorded with neutron powder diffraction, enabling the influence of shear on the polymorph transformation on cooling to be monitored in real time. Tripalmitin was observed to directly transform from a liquid phase to a β polymorph under the influence of shear. Although the liquid to β transition was not observed to be influenced by shear rate, the degree of crystallinity, qualitatively denoted by an increase in the sharpness of the diffraction peaks, was observed at higher shear rates. Evidence is also presented that the rate of cooling influences the ordering in the β-polymorph produced in zero shear conditions.
Stuart, BH, Thomas, PS, Barrett, M & Head, K 2019, 'Modelling clay materials used in artworks: an infrared spectroscopic investigation', Heritage Science, vol. 7, no. 1.View/Download from: Publisher's site
Sullivan, C, Thomas, P & Stuart, B 2019, 'An atomic force microscopy investigation of plastic wrapping materials of forensic relevance buried in soil environments', Australian Journal of Forensic Sciences, vol. 51, no. 5, pp. 596-605.View/Download from: Publisher's site
© 2018 Australian Academy of Forensic Sciences Plastics are one means of disposal of items or remains associated with criminal activity. The surface characteristics of plastic wrapping materials of forensic interest in soil environments have been investigated to determine the environmental factors that have the greatest influence on the degradation process of such polymers. Polyethylene bags and poly(vinyl chloride) sheeting were buried in model environments encompassing different soil types, moisture content, pH and temperature. Atomic force microscopy was used to monitor the changes to the polymer surface at a nanometre level. Over a two-year burial period, the degradation of polyethylene was found to be enhanced by an increased moisture content and an elevated soil pH. The plasticizer content of poly(vinyl chloride) was affected by burial and was observed to leach from the plastic in all environments continually over the burial period. A moist environment was shown to have a more pronounced effect on the removal of plasticizer. A measurement of the surface roughness of plastics using atomic force microscopy has been shown to be sensitive to the burial environment and demonstrates the potential of this technique to measure relatively subtle changes to burial items exposed to different environments.
Thomas, P, Aldrige, L & Smallwood, A 2019, 'Water in opal – what can it tell us?', InColor Magazine, no. 41, pp. 62-69.
Opal is a hydrous silica composed of predominantly silicon dioxide and water. The chemical composition of opal is normally described by the general formula SiO2.nH2O. The formula indicates that opal contains water and the value of 'n' is variable so the water content is variable and is known to range widely. Such a simple formula hides much of the important characteristics of how water is contained in opal and the variability in the water content and states of water is intricately involved in the formation of opal and may influence properties of the opal as a gemstone. The understanding of the states of water in opal is therefore of importance. The way in which the water is contained provides clues to the mechanisms of formation of opal. The water contained may also be used as a probe to help elucidate the complex microstructure beyond the sphere array structure in which precious opal, in particular, is described. This article will outline the types of water present in opal that displays play-of colour (POC) and how these types have been determined using chemical and physical laboratory characterisation techniques.
Pace, B, Munroe, P, Marjo, CE, Thomas, P, Gong, B, Shepherd, J, Buss, W & Joseph, S 2018, 'The mechanisms and consequences of inorganic reactions during the production of ferrous sulphate enriched bamboo biochars', Journal of Analytical and Applied Pyrolysis, vol. 131, pp. 101-112.View/Download from: Publisher's site
© 2018 Elsevier B.V. Magnetic biochars are implicated in graphene micro-crystallite formation, soil redox processes and highly adsorbent chars. This study investigates the mechanisms of bamboo charring – when impregnated with FeSO4·7H2O – at 250, 350, 450 and 550 °C, using thermal and static techniques. Impregnation resulted in the oxidation of Fe2+ to mixed Fe3+/Fe2+ (magnetite) oxide forms during pyrolysis. A reaction sequence was proposed in which Fe-sulphates were incorporated with an ammonia catalyst. Sulphur became ubiquitous in both inorganic and organic forms, and additional minerals also formed. Stable aromatics and separation of holo-cellulosic and degraded lignin volatilisation phases were catalysed, and carboxylation was inhibited. Concentrations of C fluctuated more substantially, before stabilising at high HTTs. Pyrolysis temperatures of 450 °C and above appear to maximise stable C concentrations.These observations indicated that this treatment may yield agriculturally engineered chars with enhanced redox potential, more neutral pH, and a range of nutrients.
Tapas, M, Brenner, J, Vessalas, K, Thomas, P & Sirivivatnanon, V 2018, 'Effect of Limestone Content in Cement on Alkali-Silica Reaction Using Accelerated Mortar Bar Test', Concrete in Australia, vol. 44, no. 2, pp. 41-47.
This paper reports the effect of interground limestone content on Alkali Silica Reaction (ASR) in binder systems with and without supplementary cementitious materials (SCMs) using commercial Portland cement (Type GP) with no limestone addition and a masonry cement with 17% limestone. The results show that increasing cement limestone content up to 17% has no adverse effect on expansion of mortar bars containing reactive greywacke aggregate tested using Australian Standard AS 1141.60.1. The high limestone content of 17% also appears to stabilise the Accelerated Mortar Bar Test (AMBT) expansion after 14 days of immersion in 1M NaOH 80 oC. This is possibly because of the formation of monocarboaluminate as detected by X-Ray Diffraction (XRD), resulting from the reaction of limestone with the aluminate phases in the cement, which may lead to reduced porosity in the mortar as well as the reduced amount of portlandite in the hydrated masonry cement as confirmed by Thermogravimetric Analysis (TGA). Moreover, it was found that the limestone content had no detrimental effect on the efficacy of SCMs to suppress ASR as shown in the expansion of the accelerated mortar bar tests.
Wu, W-H, Thomas, P, Hume, P & Jin, J 2018, 'Effective Conversion of Amide to Carboxylic Acid on Polymers of Intrinsic Microporosity (PIM-1) with Nitrous Acid.', Membranes, vol. 8, no. 2.View/Download from: Publisher's site
Carboxylate-functionalised polymers of intrinsic microporosity (C-PIMs) are highly desirable materials for membrane separation applications. The recently reported method to afford C-PIMs was via an extensive base hydrolysis process requiring 360 h. Herein, a novel and effective method to convert PIM-CONH₂ to C-PIM using nitrous acid was studied. The chemical structure of C-PIM was characterised by ¹H NMR, 13C NMR, FTIR, elemental analysis, UV-Vis, TGA and TGA-MS. Complete conversion from amide to carboxylic acid groups was confirmed. Decarboxylation of C-PIM was also successfully studied by TGA-MS for the first time, with a loss of m/z 44 amu (CO₂) observed at the first degradation stage. TGA also revealed decreased thermal stability of C-PIM relative to PIM-CONH₂ under both N₂ and air atmosphere. Gel permeation chromatography (GPC) analysis showed continuous molecular weight degradation of C-PIM with extended reaction time. Aromatic nitration was also observed as a side reaction in some cases.
Booth, N, Davidson, G, Imperia, P, Lee, S, Stuart, B, Thomas, P, Komatsu, K, Yamane, R, Prescott, SW, Maynard-Casely, HE, Nelson, A & Rule, KC 2017, 'Three impossible things before lunch - The task of a sample environment specialist', Journal of Neutron Research, vol. 19, no. 1-2, pp. 49-56.View/Download from: Publisher's site
© 2017 - IOS Press and the authors. All rights reserved. In the course of their day, sample environment professionals can be confronted by numerous technical challenges applicable to a range of scientific questions. This paper presents three successful outcomes from user-posed sample environment challenges for in situ neutron scattering experiments undertaken at the Australian Centre for Neutron Scattering (formerly the Bragg Institute). The sample environments presented here have nothing in common other than their novelty. They may not be the best solution but have been constrained by time, resources and ability. The questions the users posed were: Can we mount a cylinder in cylinder (CIC) rheometer, more regularly used on a small angle scattering instrument, on a diffraction instrument and obtain usable data? Can we supply high-voltage (up to 10 kV) across a sample within the Paris-Edinburgh press while mounted on a powder diffraction instrument? And finally can a Lakeshore 340 and an in-house built liquid conductivity cell do the job of a commercial liquid conductivity meter? This paper presents the engineering and equipment solutions that were used to answer these questions, and in each case the scientific users left with useful, intriguing and, hopefully, publishable data.
Chua, L, Head, K, Thomas, P & Stuart, B 2017, 'FTIR and Raman microscopy of organic binders and extraneous organic materials on painted ceremonial objects from the Highlands of Papua New Guinea', Microchemical Journal, vol. 134, pp. 246-256.View/Download from: Publisher's site
© 2017 Elsevier B.V. This paper presents a challenging case where organic materials in micro-sized paint samples extracted from mid-20th century ceremonial objects of the Papua New Guinea (PNG) Highlands are characterized using FTIR microscopy, with the aid of solvent extraction and pre-treatment with hydrofluoric acid (HF) targeted for micro-sized samples, as well as Raman microscopy and SEM-EDS. An eclectic range of binder classes including plant-based organic matter, animal fat, wax, natural and synthetic resin, were identified on several ceremonial objects based on spectral signatures. The tree resins detected (tigaso oil and kilt tree resin) are specific to the natural flora from the PNG Highlands. Tannin-rich charred wood forming the base substrate of different ceremonial objects was also identified. In addition, degradation products from metal soaps from both synthetic and biological sources were identified.
Stuart, BH & Thomas, PS 2017, 'Pigment characterisation in Australian rock art: A review of modern instrumental methods of analysis', Heritage Science, vol. 5, no. 1, pp. 1-6.View/Download from: Publisher's site
© 2017 The Author(s). The many thousands of Aboriginal rock art sites extending across Australia represent an important cultural record. The styles and materials used to produce such art are of great interest to archaeologists and those concerned with the protection of these significant works. Through an analysis of the mineral pigments utilised in Australian rock art, insight into the age of paintings and practices employed by artists can be gained. In recent years, there has been an expansion in the use of modern analytical techniques to investigate rock art pigments and this paper provides a review of the application of such techniques to Australian sites. The types of archaeological information that may be extracted via chemical analysis of specimens collected from or at rock art sites across the country are discussed. A review of the applicability of the techniques used for elemental analysis and structural characterisation of rock art pigments is provided and how future technological developments will influence the discipline is investigated.
Chua, L, Head, K, Thomas, P & Stuart, B 2016, 'Micro-characterisation of the colour palette of ceremonial objects from the Papua New Guinea Highlands: Transition from natural to synthetic pigments', MICROCHEMICAL JOURNAL, vol. 124, pp. 547-558.View/Download from: Publisher's site
Chua, L, Maynard-Casely, HE, Thomas, PS, Head, K & Stuart, BH 2016, 'Characterisation of blue pigments from ceremonial objects of the Southern Highlands in Papua New Guinea using vibrational spectroscopy and X-ray diffraction', VIBRATIONAL SPECTROSCOPY, vol. 85, pp. 43-47.View/Download from: Publisher's site
Hunt, A, Thomas, P, James, D, David, B, Geneste, J-M, Delannoy, J-J & Stuart, B 2016, 'The characterisation of pigments used in X-ray rock art at Dalakngalarr 1, central-western Arnhem Land', MICROCHEMICAL JOURNAL, vol. 126, pp. 524-529.View/Download from: Publisher's site
Thomas, PS, Heide, K & Földvari, M 2015, 'Water and hydrogen release from perlites and opal: A study with a directly coupled evolved gas analyzing system (DEGAS)', Journal of Thermal Analysis and Calorimetry, vol. 120, no. 1, pp. 95-101.View/Download from: Publisher's site
© 2014 Akadémiai Kiadó, Budapest, Hungary The dehydration of two specimens of perlite from Pálháza (Hungary) and from Borovitza (Bulgaria) along with a specimen of Australian precious opal has been investigated by temperature controlled high-vacuum degassing experiments (DEGAS). Dehydration results in the loss of water over a wide range of temperatures due to the presence of both molecular and bound (silanol, Si–OH) water. A surprising observation is that hydrogen (H2) is also released. The hydrogen is observed to be released from both perlites and opal and both by diffusional processes and through the sudden explosive, bursting of inclusions which produce sharp spikes in the MS data. The origin of the hydrogen cannot be explained by a simple statistical distribution of the silanol species in the vitreous matrix; rather, it is more likely to be associated with an inverse-micellar decomposition of silanol species. Alternate sources of hydrogen such as meteoric waters or specific genetic origins based on the perlite or opal location and formation are discounted as the hydrogen release is found to be independent of CO2 and SO2 evolution.
Fukumoto, T, Thomas, P, Simon, P, Dubaj, T & Stuart, BH 2014, 'Estimation of the curing rate of acrylamide used as a consolidant in heritage sandstone conservation', Journal of Thermal Analysis and Calorimetry, vol. 116, pp. 619-624.View/Download from: Publisher's site
Simon, P, Thomas, P, Dubaj, T, Cibulkova, Z, Peller, A & Veverka, M 2014, 'The mathematical incorrectness of the integral isoconversional methods in case of variable activation energy and the consequences', JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, vol. 115, no. 1, pp. 853-859.View/Download from: Publisher's site
Liu, B, Ray, AS & Thomas, P 2013, 'Investigation of autoclaved cement systems with reactive MgO and Al2O3-SiO2 rich fired clay brick', Advances In Cement Research, vol. 25, no. 5, pp. 281-287.View/Download from: Publisher's site
Portland cement (PC) is one of the world's most important building materials, as it is a fundamental component of concrete. However, the manufacture of PC is highly energy intensive and leads to the emission of carbon dioxide (CO2). One promising control
Thomas, P, Guerbois, JL & Smallwood, AG 2013, 'Low temperature DSC characterisation of water in opal', Journal of Thermal Analysis and Calorimetry, vol. 113, no. 3, pp. 1255-1260.View/Download from: Publisher's site
A low temperature (-60 to +105 A degrees C) DSC characterisation of opal was carried out to determine the proportion of crystallisable water and to estimate the cavity size in which the crystallisable water is contained. Circa 10 % of the molecular water
Angus, KL, Thomas, P & Guerbois, JL 2012, 'Synthesis and characterisation of cobaltite and ferrite spinels using thermogravimetric analysis and X-ray crystallography', Journal of Thermal Analysis and Calorimetry, vol. 108, pp. 449-452.View/Download from: Publisher's site
The synthesis for a series of ferrite ((MFe2O4)-Fe-II) and cobaltite ((MCo2O4)-Co-II) spinels was investigated where M-II is Mg, Co, Ni, Cu or Zn. The ferrites were prepared at a calcination temperature of 800 A degrees C; the cobaltites at 500 A degrees
Fukumoto, T, Thomas, PS, Stuart, BH, Simon, P, Adam, G, Shimmon, R & Guerbois, J-P 2012, 'Estimation of the storage life of dimethylol urea using non-isothermal accelerated testing', Journal of Thermal Analysis and Calorimetry, vol. 108, no. 2, pp. 439-443.View/Download from: Publisher's site
Hamedanimojarrad, P, Adam, G, Ray, AS, Thomas, P & Vessalas, K 2012, 'Development of shrinkage resistant microfibre-reinforced cement-based composites', Central European Journal of Engineering, vol. 2, no. 2, pp. 289-295.
Different shrinkage types may cause serious durability dilemma on restrained concrete parts due to crack formation and propagation. Several classes of fibres are used by concrete industry in order to reduce crack size and crack number. In previous studies, most of these fibre types were found to be effective in reducing the number and sizes of the cracks, but not in shrinkage strain reduction. This study deals with the influence of a newly introduced type of polyethylene fibre on drying shrinkage reduction. The novel fibre is a polyethylene microfibre in a new geometry, which is proved to reduce the amount of total shrinkage in mortars. This special hydrophobic polyethylene microfibre also reduces moisture loss of mortar samples. The experimental results on short and long-term drying shrinkage as well as on several other properties are reported. The hydrophobic polyethylene microfibre showed promising improvement in shrinkage reduction even at very low concentrations (0.1% of cement weight).
Hamedanimojarrad, P, Galea, N, Ray, AS, Adam, G, Vessalas, K & Thomas, P 2012, 'New mechanisms for drying shrinkage compensation in cementitious materials', Concrete in Australia, vol. 38, no. 3, pp. 33-38.
There are several materials and methods which have been designed and used for reduction or compensation of drying shrinkage deformations in cementitious materials, in both industry and research . Typical strategies currently used in industry for overcoming drying shrinkage include introduction of expansive agents; use of shrinkage reducing admixtures (SRA) and fibres as components of mixtures; cement modification; and, taking advantage of internal curing (Kovler & Zhutovsky, 2006).
Howes, JM, Stuart, BH, Thomas, P, Raja, S & O'Brien, RC 2012, 'An investigation of model forensic bone in soil environments studied using infrared spectroscopy', Journal of Forensic Sciences, vol. 57, no. 5, pp. 1161-1167.View/Download from: Publisher's site
Infrared spectroscopy has been used to examine changes to bone chemistry as a result of soil burial. Pig carcasses were buried as part of a controlled field study, and pig bone was used in soil environments established in the laboratory. The variables of species type, bone pretreatment, soil type and pH, moisture content, temperature, and burial time were investigated. The crystallinity index (CI) and the organic and carbonate contents of the bones were monitored. The data revealed decreasing trends in the organic and carbonate contents and an increase in the CI of the bone with burial time. An acidic soil environment and soil type are the factors that have the most influence on bone chemistry as a result of burial. The study demonstrates the potential of infrared spectroscopy as a straightforward method of monitoring the changes associated with aging of bones in a variety of soil environments.
Yang, L, Thomas, P & Stuart, BH 2012, 'Discrimination of thermally treated low density polyethylenes using DSC and principal component analysis', Journal of Thermal Analysis and Calorimetry, vol. 108, no. 2, pp. 445-448.View/Download from: Publisher's site
The potential for differential scanning calorimetry (DSC) as a tool for the discrimination of forensic polymer specimens is investigated for a series of commercial low density polyethylene (LDPE) samples. Variation in the melting temperatures of 'as received' samples was found to be too small for its use in sample discrimination. The melting behaviour of thermally treated samples, quenched from the melt in liquid nitrogen followed by annealing at temperatures below the melting temperature, showed promise in discrimination potential. The application of principal component analysis to aid discrimination demonstrated the necessity in using a controlled thermal history to aid the discrimination process. The clustering of the LDPEs based on the factors selected demonstrated the potential of DSC for the discrimination of forensic LDPE samples.
Aldridge, LP, Vessalas, K, Fernando, K, Costa, MD, Thomas, P & Ray, AS 2011, 'Comparison of durability measures of concrete as a function of cure times', Concrete in Australia, vol. 36, no. 4, pp. 42-47.
This work forms part of a project for evaluating techniques of estimating concrete durability to improve service life. Here compressive strength, chloride diffusivity, void volume, and sorptivity from water cured concretes were measured at seven, 28 and 56 days to evaluate the concrete durability as a function of curing. It was concluded that while void volume and sorptivity were useful as quality control measures they did not reflect the increase in durability found when concrete was cured. This was in contrast to the chloride diffusivity and compressive strength results which showed marked differences during the curing of the concrete. For this study four concrete mixes were prepared using identical compositions of water, sand, and aggregates and having the same amount of cementitious materials with four different compositions: (1) Ordinary Portland Cement (OPC) (2) OPC with 20% replacement of a commercial fly ash (3) OPC with 40% replacement of the same fly ash, and (4) OPC with 20% replacement by pitchstone fines. Pitchstone fines are a waste product made during the production of expandable perlite aggregate which previous work has shown to act as a supplementary cementitious material.
Ip, K, Stuart, BH, Ray, AS & Thomas, P 2011, 'ESEM-EDS Investigation of the Weathering of a Heritage Sydney Sandstone', Microscopy & Microanalysis, vol. 17, no. 2, pp. 292-295.View/Download from: Publisher's site
The degradation of Sydney sandstone used to build the heritage St Mary's Cathedral in Sydney, Australia, has been investigated using environmental scanning electron microscopy combined with energy dispersive X-ray spectroscopy. This technique provided the structural details of the cementing clay and an elemental characterization the sandstone. The observed differences in the elemental composition of the unweathered and weathered sandstones were associated with changes to the clay microstructure upon weathering. The results support the substitution theory that Fe3+ replaces Al3+ in the kaolinite clay component upon weathering. An examination of the impurities present prior to a nonstructural iron removal treatment revealed the presence of minerals that may provide a source of the elements responsible for the substitution process.
Ip, K, Stuart, BH, Thomas, P & Ray, A 2011, 'Characterisation of poly(vinyl alcohol)-montmorillonite composites with higher clay compositions', Polymer Testing, vol. 30, no. 7, pp. 732-736.View/Download from: Publisher's site
Polymer composites comprised of poly(vinyl alcohol) and montmorillonite with higher clay loadings have been prepared and characterised. The extent of intercalation in the composites was examined over a range of compositions using scanning electron microscopy energy dispersive spectroscopy and x-ray diffraction. The incorporation of an acidification step followed by washing the clay results in a homogenous polymer-clay film. The source of montmorillonite was found to have an effect on the morphology of the clay in the resulting composite. Montmorillonite was obtained from two sources and different clay structures within the polymer clay composites were identified in each case, indicating that the choice of clay is an important consideration when producing poly(vinyl alcohol) montmorillonite composites with higher clay content.
Thomas, P, Stuart, BH, McGowan, NM, Guerbois, JL, Berkahn, MB & Daniel, V 2011, 'A study of ochres from an Australian aboriginal bark painting using thermal methods', Journal Of Thermal Analysis And Calorimetry, vol. 104, no. 2, pp. 507-513.View/Download from: Publisher's site
The potential of thermogravimetric analysis (TG) as a tool for the characterisation of ochre paint used in indigenous Australian bark paintings has been investigated. TG has been combined with differential scanning calorimetry (DSC) and mass spectrometry
Hakimi, M, Feizi, N, Hassani, H, Vahedi, H & Thomas, P 2010, 'Regeneration Of Aromatic Carbonyl Compounds From The Corresponding Oximes Using Tetrapyridine Silver(Ii) Peroxydisulfate In Acetonitrile And Aqueous Media', Synthetic Communications, vol. 40, no. 5, pp. 725-731.View/Download from: Publisher's site
The results of the recovery of both aldehyde and ketone carbonyl functionalities from the
oxime derivatives in aromatic carbonyl compounds using tetrapyridine silver(II) peroxydisulfate
[Ag(py)4S2O8] as a stable, mild, and efficient oxidizing agent is reported. Yields in
excess of 85% were achieved at room temperature in both acetonitrile and aqueous media,
making the method versatile and suitable for a wide range of aromatic carbonyl oximes.
Raja, S, Thomas, P & Stuart, BH 2010, 'A study of storage conditions and treatments for forensic bone specimens using thermogravimetric analysis', Journal Of Thermal Analysis And Calorimetry, vol. 99, no. 3, pp. 869-872.View/Download from: Publisher's site
Bone provides an important source of forensic evidence. The storage conditions of bone have been recognised as a factor in maintaining the integrity of such evidence. Thermogravimetric analysis (TG) has been employed to examine the effects of storage environments and preparation methods on the structural properties of pig bones. A comparison of oven and freeze drying has been made to study the effect of storage conditions. A comparison has also been made of ground bone specimens with cut specimens. Freeze-dried hand ground specimens provided the most consistent results and, thus, this is the recommended method of preparation of bone specimens for TG analysis.
Thomas, P, Sestak, J, Heide, K, Fueglein, E & Simon, P 2010, 'Thermal properties of Australian sedimentary opals and Czech moldavites', Journal Of Thermal Analysis And Calorimetry, vol. 99, no. 3, pp. 861-867.View/Download from: Publisher's site
The thermal properties are presented for a precious opal sourced from Coober Pedy, South Australia and a moldavite from Bohemia, Czech Republic whose origins differ significantly as opal is derived from the slow isothermal diagenesis of silica, while the tektites are specimens of vitreous silica formed from the terrestrial impact of asteroids. The differences between the two glassy silicates are presented through measurement of the TG-DSC, TMA and high-vacuum-hot-extraction DEGAS analysis.
White, RJ, Thomas, P, Phillips, M, Moran, K & Wuhrer, R 2010, 'X-Ray Mapping And Scatter Diagram Analysis Of The Discoloring Products Resulting From The Interaction Of Artist'S Pigments', Microscopy & Microanalysis, vol. 16, no. 5, pp. 594-598.View/Download from: Publisher's site
The discoloring interaction between the artist's pigments cadmium yellow and the copper-containing malachite, an interaction that is conjectured to cause black spotting in oil paintings of the 19th and early 20th centuries, was examined using X-ray mappi
Connan, H, Ray, AS & Thomas, P 2009, 'Comparative Study of Finely Ground Fired Clay Brick and Kaolin Based Fillers in Autoclaved Calcium Silicate Based Building Products', Concrete Forum, vol. 2, no. 1, pp. 25-28.
The process of hydrothermal curing or autoclaving is particularly well suited to the utilisation of industrial by-products in the production of construction materials as it renders some of these waste materials highly reactive. Research fi ndings have demonstrated that when used in combination with Portland cement (OPC) in the industrially important CaO-Al2O3-SiO2-H2O system, fi nely ground fi red clay brick masonry, an aluminosilica rich waste, is suitable for the production of autoclaved construction materials. Th e use of kaolin clay as a fi ller in the production of these autoclaved calcium silicate based building products is well established. Th is paper presents a comparative study of fi nely ground clay brick industrial waste and kaolin clay used in combination with OPC under autoclaved conditions. Th e observed variations in compressive strength are discussed in the context of the presence of critical phases, which were characterised by microstructural and thermal analytical methods.
Raja, S, Thomas, P, Stuart, BH, Guerbois, JL & O'Brien, C 2009, 'The estimation of pig bone age for forensic application using thermogravimetric analysis', Journal Of Thermal Analysis And Calorimetry, vol. 98, no. 1, pp. 173-176.View/Download from: Publisher's site
An accurate means of determining bone age is a goal for forensic scientists. In this study, thermogravimetric analysis (TGA) has been used to examine pig bone specimens of different post-mortem age. Analysis of bone in both air and nitrogen atmospheres reveals a decrease in total mass loss as the bones age. Two mass loss steps due to the decomposition of the organic bone components were observed and show decreasing trends with age for decomposition in an air atmosphere. In a nitrogen atmosphere the decomposition was observed to be more complex and age dependence of the mass loss for each step was not identified. The TGA data, however, demonstrates the potential of the technique as a means of estimating post-mortem age of forensic bone specimens.
Smallwood, AG, Thomas, P, Ray, AS & Simon, P 2009, 'Application of a Fickian model of diffusion to the dehydration of graded specimens of a precious Australian sedimentary opal derived from Coober Pedy', Journal Of Thermal Analysis And Calorimetry, vol. 97, no. 2, pp. 685-688.View/Download from: Publisher's site
A model developed for the estimation of the diffusion coefficient based on Fickian diffusion is applied to the dehydration of a Coober Pedy white play of colour (precious) opal using thermogravimetric analysis (TG). The model was originally applied to bulk and powdered opal (opal with no bulk). In this paper the opal was graded prior to TG analysis. The diffusion coefficient was calculated and is reported up to the critical point of water.
Vessalas, K, Ray, AS, Thomas, P, Guerbois, JL, Joyce, PA & Haggman, J 2009, 'Pozzolanic reactivity of the supplementary cementitious material pitchstone fines by thermogravimetric analysis', Journal Of Thermal Analysis And Calorimetry, vol. 97, no. 1, pp. 71-76.View/Download from: Publisher's site
Thermogravimetric (TG) analysis was applied to the characterisation of the pozzolanic reaction in mortars containing the supplementary cementitious materials (SCMs) pitchstone fines (PF) and fly ash (FA) as partial replacements for Portland cement (PC). TG analysis was used to determine the proportion of calcium hydroxide (CH) present from the hydration of the PC based on the dehydroxylation of the CH present in the blended PC-SCM mortars. The consumption of CH indicated that both SCMs underwent the pozzolanic reaction and that PF was found to compare favourably in its pozzolanic reactivity of FA, the industry and globally accepted standard artificial pozzolan.
Vessalas, K, Ray, AS, Thomas, P, Sri Ravindrarajah, R, Joyce, PA & Haggman, J 2009, 'Pitchstone Fines - A New Naturally Occuring Pozzolan from North Queensland', Concrete Forum, vol. 2, no. 1, pp. 11-15.
Global warming presents an ever-challenging battle to humankind, as emissions arising from industrially produced gteenhouse gases are predicted to alter the long-term climatic patterns of earth. Harmful environmental emissions arising during the manufactute of Portland cements (C) can be effectively reduced by incorporating siliceous-aluminous based supplementary cementitious materials (SCMs), as partial cement replacements. In Australia, mined pitchstone fines (PF), derived as waste material from expandable perlire production, area viable SCM for reducing cement consumption using an eco-friendly approach. This paper reports on the results of an experimental investigation into the pozzolanic activity of PP. Up to 40% cement was replaced with PF in mortar mixes. In addition, PP was used to partially replace sand. Strength activity index (SM) values for PP were evaluated using accelerated 28-day compressive strengths for all PP substitution levels, with flows and wet densities of mortar mixes reported.
Vessalas, K, Ray, AS, Thomas, P, Sri Ravindrarajah, R, Joyce, PA & Haggman, J 2009, 'Pitchstone fines pozzolanic activity assessment as partial Portland cement (PC) replacements', Journal of Australasian Ceramic Society, vol. 44, no. 1, pp. 7-12.
Mined pitchstone fines (PF), derived as a waste by-product from expandable perlite production in Australia, are a viable, environmentally friendly aluminosilicate supplementary cementitious material (SCM) suitable for partial Portland cement (PC) replacement, thus reducing greenhouse gas emissions resulting from PC manufacture. This paper reports on the findings of pozzolanic activity exhibited at 10%, 20% and 40% replacement levels of PC, through compressive strength determinations of mortar after 1, 7 and 28 days ageing, using strength activity index (SAI) criteria. Additionally, flows and wet densities have been examined using a polycarboxylic based high-range water-reducing admixture (HRWRA) superplasticiser and fixed water content relative to cementitious material present for all PF substitution levels.
Ip, K, Stuart, BH, Ray, AS & Thomas, P 2008, 'A spectroscopic investigation of the weathering of a heritage Sydney sandstone', Spectrochimica Acta Part A-Molecular And Biomolecular Spectroscopy, vol. 71, no. 3, pp. 1032-1035.View/Download from: Publisher's site
Infrared spectroscopy has been employed in a study of the degradation of heritage Sydney sandstone used in St. Mary's Cathedral in Sydney, Australia. Spectra were used to characterise the clay components taken from weathered and unweathered sandstone blo
Ip, K, Stuart, BH, Thomas, P & Ray, AS 2008, 'Thermal characterization of the clay binder of heritage Sydney sandstones', Journal Of Thermal Analysis And Calorimetry, vol. 92, no. 1, pp. 97-100.View/Download from: Publisher's site
Thermal analysis has been employed in a study of the degradation of heritage Sydney sandstone used in St Mary's Cathedral in Sydney, Australia. TG and DSC have been used to characterise the clay components removed from weathered and unweathered sandstone. Two types of kaolin clays - kaolinite and its polymorph, dickite - have been identified. A higher amount of dickite present in the clay of weathered sandstone indicates that a kaolinite-to-dickite transformation occurs upon weathering. XRD hot stage analysis was also used to demonstrate the presence of a more thermally stable polymorph of the kaolinite.
Liu, B, Ray, AS & Thomas, P 2008, 'Physical and mechanical properties of autoclaved alumina-silica rich industrial waste cement systems incorporating reactive magnesia', Concrete Forum, vol. 1, no. 1, pp. 18-22.
The utilisation of industrial waste products as supplementary cementitious materials to produce blended Portland cement has increased worldwide in recent years. This study aims to investigate physical and mechanisal properties of the addition of clay-brick waste and reactive magnesia (MgO) as a low-emmission alternative to ordinary Portland cement (OPC) binders in autoclaved calcium silicate based building products
Onishi, A, Thomas, P, Stuart, BH, Guerbois, JL & Forbes, SL 2008, 'TG-MS analysis of the thermal decomposition of pig bone for forensic applications', Journal Of Thermal Analysis And Calorimetry, vol. 92, no. 1, pp. 87-90.View/Download from: Publisher's site
In order to investigate the potential of thermal analysis for the determination of post-mortem age, rib bone specimens were collected from the remains of a number of slaughtered pigs that were allowed to decompose in the Australian bush in a controlled site under a range of conditions for time periods ranging from 1 to 5 years. The bone specimens were cut in cross-section with the compact bone collected for analysis. TG-MS curves were collected by heating bone samples to 1100°C in an argon atmosphere. The TG-MS data showed significant differences for the pig bone specimens derived from the different environments and showed trends in peak size correlating with age. The reported data suggest that TG-MS has significant potential for the identification of origin as well as the ageing of skeletal remains in a forensic context.
Smallwood, AG, Thomas, P & Ray, AS 2008, 'Characterisation of the dehydration of Australian sedimentary and volcanic precious opal by thermal methods', Journal Of Thermal Analysis And Calorimetry, vol. 92, no. 1, pp. 91-95.View/Download from: Publisher's site
Smallwood, AG, Thomas, P & Ray, AS 2008, 'Comparative analysis of sedimentary and volcanic precious opals from Australia', Journal of Australasian Ceramic Society, vol. 44, no. 2, pp. 17-22.
Precious opal is Australia's national gemstone with Australian opal fields providing 90% of world production. The sedimentary geological environment associated with Cretaceous sediments of the Great Artesian Basin is the source of most precious opals in Australia. The deposit of precious opal at Tintenbar in northern NSW is the only kwnon commercial occurrence of precious opal in volcanic environment in Australia. Differences in silica structure of opal previously classified by x-ray diffraction (XRD) in the 1960's by Jones and Segnit identified three types of opal structure - amorphous opal-A, opal-CT with a porrly crystalline intergrowth cristobalite and tridymite and opal-C shwoing the cristibalite structure.
Thomas, P, Smallwood, AG, Ray, AS, Briscoe, BJ & Parsonage, D 2008, 'Nanoindentation hardness of banded Australian sedimentary opal', Journal of Physics D: Applied Physics, vol. 41, no. 7, pp. 1-6.View/Download from: Publisher's site
Nanoindentation hardness data in continuous stiffness mode are reported for banded potch and play of colour opals sourced from Lightning Ridge in New South Wales and Andamooka in South Australia. Despite the significant visible heterogeneities observed and the significant differences in origin and microstructures, as observed by SEM, and subtle differences in the elemental distributions between bands within specimens, little difference was observed in the mechanical properties. Specimens were found to be mechanically homogeneous and values of the hardness and moduli were found to be similar between samples. The creep behaviour of the specimens was also observed to be similar. It was concluded that the similarities in mechanical properties were due to the similarities in the silica morphology of the specimens, formed in similar geological environments, as differences in microstructure and trace element distribution were found not to significantly influence the observed bulk mechanical properties
Connan, H, Ray, AS & Thomas, P 2007, 'Autoclaved Lime-Colloidal Silica Slurries and Formation of Tobermorite', Journal of the Australian Ceramics Society, vol. 43, no. 2, pp. 150-153.
Connan, H, Ray, AS, Thomas, P & Guerbois, JL 2007, 'Effect of autoclaving temperature on calcium silicate-based building products containing clay-brick waste', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 1, pp. 115-119.View/Download from: Publisher's site
The utilisation of fired clay-brick waste is of interest in the manufacture of building products due to both socio-economic and technological reasons. Autoclaving is an established process for manufacturing calcium silicate-based building products that affords rapid strength development. Clay-brick waste represents a source of alternative silica, whcih is more reactive than conventionally used silica and also cntains alumina. This paper presents data on the effect of lowering the autoclaving temperature from commonly practised 180 to 170 degrees C on OPC-quartz blends conatining clay-brick fines as direct replacement of quartz at 4.3, 8.6 and 12.9 mass percentages. The hydration products of autoclaved OPC-quartz blends with clay-brick fines were characterised using simultaneous DTA-TG inc ombination with other methods.
Liu, B, Ray, AS & Thomas, P 2007, 'Strength development in autoclaved aluminosilicate rich industrial waste-cement systems containing reactive magnesia', Journal of the Australian Ceramics Society, vol. 43, no. 1, pp. 82-87.
Liu, B, Ray, AS, Thomas, P, Klimesch, DS & Guerbois, JL 2007, 'Mechanical properties of hydrothermally treated alumina-silica rich industrial waste cement system - effect of magnesia addition', Journal of Solid Waste Technology and Management, vol. 33, no. 2, pp. 61-66.
The utilisation of industrial waste products such as fly ash, blast furnace slag and fired clay-brick, as supplementary cementing materials to produce blended Portland cement (PC) has increased worldwide in recent years. The incentive was directed towards the utilisation of wastes and industrial by-products in order to minimise PC consumption, thus reduce CO2 emissions. This study aims to investigate the potential of magnesia (MgO) as a supplementary material in combination with alumina-silica rich fired clay brick waste fines. Compressive strength results showed adverse effects on the additions of brick waste fines and MgO. However, for blended PC with the addition of both brick waste and magnesia, an apparent synergy, indicating a minimising of strength reduction, was observed. X-ray diffraction (XRD) data revealed the presence of brucite, a hydration product of MgO, in the MgO blended PC suggesting a lack of pozzolanic activity of MgO.
Liu, B, Thomas, P, Ray, AS & Guerbois, JL 2007, 'A TG analysis of the effect of calcination conditions on the properties of reactive magnesia', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 1, pp. 145-149.View/Download from: Publisher's site
The reactivity of MgO obtained from calcination of magnesium carbonate at different temperatures has been investigated by means of hydration in a constant relative humidity environment at 40 degrees C for periods up to 24 days. Natural magnesite and AR g grade basic MgCO3 calcinated in the range of 500-1000 degrees C was characterised in terms of surface area, crystallite size, morphology, and hydration rate. It was foudn that the hydration rate is dependent on the surface area and crystallite size wwhere temperature was the main variable affecting them. The most reactive MgO was produced at the lowest calcination temperature with the highest surface area and the smallest crystallite size. The basic MgO specimens showed higher degree of hydration compared to the natural mgO specimens due to the smaller surface area and larger cyrstallite size. The low MgO content of the starting natural magnesite is also attributable to the lower reactivity. This preliminary study serves as a mean to investigate poetntial utilisation of reactive MgO asa supplementary cementitious material in eco-freindly cements.
Liu, B, Thomas, P, Ray, AS, Williams, RP & Donne, S 2007, 'DSC Characterisation Of Chemically Reduced Electrolytic Manganese Dioxide', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 1, pp. 177-180.View/Download from: Publisher's site
The thermal decomposition of electrolytic manganese dioxide (EMD), in an inert atmosphere, and the effect of chemical reduction on EMD, using 2-propanol under reflux (82 degrees C), was investigated by differential scanning calorimetry (DSC). This study
Onishi, A, Thomas, P, Stuart, BH, Guerbois, JL & Forbes, SL 2007, 'TG-MS characterisation of pig bone in an inert atmosphere', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 2, pp. 405-409.View/Download from: Publisher's site
A challenge for forensic examiners is the ageing and characterisation of bone fragments or decomposed skeletal remains. Due to the sensitivity of thermal methods to morphological states, thermal analysis has been selected as a technique which could overcome the difficulties. In this preliminary study, TG-MS was applied to the characterisation of bone fragments derived from the compact bone of pig rib specimens. TG-MS curves were collected by heating bone samples to 1000 degrees C in an argon atmosphere. under these conditions, both the organic and inorganic phases decomposed, producing a variety of organic fragments and carbon dioxide. Pyrolysis of the organic phase, which is composed predominantly of collagen, occurred resulting in the observation of ion fragments up to 110 amu. Selected fragments were monited and their observation is discussed in terms of the decomposition of both the collagen phase and the inorganic carbonated hydroxyapatite phase.
Ray, AS, Sri Ravindrarajah, R, Guerbois, JL, Thomas, P, Border, SN, Ray, H, Haggman, J & Joyce, P 2007, 'Evaluation of waste perlite fines in the production of construction materials', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 1, pp. 279-283.View/Download from: Publisher's site
The use of supplementary cementitious materials (SCM) is a well established practice worldwide in the manufacture of Portland cement (PC)-based construction materials. While utilisation of industrial by-products has been successful, the potential of mining wastes is yet yo receive adequate attention in the context of construction materials. In an expanded form perlite, which is a naturally occurring, hydrated volcanic siliceous glass, is an adeal material as a lightweight aggregate for usein a wide range of construction materials including concrete. The mining and processing of the grades of perlite required for the production of lightweight aggregate results inthe cereation of a fine grained waste wjhich currently hasno economic value. This paper reports preliminary data on the utilisation of waste perlite fines as a SCM in calcium silicate-based construction material and discusses the potential of this mining waste to reduce the environmental impact of the production of conventional cement-based consturction materials.
Smallwood, AG, Thomas, P, Ray, AS & Simon, P 2007, 'TMA And SEM Characterization Of The Thermal Dehydration Of Australian Sedimentary Opal', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 1, pp. 185-188.View/Download from: Publisher's site
The dehydration of samples of a Coober Pedy, South Australian sedimentary white opal, displaying play of colour, was investigated using TMA by heating the samples of the specimen to a range of temperatures between room temperature and 1000 at 200 degrees
Thomas, P, Simon, P, Smallwood, AG & Ray, AS 2007, 'Estimation of the diffusion coefficient of water evolved during the non-isothermal dehydration of Australian sedimentary opal', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 1, pp. 231-235.View/Download from: Publisher's site
The dehydration of an opal specimen was investigated by thermogravimetric analysis (TG) in powder and bulk forms. The change in geometry resulted in a significant difference in the temperature range in which dehydration occurred with peak temperatures in the differential TG (DTG) curve for the hand ground opal at 203 degrees Cand for the bulk opal at 340 degrees C. This difference waa attributed to time taken for diffusion of feree water in the bulk opal tothe specimen surface prior to evolution as a registered mass loss. A model was proposed to account for the diffusion of water and was used to estimate the diffusion coefficient.
White, RE, Thomas, P, Phillips, M, Wuhrer, R & Guerbois, JL 2007, 'Tg-ms Characterization Of The Reaction Products Of Cadmium Yellow And Malachite Artist's Pigments', Journal Of Thermal Analysis And Calorimetry, vol. 88, no. 1, pp. 181-184.View/Download from: Publisher's site
The deleterious interaction of some traditional sulphide artists pigments and copper ions results in the formation of black copper sulphides, in particular, covellite (CuS), and, hence, the discolouration of valuable artworks. In this paper the interacti
Connan, H, Klimesch, DS, Ray, AS & Thomas, P 2006, 'Thermal characterisation of autoclaved cement made with alumina-silica rich industrial waste', Journal Of Thermal Analysis And Calorimetry, vol. 84, no. 2, pp. 521-525.View/Download from: Publisher's site
The hydration products of hydrothermally cured OPC-quartz blends incorporating clay-brick waste were characterised using simultaneous DTA-TG, XRD and SEM. The exotherm above 800 degrees C on the DTA curve, due to the formation of beta-wollastonite (beta-
Thomas, P, Brown, LD, Ray, AS & Prince, K 2006, 'A SIMS study of the transition elemental distribution between bands in banded Australian sedimentary opal from the Lightning Ridge locality', Neues Jahrbuch Fur Mineralogie-Abhandlungen, vol. 182, no. 2, pp. 193-199.View/Download from: Publisher's site
The elemental distribution of trace elements in banded Australian sedimentary opals from the Lightning Ridge region was investigated using secondary ion mass spectrometry (SIMS). Data were acquired using both spot analysis and spatial analysis by steppin
White, RE, Phillips, M, Thomas, P & Wuhrer, R 2006, 'In-situ investigation of discolouration processes between historic oil paint pigments', Microchimica Acta, vol. 155, no. 1-2, pp. 319-322.View/Download from: Publisher's site
Discolouring interactions between paint pigments have been observed since the mid 19(th) century. The source of some of these discolourations is the production of copper sulfides from an interaction between cadmium sulfide pigments and copper containing
Connan, H, Klimesch, DS, Ray, AS & Thomas, P 2005, 'Autoclaved OPC-quartz blends incorporating clay-brick waste. Part I: factorial design effects on strength development', Advances In Cement Research, vol. 17, no. 4, pp. 133-141.View/Download from: Publisher's site
The utilisation of waste materials in the manufacturing of building products is of global interest due to technological and socio-economic benefits. For example, alumina-silica-rich industrial waste, such as fired clay brick, is available in large quanti
Many of Sydney's heritage buildings and monuments were built as a result of the first European settlement in the 1800s. These buildings not only display the richness of the Australian culture, but also capture the architectural and historical values of i
Lawry, J, Ray, AS, Klimesch, DS, Thomas, P, Guerbois, JL & Harrison, JW 2005, 'Thermal characterization of Portland cement-magnesia blends', Journal Of Thermal Analysis And Calorimetry, vol. 80, no. 3, pp. 637-641.View/Download from: Publisher's site
Due to growing environmental concerns and the need to use less energy-intensive building products, alternatives and improvements to Portland cement (PC) are being actively researched worldwide. Use of supplementary materials is now a common practice wher
Liu, B, Thomas, P, Williams, RP & Donne, S 2005, 'Thermal characterization of chemically reduced electrolytic manganese dioxide', Journal Of Thermal Analysis And Calorimetry, vol. 80, no. 3, pp. 625-629.View/Download from: Publisher's site
Samples of electrolytic manganese dioxide (EMD) were chemically reduced using 2-propanol under reflux (82 degrees C) for 1, 2, 3, 6 and 24 h intervals. XRD analysis showed that the gamma-MnO2 structure was preserved although the lattice dimensions were o
Simon, P, Cibulkova, Z & Thomas, P 2005, 'Accelerated thermooxidative ageing tests and their extrapolation to lower temperatures', Journal Of Thermal Analysis And Calorimetry, vol. 80, no. 2, pp. 381-385.View/Download from: Publisher's site
A procedure for the extrapolation of accelerated thermo-oxidative ageing tests to lower temperatures is proposed. The procedure involves a deconvolution of the global process into high- and low-temperature components where the extrapolation to low temper
Thomas, P & Simon, P 2005, 'A pseudo-isothermal kinetic analysis of the recrystallisation of nickel sulphide measured by non-isothermal DSC', Journal Of Thermal Analysis And Calorimetry, vol. 80, no. 1, pp. 77-80.View/Download from: Publisher's site
A pseudo-isothermal method for the kinetic analysis was applied to the recrystallisation of alpha to beta nickel sulphide based on the Ozawa model for non-isothermal crystallisation in the presence of pre-existing nuclei. The aim of the analysis was to d
White, RE, Thomas, P, Phillips, M & Wuhrer, R 2005, 'A DSC study of the effect of lead pigments on the drying of cold pressed linseed oil', Journal Of Thermal Analysis And Calorimetry, vol. 80, no. 1, pp. 237-239.View/Download from: Publisher's site
Cold pressed linseed oil and paints prepared using the inorganic pigments; lead white and red lead, were characterised using non-isothermal differential scanning calorimetry (DSC) in an air atmosphere to determine the effect of the pigment on the oxidati
Brown, LD, Ray, AS & Thomas, P 2004, 'Elemental analysis of Australian amorphous banded opals by laser-ablation ICP-MS', Neues Jahrbuch fur Mineralogie Monotshefte, vol. 9, pp. 411-424.
Brown, LD, Ray, AS & Thomas, PS 2004, 'Elemental analysis of Australian amorphous banded opals by laser-ablation ICP-MS', Neues Jahrbuch fur Mineralogie, Monatshefte, no. 9, pp. 411-424.View/Download from: Publisher's site
Several banded Australian opal-AG samples were analysed by laser ablation ICP-MS. The banded opals studied contained darker-coloured black or grey bands adjacent to lighter-coloured white or clear bands. The elemental distribution between bands indicated that darker-coloured bands contained significantly higher concentrations of transition elements (Ti, Co, V, Ni, Cu, Zn and Y) and rare-earth elements (La, Ce) than lighter-coloured bands. A solution depletion model, involving the charge-neutralisation of silica collóids by highly-charged transition metal cations, is proposed to explain these results. Irrespective of the origin of the opal, the distribution of trace elements for the white, translucent and play of colour opal bands was observed to be similar. This similarity was consistent with the proposed model. © 2004 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.
Liu, B, Thomas, P, Klimesch, DS & Ray, AS 2004, 'Fourier transform infrared evaluation of autoclaved cellulose fibre pulps used in cement-based building materials', Advances in Cement Research, vol. 16, no. 4, pp. 131-136.View/Download from: Publisher's site
Liu, B, Thomas, P, Ray, AS & Williams, RP 2004, 'The effect of sampling conditions on the thermal decomposition of electrolytic manganese dioxide', Journal Of Thermal Analysis And Calorimetry, vol. 76, no. 1, pp. 115-122.View/Download from: Publisher's site
The effect of sampling conditions on the decomposition of electrolytic manganese dioxide using thermal methods is reported. Significant differences were observed in the mechanism of the decomposition by simply changing the reaction environment from a closed pan to an open pan configuration. The purge gas atmosphere was also observed to influence the decomposition mechanism. As a product of the decomposition is oxygen, the change in the mechanism observed between the experimental conditions may be explained in terms of the ease of removal of oxygen from the reaction site.
Liu, B, Thomas, PS, Klimesch, DS & Ray, A 2004, 'Fourier transform infrared evaluation of autoclaved cellulose fibre pulps used in cement-based building materials', Advances in Cement Research, vol. 16, no. 4, pp. 131-136.View/Download from: Publisher's site
Brown, LD, Ray, AS & Thomas, P 2003, '29Si and 27Al NMR study of amorphous and paracrystalline opals from Australia', Journal Of Non-crystalline Solids, vol. 332, no. 1-3, pp. 242-248.View/Download from: Publisher's site
Four opal-AG (amorphous) and two opal-CT (paracrystalline) samples obtained from various regions in Australia were investigated with 29Si NMR and 27Al NMR. The proton cross-polarization 29Si NMR technique was used and the resulting spectra consisted of two main resonances: -102.0 and -111.2 ppm for opal-AG; and -102.5 and -112.2 ppm for opal-CT. These peaks were assigned to the Q3(1OH) and Q4 resonances, respectively. Using very short contact times, a third, very weak peak at -94 ppm was resolved in an opal-CT specimen, which was assigned to silicon in the Q2(2OH) arrangement (i.e. a silicon with twin hydroxyl groups). It was found that the opal-CT samples contained a higher proportion of both geminal and vicinal silanol groups (Q2 and Q3) than the opal-AG samples. The geminal silanol groups present in opal-AG and opal-CT are not restricted to opal-AN. The full-width at half-maximum (FWHM) values were 9.5 ppm for the opal-AG samples, and 6.5 ppm for both opal-CT samples, a result which confirms that opal-CT has a higher degree of short-range structural order than opal-AG. The 27Al NMR spectra of the opals all showed a single resonance at +52 ppm, indicating that the aluminium exists in a tetrahedral arrangement incorporated within the opal structure.
Simon, P, Thomas, P, Okuliar, J & Ray, AS 2003, 'An incremental integral isoconversional method - Determination of activation parameters', Journal Of Thermal Analysis And Calorimetry, vol. 72, no. 3, pp. 867-874.View/Download from: Publisher's site
An incremental integral isoconversional method for the determination of activation energy as a function of the extent of conversion is presented. The method is based on the treatment of experimental data without their transformation so that the resulting values of activation parameters should not be biased. The method was tested for recovering the activation energies from simulated data and employed for the treatment of experimental data of the NiS recrystallisation.
Thomas, P & Stuart, BH 2003, 'DSC characterisation of compression moulded PEEK-PTFE plaques', Journal Of Thermal Analysis And Calorimetry, vol. 72, no. 2, pp. 675-679.View/Download from: Publisher's site
Compression moulded plaques of a range of poly(ether ether ketone) (PEEK)- poly(tetrafluoroethylene) (PTFE) blends (100, 92, 48, 29, 9.5 and 0 mass% PEEK) have been characterised using differential scanning calorimetry (DSC) and wide angle X-ray crystallography (WAXD). A shift in the melting peak of the PEEK phase from 347 to 358°C was observed with increasing proportion of PTFE in the blend. A narrowing of the melting range was also observed. Correspondingly, WAXD measurements showed a reduction in the d-spacings. The observed changes in morphology are rationalised in terms of a higher degree of order imparted on the PEEK crystalline phase by the transmission of an applied 'hydrostatic' pressure by the presence of the PTFE.
Thomas, P, Hirschausen, D, White, RE, Guerbois, JL & Ray, AS 2003, 'Characterisation of the oxidation products of pyrite by thermogravimetric and evolved gas analysis', Journal Of Thermal Analysis And Calorimetry, vol. 72, no. 3, pp. 769-776.View/Download from: Publisher's site
Museum specimens of pyrite are known to undergo oxidation even during storage. Characterisation of the oxidation products is however not always simple due to amorphous character and varying degrees of hydration of the oxidation products. This paper presents an alternative approach to the characterisation of oxidation products by identifying their presence from their characteristic thermal decomposition processes using thermogravimetric and evolved gas analysis. Four pyrite specimens were characterised with varying degrees of oxidation. Iron(II) and iron(III) sulphates were also characterised for comparative purposes. The degradation products were observed to correlate well with the presence of iron(II) sulphate even though there was found to be some discrepancy in the higher temperature decomposition reactions.
Thomas, P, Simon, P & Ray, AS 2003, 'The effect of thermal history on the morphology of nickel sulphide', Journal Of Thermal Analysis And Calorimetry, vol. 72, no. 3, pp. 801-809.View/Download from: Publisher's site
The DSC characterisation of the morphology of the metastable a phase of stoichiometric nickel sulphide was carried out using two calorimeters; a TA Instruments 2920 MDSC and a Perkin Elmer DSC-7, and two quenching histories. Based on these quenching histories, significant differences were observed in the heat flow curves, including the observation of a second exothermic peak which is tentatively assigned to be a metastable phase to metastable phase transformation. The kinetic constants for the a to b recrystallisation were determined as a function of degree of conversion using a mechanism free isoconversional model. Variations in the values of the kinetic constants were also ascribed to the quenching histories. Although the differences in morphology observed were ascribed to the processing history, the shift in the position of the a to b recrystallisation peak was partially attributed to the thermal resistances of the instruments used.
Brown, LD, Ray, AS, Thomas, P & Guerbois, JL 2002, 'Thermal Characteristics of Australian Sedimentary Opals', Journal of Thermal Analysis and Calorimetry, vol. 68, no. 1, pp. 31-36.
Naturally occurring opals from three different regions in Australia were studied for their thermal characteristics. All the opals showed initial expansion followed by contraction in thermomechanical analysis (TMA) although the temperature at which the change from expansion to contraction occurred depended on their provenance. Thermogravimetric analysis (TG) revealed different rates and temperatures of dehydration for these opals. A general correlation between the temperature at which there was a zero thermal expansion and that of the maximum rate of dehydration was observed. A dehydrationsintering mechanism is proposed with the effect of sintering being more pronounced following total dehydration.
Bishop, D, Thomas, P, Ray, AS & Simon, P 2001, 'Two Stage Kinetic Model for the alpha-beta Phase Recrystallisation in Nickel Sulphide', Journal of Thermal Analysis and Calorimetry, vol. 64, no. 1, pp. 201-210.
Toughened glass panels used as a glazing material in multistorey buildings are known to fracture prematurely when they contain nickel sulfide inclusions as a result of the phase recrystallisation in nickel sulfide. The kinetics of this recrystallisation were studied by differential scanning calorimetry (DSC) under isothermal and non-isothermal conditions. The recrystallisation was observed to be a two-step process with an induction period followed by the phase change. A two-stage kinetic model was used to estimate the recrystallisation time under ambient conditions. These values were found to correlate well with the observed time to failure for glass panels installed in multistorey buildings.
Thomas, P, Guerbois, JL, Russell, GF & Briscoe, BJ 2001, 'FTIR Study of the Thermal Degradation of poly(vinyl alcohol)', Journal of Thermal Analysis and Calorimetry, vol. 64, no. 2, pp. 501-508.View/Download from: Publisher's site
The degradation of poly(vinyl alcohol) was investigated using TG analysis and Fourier transforminfrared spectroscopy to determine the effect of atmosphere on the process of degradation. Inthe spectra, four vibrational modes were identified that characterised the major steps of thedegradation process. These were the OH, CH, C=O and C=C stretching modes. Themechanism observed for degradation in an inert atmosphere was in accordance with theaccepted mechanism of elimination followed by pyrolisation. Evidence of conjugatedpolyenes, however, was not observed. For the air atmosphere, oxidation in both steps of thedegradation process was observed.
Bishop, DP, Thomas, P & Ray, AS 2000, 'Micro Raman characterization of nickel sulfide inclusions in toughened glass', Materials Research Bulletin, vol. 35, no. 7, pp. 1123-1128.View/Download from: Publisher's site
Toughened glass panels used as glazing material in multistory buildings are subject to fracture when they contain nickel sulfide inclusions. The failure mechanism is generally attributed to the significant volume increase related to a polymorphic phase retransformation in nickel sulfide. This investigation exploits the ability of micro Raman spectroscopy to analyze minute inclusions. The technique is able to distinguish between different polymorphs and various stoichiometric forms of nickel sulfide and has the potential to satisfy the need for an in situ, nondestructive analytical technique for the characterization of nickel sulfide inclusions in glass.
Partlett, M & Thomas, P 2000, 'Characterisation of Surface-Modified poly(ethylene terephthalate) Fibres by Inverse Gas Chromatography', Polymer International, vol. 49, no. 0, pp. 495-500.
Partlett, MJ & Thomas, PS 2000, 'Characterization of surface-modified poly(ethylene terephthalate) fibres by inverse gas chromatography', Polymer International, vol. 49, no. 6, pp. 495-500.View/Download from: 3.0.CO;2-X">Publisher's site
The effect of surface cleanliness on the alkaline hydrolysis of poly(ethylene terephthalate) fibres was investigated using inverse gas chromatography (IGC) in conjunction with mass loss measurements and electron microscopy. The sizing agent was removed from the fibre surface by two methods: soxhlet cleaning in acetone and washing in an aqueous solution of a non-ionic detergent. Alkaline hydrolysis was carried out using two concentrations of aqueous sodium hydroxide, 1% and 10% by mass. The measurement of the specific retention volume of undecane and the heat of adsorption using IGC indicated that the acetone cleaned samples were essentially surface contaminant free, while partial contamination of the surface by the sizing agent remained in the detergent cleaned samples. The presence of sizing agent significantly altered the degree of hydrolysis and the surface topography. The increasing values of the heat of adsorption indicated that significant surface hydrolysis increased the surface crystallinity.
Thomas, P & Ray, AS 2000, 'Processing initiated failure of toughened glass panels', Chemistry in Australia, vol. 67, no. 6, pp. 12-14.
Bishop, D, Thomas, P & Ray, AS 1999, 'Alpha-beta Phase Re-transformation Kinetics In Nickel Sulphide', Journal Of Thermal Analysis And Calorimetry, vol. 56, no. 1, pp. 429-435.View/Download from: Publisher's site
Nickel sulphide (NiS) was characterised using X-ray diffraction, thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). The as received Millerite, stoichiometric NiS, observed to be slightly nickel deficient, was found to readily
Bishop, DW, Thomas, PS & Ray, AS 1999, 'α-β phase re-transformation kinetics in nickel sulphide', Journal of Thermal Analysis and Calorimetry, vol. 56, no. 1, pp. 429-435.
Nickel sulphide (NiS) was characterized using X-ray diffraction, thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). The `as received' Millerite, stoichiometric NiS, observed to be slightly nickel deficient, was found to readily decompose in a nitrogen atmosphere at elevated temperatures (450 °C max.) to the sulphur deficient Godlevskite, Ni7S6, DSC and X-ray measurements demonstrated that the high temperature form of the Godlevskite was readily stabilized at room temperature. The kinetics of the α-β re-transformation in Godlevskite were then investigated using DSC and were observed to be first order.
The phase morphology of nickel sulfide (NiS) has received attention because of the possible correlation between fracture of toughened window glass panels and the alpha-beta phase transition. The detection of NiS in situ in glass, however, has proven diff
Smallwood, AG, Thomas, P & Ray, AS 1997, 'Characterisation Of Sedimentary Opals By Fourier Transform Raman Spectroscopy', Spectrochimica Acta Part A-molecular And Biomolecular Spectroscopy, vol. 53, no. 13, pp. 2341-2345.View/Download from: Publisher's site
The Fourier transform Raman (FT-Raman) spectra of a series of opals are presented. The opals characterised derive from a variety of origins in Australia and they are compared to opals originating from North America. The opals are distinguished by their c
Thomas, P & Stuart, BH 1997, 'A Fourier Transform Raman Spectroscopy Study Of Water Sorption By Poly(vinyl Alcohol)', Spectrochimica Acta Part A-molecular And Biomolecular Spectroscopy, vol. 53, no. 13, pp. 2275-2278.View/Download from: Publisher's site
The Fourier transform (FT) Raman spectrum of poly(vinyl alcohol) (PVA1) is reported. The spectra of PVA1 exposed to different aqueous environments are also reported. The changes to the FT Raman spectrum of PVA1 in the presence of water provide evidence o
Thomas, PS 1996, 'Dependence of the friction process on the molecular structure and architecture of thin polymer films', TRIBOLOGY INTERNATIONAL, vol. 29, no. 8, pp. 631-637.View/Download from: Publisher's site
The paper describes a peculiar transition in the interface rheology or frictional characteristics of high density polyethylene thin films. This transition is unusual in the sense that the transition is apparently from a ductile phase to a brittle phase as the temperature increases. The transition is observed to be a function of the contact pressure and strain rate. Again, and peculiarly, the transition is observed to decrease with an increase in both of these contact mechanical parameters. In addition, the vibrational spectra of HDPE as a function of temperature are examined in order to identify a mechanism for this transition. Due to the unusual nature of the transition, the mechanism sought is not at the molecular level, but is rationalised in term of the melting dynamics of the crystalline lamellae of HDPE. © 1995 Elsevier Science B.V.
Briscoe, BJ & Thomas, PS 1995, 'Structure-property relationships in thin solid poly(Methyl methacrylate) boundary films', Tribology Transactions, vol. 38, no. 2, pp. 382-388.View/Download from: Publisher's site
The interface properties of boundary films are commonly characterized try the measurement of the interface shear stress, t, xohich is defined as the frictional force per unit area of contact. The parameter t has been observed to be a strong function of several contact mechanical variables which include the contact pressure, the temperature, the sliding velocity and the contact time, t is also found to be a strong function of the processing methods used in the preparation of polymer films. It is this facet of the functionality of t that is pursued in the present paper with an emphasis upon the apparent ductile or brittle lubrication modes, the locus of the shear zone and the molecular architectures which are responsible for these resultant lubrication modes. © 1995 Taylor & Francis Group, LLC.
Stuart, BH & Thomas, P 1995, 'Xylene Swelling Of Polycarbonate Studied Using Fourier Transform Raman Spectroscopy', Spectrochimica Acta Part A-molecular And Biomolecular Spectroscopy, vol. 51, no. 12, pp. 2133-2137.View/Download from: Publisher's site
The Fourier transform (FT) Raman spectrum of polycarbonate (PC) is reported. The effect of xylene on the structural properties of PC has been investigated. Changes to the FT/Raman spectrum of PC in the presence of xylene are believed to be due to an incr
The paper speculates upon the molecular relaxation and dissipation mechanisms which may be responsible for the interface Theological characteristics of thin organic films. The molecular structure and interface rheology of a homologous series of poly(n-alkyl methacrylate)s are characterised for this purpose. These Theological properties are identified by the measurement of the interface shear strength, t as a function of the contact pressure. The molecular structure is deduced using vibrational spectroscopy. The Eyring model for molecular plastic flow is then applied and a correlation is drawn between the Theological and structural properties which are discussed in terms of possible mechanisms for the dissipation of the frictional energy. © 1994, Elsevier Inc. All rights reserved.
Briscoe, BJ, Thomas, PS & Williams, DR 1993, 'The Strain Rate Dependence of the Interface Shear Strength of Poly(methyl methacrylate) Films', Tribology Series, vol. 25, no. C, pp. 453-460.View/Download from: Publisher's site
The frictional response for a range of thin poly(methyl methacrylate) (PMMA) films has been assessed in terms of the interface shear strength, τ. The dependence of τ on the shear strain rate, the morphology and the molecular structure of the polymer have been experimentally determined. These dependencies are interpreted using a molecular topographical model of the interface shear process. This type of model allows the accommodation of microscopic shear stresses through molecular deformation in the polymer film. In order to identify the molecular nature of these processes, a theoretical stress activated model of molecular flow is employed. The structural properties of the polymer films, and, in particular, the conformation of the pendant ester group, are characterised by FTER. The current study proposes that the interface rheology of PMMA films is related to the conformation of the pendant ester groups attached to the carbon backbone chain of PMMA. © 1993, Elsevier Inc. All rights reserved.
BRISCOE, BJ, THOMAS, PS & WILLIAMS, DR 1992, 'MICROSCOPIC ORIGINS OF THE INTERFACE FRICTION OF ORGANIC FILMS - THE POTENTIAL OF VIBRATIONAL SPECTROSCOPY', WEAR, vol. 153, no. 1, pp. 263-275.View/Download from: Publisher's site
Briscoe, BJ, Stuart, BH, Thomas, P & Williams, DJ 1991, 'A Comparison Of Thermal-induced And Solvent-induced Relaxation Of Poly(ether Ether Ketone) Using Fourier-transform Raman-spectroscopy', Spectrochimica Acta Part A-molecular And Biomolecular Spectroscopy, vol. 47, no. 9-10, pp. 1299-1303.View/Download from: Publisher's site
The paper describes a study of the application of Fourier transform Raman spectroscopy as a means of identifying the extent of the surface plasticisation of a poly(ether ether ketone) by a known plasticising solvent, toluene. Spectra are described for t
Stuart, BH, Sullivan, C & Thomas, P 2016, 'An investigation of the degradation of polymeric grave goods in soil environments' in Kars, H & van den Eijkel, L (eds), Soil in Criminal and Environmental Forensics. Soil Forensics, Springer, Germany, pp. 331-341.View/Download from: Publisher's site
Plastic materials are a source of items that may be located in clandestine grave sites. Knowledge of their type and state of preservation or deterioration may provide a valuable resource for the identification of a victim or perpetrator. This study involves an examination of the effect of the nature of the soil environment on the structural properties of two common polymers, poly(vinyl chloride) and nylon, over a period of 18 months. These polymers represent common types of plastic sheeting and carpet material that may be used to wrap a body. Infrared spectroscopy and scanning electron microscopy have been used to monitor the structural changes that occur to these polymers in a soil environment and degradation mechanisms are proposed.
Thomas, PÅ, Sestak, J, Heide, K, Fuglein, EÅ & Simon, P 2011, 'Thermophysical Properties of Natural Glasses at the Extremes of the Thermal History Profile' in Sestak, J, Mares, JJ & Hubik, P (eds), Glassy, Amorphous and Nano-Crystalline Materials: Thermal Physics, Analysis, Structure and Propertie, Springer, Dordrecht, pp. 311-325.
Raja, S, Stuart, BH, Thomas, P & O'Brien, C 2010, 'Pyrolysis gas chromatography - mass spectrometry analysis for the estimation of pig bone age for forensic application' in Vieira, DN, Busuttil, A, Cusach, D & Beth, P (eds), Acta Medicinae Legalis et Socialis, Coimbra University Press, Coimbra, Portugal, pp. 11-14.View/Download from: Publisher's site
The potential of pyrolysis gas chromatography-mass spectrometry (Py-GCMS ) as a tool for the estimation of post-mortem age of bones has been investigated. Pig bone specimens prepared under controlled burial conditions in soil were studied and the post-mortem ages ranged from 3 to 48 months. Notable differences were observed in the data produced for younger bone specimens (<1 year) compared to specimens of greater post-mortem age (>1 year). Py-GCMS also demonstrates a relationship of particular peak ratios with the age of bones. The ratios of peaks in the pyrograms were examined and it was demonstrated that the ratios of certain pairs of peaks increase as the bone age increases.
Simon, P & Thomas, P 2009, 'Application of Isoconversional Methods for the Processes Occurring in Glassy and Amorphous Materials' in Sestak, J, Holocek, M & Malek, J (eds), Some thermodynamic, structural and behavioral aspects of materials accentuating non-crystalline states, Nymburk, Pilsen, Czech Republic, pp. 248-264.
Thomas, P, Heide, KÅ, estÃ¡k, J, FÃ¼glein, EÅ & imon, P 2009, 'Properties of Some Natural Glasses: Australian Opals and Czech Moldavites' in aroslav, ÅEK, Miroslav, HE & JiÅ, ÃML (eds), Some thermodynamic, structural and behavioral aspects of materials accentuating non-crystalline stat, Nymburk, PlzeÅ¿, pp. 200-218.
Ip, K, Ray, AS, Stuart, BH & Thomas, P 2005, 'Investigation of the degradation of sandstones in Sydney's heritage buildings' in Modena, C, Lourenco, PB & Roca, P (eds), Structural Analysis of Historical Constructions - Possibilities of Numerical and Experimental Techniques vol 1, Taylor & Francis, London, UK, pp. 239-244.
Sydney, with many of its heritage buildings and monuments constructed as a result ofthe first European settlement in the l800s, is a city built on a large block of sandstone. Although many ofthese buildings are still strong and sound, signs of deterioration have become evident in recent years. In order to prevent these precious buildings from further degradation, the weathering mechanisms of the stones must be thoroughly understood before suitable protection measures can be implemented. In this study, four techniques have been selected to detect chemical and physical differences between weathered and unweathered sandstones - Solid State Nuclear Magnetic Resonance (NMR) Spectroscopy, Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and X-ray Photoelectron Spectroscopy (XPS).
Nsiah-Baafi, E, Vessalas, K, Thomas, P & Sirivivatnanon, V 2019, 'Investigation of Alkali Threshold Limits and Blended Aggregate in ASR Risk-Assessed Concretes', Concrete New Zealand Conference, ConcreteNZ, Dunedin, New Zealand.
Concrete structures are designed for a specific design life to tolerate deterioration caused from various aggressive environmental loads such as carbon dioxide, chloride and aggressive soil conditions. The approach to prevent deterioration in concrete due to alkali-silica reaction (ASR) is by the avoidance of any such dissolution reaction taking place in concrete. ASR can in part be prevented by limiting the alkali content and restricting the use of potentially reactive aggregates. In this paper, the alkali threshold of several aggregates originating from New Zealand were determined using a modified version of RILEM AAR-3.2 and AAR-7.1. The AAR-2 accelerated mortar bar test (AMBT at 80°C) and AAR-3.2 concrete prism test (CPT at 38°C) were replaced with Australian Standard AS 1141.60.1 and 60.2 test methods, respectively, to evaluate expansion. Additional accelerated CPT in accordance with AAR-4.1 (ACPT at 60°C) was also conducted to examine the adequacy of shortening the test period. Petrographic examination taken before and after expansion testing was also carried out to qualify the presence of reactive silica and ASR gel contributing to expansion. The findings of this study suggest the potential for specifying the alkali threshold in concrete based on the reactivity classification of aggregates allowing a relaxation of the CCANZ Technical Report TR 3 alkali limit of 2.5 kg/m3 that is currently in place in New Zealand. This approach allows greater flexibility in the use of potentially reactive aggregates as sustainable concreting making materials.
Nsiah-Baafi, E, Vessalas, K, Thomas, P & Sirivivatnanon, V 2018, 'Mitigating Alkali Silica Reactions in the Absence of SCMs: A Review of Empirical Studies', The International Federation for Structural Concrete 5th International fib Congress, Melbourne.
The mechanism and severity of alkali-silica reaction (ASR) is subjective to the conditions of the availability of moisture and sufficient alkali content, and the presence of reactive aggregates. Since the 1940s, key focus has been placed on the reduction of alkali content by way of addition of supplementary cementitious materials (SCMs). However, the cost of SCMs and the realization that the availability of these materials could become limited in the untold future has influenced some researchers to investigate the development of protocols for the use of aggregates minimizing the likelihood of potential severe ASR. This paper presents a summary and review of the various strategies that have been adopted in recent years for the mitigation of ASR without utilising the addition of SCMs.
Roboredo, C, Thomas, P, Vessalas, K & Sirivivatnanon, V 2018, 'Alkali Limit In Cement With Supplementary Cementing Materials – A Review', The International Federation for Structural Concrete 5th International fib Congress, The International Federation for Structural Concrete Congress, Conrete Institute, Melbourne, Australia, pp. 1-8.
The alkali silica reaction (ASR) may cause deleterious cracking in concretes as a result of the reactions of reactive aggregates in concrete systems that contain elevated alkali contents. Current strategies applied in the mitigation of ASR are based on limiting the alkali content (Na2Oe) of the cement and concrete and through the screening of aggregates with additional surety provided by the use of supplementary cementitious materials (SCMs) in the partial replacement of cement. These strategies pose significant issues for the construction materials industry through increased manufacturing costs and reduction in volumes of viable raw materials that meet the imposed criteria. The effective mitigation of deleterious ASR using SCMs should change the focus of regulators and standards authorities to risk management through the assessment of the risk profile of a concrete mix in a particular application. Using a risk profile to assess alkali limits has the potential to relax alkali limits in cements. To achieve this aim a deep understanding of ASR in cement-SCM-aggregate concrete mixes is required through laboratory testing correlated with long-term field performance. This paper reviews ASR, reactivity assessment of aggregates and the role of SCMs in ASR mitigation and proposes a change in the focus to a balanced alkali limit based on assessed risk for the occurrence of deleterious ASR.
Tapas, M, Vessalas, K, Thomas, P & Sirivivatnanon, V 2019, 'An AMBT Study on the Effect of Limestone on ASR Mitigation: Ground Limestone Vs. Interground Limestone in Cements', Proceedings of the International Conference on Sustainable Materials, Systems and Structures (SMSS2019) Durability, Monitoring and Repair of Structures, International Conference on Sustainable Materials, Systems and Structures, RILEM Publications S.A.R.L., Rovinj, Croatia, pp. 201-207.
Tapas, M, Vessalas, K, Thomas, P, Sirivivatnanon, V & Kidd, P 2019, 'Mechanistic Role of Supplementary Cementitious Materials (SCMs) in Alkali-Silica Reaction (ASR) Mitigation', Concrete in Practice-Progress Through Knowledge, Sydney, Australia.
Alkali-silica reaction (ASR) can cause premature failure of concrete structures and therefore is a major concrete durability issue. The use of commonly available supplementary cementitious materials (SCMs) such as fly ash and slag is generally regarded as the most optimal and economical solution in mitigating ASR. However, the eminent closure of coal fired power stations in favour of greener technologies for producing energy and increasing demand in steel recycling threaten the future supply of SCMs that are currently available. Hence, the need to better understand the ASR mitigation process in order to be able to identify potential alternatives. This experimental study aims to provide a better understanding of ASR mitigation by studying the influence of various SCMs on ASR expansion, portlandite consumption and pore solution alkalinity. Results show that the efficacy of the SCMs in reducing ASR expansion can be correlated to their ability to consume portlandite and bind alkalis. Further, results suggest that any material that has high content of soluble Al2O3 and/or SiO2 is a potential SCM for ASR mitigation.
Thomas, P 2019, 'Application of Thermal Methods to the Characterisation of the States of Water in Precious Opal', CEEC-TAC5 & MEDICTA 2019, Central and Eastern European Committee for Thermal Analysis and Calorimetry and 14th Mediterranean Conference on Calorimetry and Thermal Analysis, Academica Greifswald, Rome, Italy, pp. 49-49.
Precious opal is a hydrous silica (SiO2.nH2O) that is formed through a dissolution-precipitation process forming hydrated silicas with variable water content . The gemmological value of precious opal is defined by its microstructure where the prized play-of-colour (POC) observed is a result of the diffraction of visible light from an ordered arrays of silica spheres. The monodispersed colloid of silica spheres are formed through an Ostwald type ripening process. Once the colloidal particles have grown to a suitable size for Bragg diffraction of visible light (ca. 200 to 400 nm in diameter; i.e. = 2dnsin where n is the refractive index of opal), aggregation occurs most likely through a homogeneous colloidal crystallisation process which results in the ordered array. Subsequently the array is solidified through precipitation of a second generation of silica which cements the array onto a solid coherent mineral specimen. The microstructure of the array can then be observed through the hydrofluoric etching of fresh fracture surfaces which reveal the ordered arrays of the monodispersed spherical particles.
As the process of opal formation occurs in solution, a hydrous silica is formed. The silica network itself can be of an amorphous nature (opal-A) or is paracrystalline (opal-CT; cristobalite containing tridymite stacking faults) and contains water in the form of molecular and silanol (bound) water. The molecular water is trapped in cages, capillary pores and interstitial voids while the silanol water is present at the surface, internal interfaces (e.g. at capillary or void surfaces) and in the silica network as isolated broken bridges. The type and amount of each of these species of water is dependent on the environment in which opal formation occurs (e.g. temperature and pH) and hence water may be used as a probe to characterise the morphology structure of opal.
Both thermal and spectroscopic methods have been used to successfully characterise the types of ...
Thomas, P & Boyd-Weetman, B 2019, 'Aggregate reactivity to the alkali-silica reaction (ASR) in ground aggregate-cement pastes', CEEC-TAC5 & MEDICTA 2019, 5th Central and Eastern European Conference on Thermal Analysis and Calorimetry (CEEC-TAC5) and 14th Mediterranean Conference on Calorimetry and Thermal Analysis (Medicta2019), Academica Greifswald, Rome, Italy, pp. 185-185.
A range of standard accelerated test methods for the screening of aggregates for susceptibility to the alkali-silica reaction (ASR) which causes deleterious cracking in concrete structures are available worldwide and two standard test have been recently adopted in Australia (AS 1141.60.1 (Accelerated mortar bar test (AMBT)) and AS 1141.60.2 (concrete prism test (CPT))). These accelerated test methods are empirical and based on expansion measurement correlated to field performance.
The mechanism of deleterious ASR resulting in cracking involves two processes; the chemical processes involved in the formation of the expansive ASR gel and the mechanical action of the ASR gel of the concrete in crack formation. Expansion tests, although empirical in nature are important as they probe the mechanical potential of the reactivity of aggregates. The chemical processes involved in the phase development are also important as they provide the gel responsible for cracking and understanding these processes canlead to more effective methods of mitigation of ASR as well as alternative methods for the screening of aggregates for reactivity to ASR. This paper focusses on correlating reactivity of aggregates determined using the standard test methods with phase development in paste tests using ground aggregate-cement pastes aged under accelerated conditions.
Two aggregates are investigated in this study, a micro-diorite (CPT non-reactive) and a greywacke (CPT reactive) which have been selected because of their relative reactivity to standard test methods. Both contain quartz as the phase potentially reactive to ASR. The aggregates were initially fine ground in a ring mill in order to make paste specimens using a general purpose Portland cement. Pastes specimens were prepared using a 3 to 1 aggregate to cement ratio with a water to cement ratio of 0.7. Pastes were initially hardened for 24 before stripping from the moulds and aging in alkali media (1 M NaOH) at elevated temperatu...
Thomas, P, Ha Hau, V, Vessalas, K, Sirivivatnanon, V & South, W 2019, 'Assessment of Aggregate Reactivity Using Slurry Tests', https://concrete2019.com.au/mobile/content.html, 29th Biennial National Conference of the Concrete Institute of Australia, Sydney.
The testing and screening of aggregates for their alkali-silica reactivity (ASR) is generally carried out initially by petrographic analysis. If reactive aggregates are identified by petrographic analysis then a rapid screening of the aggregate's potential to cause expansion using the accelerated mortar bar test (AMBT, AS-1141.60.1) is carried out to determine further reactivity potential. Aggregates that are found to be reactive in the AMBT method may be further screened using the concrete prism test (CPT, AS-1141.60.2). Both AMBT and CPT methods are a compromise between introducing accelerated and reactive conditions and monitoring the expansion over short and long periods of time but with conditions that are more closely aligned with field conditions.
Given that these tests are empirical estimates of reactivity potential, alternate testing may be developed for the screening of aggregates. Alternate laboratory tests are rapidly carried out using slurry tests on small samples of ground aggregate (e.g. ASTM C289). Simulating storage temperatures used in the AMBT (80°C) and CPT (38°C) in 1 M NaOH (1.25% Na2Oe) is an alternate approach to the development of new rapid screening tests. To assess the degree of aggregate reactivity a co-reactant, calcium hydroxide (CH), may be added to the reaction mixture aiding reactivity assessment through the consumption of CH. The results of a laboratory trial into the reactivity of aggregates using a ground aggregate slurry test of this nature are reported in this paper. The results are correlated with standard test method data using AMBT and CPT (AS-1141.60.1 and 2) with a view to assessing this method (or methods of this type) as an alternative rapid screening approach in the identification of aggregate reactivity for ASR potential.
Thomas, P, Roboredo, C, Boyd-Weetman, B, Vessalas, K, Farah, D & Sirivivatnanon, V 2019, 'Investigation of ASR Reactivity through Slurry Dissolution Tests', 29th Biennial National Conference of the Concrete Institute of Australia, Sydney.
The potential for alkali silica reaction (ASR) has been investigated through dissolution tests and the determination of the concentration of elemental species, Na, K, Ca and Si in the supernatant fluid of GP cement, aggregate and fly ash slurries. The aggregates selected for investigation were a reactive greywacke and a non-reactive micro-diorite both of which contain quartz. Alkali ions were delivered to the solution by the cement, although lower concentrations were released by both the aggregates and fly ash. Silica was released into solution according to aggregate reactivity. Rapid and local release of silica can yield an expansive ASR gel for reactive aggregate. Fly ash was observed to release silica rapidly indicating that the primary action of fly ash is through a competitive reaction for the formation of silica gel thus mitigating deleterious ASR. Quartz content as determined by X-ray diffraction analysis indicated that this phase was the main source of solution silica for the reactive aggregate.
Sanchez Roboredo, C, Thomas, P, Vessalas, K & Sirivivatnanon, V 2018, 'Advantages of Using High Alkali Cements and Industrial Waste Materials in Prevention of Alkali-silica Reaction in Concrete', Advancing Materials and Manufacturing CAMS2018 conference, University of Wollongong.
Thomas, P 2018, 'Water in Opal', 9th National Opal Symposium, Lightning Ridge, NSW, Australia.
Precious opal is a hydrous silica (SiO2.nH2O) and contains anywhere between 2 and 18% by mass water. Australian opal – AG contains circa 5.5 to 8.5% water with an average of 6.9% water while the water content of opal – CT derived from a range of sources from Australia and internationally is more variable and depends on the porosity of the opal.
The water contained in opal is of two general types; silanol or bound water (Si–OH) and molecular water (H2O). The silanol water can be found internally in the opal as well as on the surface. Internal silanol water is related to Si-O-Si linkages breaks, but they may also be associated with internal surfaces of capillary pores in the opal structure. The molecular water can be found trapped in the 3D superstructure of the silica network (hence the designation – AG or amorphous-gel like), in cavities or voids present between the spheres and in capillary pores. In Australian opal – AG, the molecular water is present trapped in the silica superstructure and in the voids between contacting silica spheres, although there is also some evidence of large capillary pore water. For opal – CT the picture is more complex and depends on the origin of the opal. Mexican, Ethiopian and Australian Tintenbar opal are all of the CT type and contain capillary pores in the smaller end of the scale. These pores contain much of the molecular water although there remains significant portion of the water trapped in the silica superstructure. In opal – CT, the capillary pores are often interconnected and are exposed to the surface as is demonstrated by the absorbent Ethiopian hydrophane opals where water is easily lost or absorbed. Given the variety of water types in opal, this presentation discusses the states of water with in opal – AG and – CT and then speculates on the role that water and microstructure has on the physical properties of opal.
Tapas, M, Vessalas, K, Thomas, P & Sirivivatnanon, V 2018, 'Role of Supplementary Cementitious Material Composition in its Efficacy to Mitigate Alkali-Silica Reaction', Concrete 2017 Advances in Materials and Structures, Adelaide, Australia.
Thomas, P, Ha Hau, WF, Vessalas, K, Sirivivatnanon, V & South, W 2017, 'Assessment of Test Methods for ASR Aggregate Reactivity', Concrete 2017 Advances in Materials and Structures, Adelaide, Australia.
The paper reports on the initial stages of a study into the use of phase analysis using typical laboratory techniques; thermogravimetric analysis (TG), infrared spectroscopy (FTIR) and x-ray diffraction (XRD) to investigate the alkali silica reaction (ASR) with a view to classifying the relative reactivity of aggregates. Phase analysis of ground aggregates reacted under AS1141.60.1 accelerated mortar bar test (AMBT) conditions in the presence of calcium hydroxide (CH) are reported for aggregates that have been identified as non-reactive, slowly-reactive and reactive according to the AMBT test. Results of the phase analysis correlated the AMBT classifications. The reactivity of the aggregates was also compared to the reactivity of a quartz flour of similar particle size distribution which was found to be less reactive than the reactive and slowly reactive aggregates. The reactivity of the quartz flour and the reactive and slowly reactive aggregate was attributed to the highly reactive conditions used.
Angus, KL, Thomas, P, Vessalas, K & Ray, AS 2012, 'Investigation of ground flint glass as a supplementary cementitious material in autoclaved lime-silica binders', From materials to structures: Advancement through innovation, Australasian Conference on the Mechanics of Structures and Materials, CRC press/Balkema, Sydney, Australia, pp. 247-249.
A potential application for the use of cullet glass is as a supplementary cementitious material (SCM). Cullet is a ground soda-lime-silica glass waste that has the potential to react with calcium hydroxide (CH) produced as a secondary product from the hydration of Portland cement (PC) in forming principal calciumsilicate- hydrate (C-S-H) strengthening phases. Additionally, the relatively high sodium content of the glass has the potential to act as precursor for the activation of aluminosilicates such as fly ash (FA). This paper investigates this potential by using these wastes in autoclaved hydrated lime CH-silica systems. Compressive strengths of autoclaved compacted cylinders were evaluated and the results demonstrate that the addition of ground glass provides higher strength, when used as a partial silica substitute, and aids in the activation of FA.
Fukumoto, T, Thomas, P, Simon, P & Stuart, BH 2013, 'Estimation of the curing rate of acrylamide used as a consolidant in heritage sandstone conservation', 4th Joint Czech-Hungarian-Polish-Slovak Thermoanalytical Conference Abstracts, 4th Joint Czech-Hungarian-Polish-Slovak Thermoanalytical Conference.
Galea, N, Hamedanimojarrad, P, Vessalas, K & Thomas, P 2012, 'Assessment of wollastonite microfibre on drying shrinkage behaviour of cement-based composites', From materials to structures: Advancement through innovation, Australasian Conference on the Mechanics of Structures and Materials, CRC press/Balkema, Sydney, Australia, pp. 499-504.View/Download from: Publisher's site
To date there has been limited research carried out on the effect of wollastonite as a microfibre addition to concrete or mortar and its effect on drying shrinkage behaviour. This investigation assesses the effect of wollastonite on drying shrinkage behaviour and compressive strength development of cement-based mortars. Mortar was selected for this study as a behavioural model since it is more sensitive to shrinkage strain than cement-based composites containing coarse-sized aggregate (concrete). Specimens were prepared with the addition of wollastonite at 2%, 4% and 6% by mass of cement. Key indicators of performance evaluated were change in length relative to control mortar exposed to the same storage conditions, as well as change in mass and compressive strength assessment at ages of 7 and 28 days. Results demonstrate that drying shrinkage decreases with the addition of wollastonite, while compressive strength increases with increasing age.
Ngadimin, A, Vessalas, K, Thomas, P & Hamedanimojarrad, P 2012, 'Investigation of flint glass for partial replacement of fine aggregate in fly ash cement-based mortars', From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, Australasian Conference on the Mechanics of Structures and Materials, CRC PRESS / BALKEMA, SYDNEY, AUSTRALIA, pp. 1159-1164.
This paper reports on the findings of an investigation into the evaluation of using flint glass (FG) sourced from post-consumer products, available in Australiaâswaste stream, as a replacement of fine aggregate in fly ash (FA) cement-based mortars.Workability, compressive strength and strength activity index were assessed in 3 phases of the research study, which includes: (1) partial replacement of sand by FG at 5%, 10% and 15%; (2) partial replacement of Portland Cement (PC) with FA at 10%, 20% and 30% using a fixed amount of FG; and, (3) variation of water/cementitious material ratio (w/cm) from 0.45 to 0.55 using a fixed amount of FA and FG. Results indicate that FG is suitable for partial substitute of fine sand in mortars up to 15% in terms of compressive strength; however, the value of strength attained is highly dependant on the w/cm used.
Fukumoto, T, Thomas, P & Stuart, BH 2012, 'The development of organic consolidants for heritage Sydney sandstones', 2nd International Congress - Chemistry for Cultural Heritage Abstracts, 2nd International Congress - Chemistry for Cultural Heritage Abstracts, Turkish Chemical Society, Istanbul, Turkey, pp. 1-1.
Fukumoto, T, Thomas, P, Stuart, BH, Ray, AS & Guerbois, JL 2012, 'Characterisation of poly(acrylic acid) - montmorillonite composites using TG-MS', 15th International Conference on Thermal Analysis and Calorimetry Abstracts, 15th International Conference on Thermal Analysis and Calorimetry.
Stuart, BH, Thomas, P & Hunt, AM 2012, 'The characterisation of ochres used in Australian Aboriginal paintings', 2nd International Congress - Chemistry for Cultural Heritage Abstracts, 2nd International Congress - Chemistry for Cultural Heritage.
Sullivan, CE, Stuart, BH & Thomas, P 2012, 'An investigation of the preservation of burial goods produced from modern materials', 6th European Academy of Forensic Science Conference Abstracts, 6th European Academy of Forensic Science Conference.
Fukumoto, T, Thomas, P, Stuart, BH, Adam, G, Simon, P, Shimmon, R & Guerbois, JL 2011, 'Kinetic and mechanistic analysis of the polymerisation of dimethylol urea', Proceedings of the 3rd Joint Czech-Hungarian-Polish-Slovak Thermoanalytical Conference, Slovak Chemical Society, Stara Lesna, pp. 1-5.
Hamedanimojarrad, P, Adam, G, Ray, AS, Vessalas, K & Thomas, P 2011, 'Development of Shrinkage Resistant Cement-based Materials Using Fibers', Modern Methods and Advances in Structural Engineering and Construction, International Structural Engineering and Construction Conference, Research Publishing, Zurich, Switzerland, pp. 1193-1198.View/Download from: Publisher's site
Drying shrinkage is themajor contributor to volume changes in normal strength concrete. Several classes of shrinkage compensating admixtures are known to the concrete industry. This study deals with the literature review and categorization of different classes of shrinkage reducing fibers, especially polyethylene fibers, with the objective of introducing new types of shrinkage reducing fiber. In this investigation a special type of hydrophobic polyethylene minifibers has been used in different dosages in mortar samples. The experimental results on drying shrinkage as well as on several other properties are reported. The hydro phobic minifibers showed remarkable improvement in shrinkage reduction even at very low concentrations (0.1%of cementweight).
Hamedanimojarrad, P, Adam, G, Ray, AS, Vessalas, K, Thomas, P & Nejadi, S 2010, 'A novel multi-functional expansive additive for drying shrinkage reduction in mortars', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), Australasian Conference on the Mechanics of Structures and Materials, CRC Press/Balkema, Melbourne, Australia, pp. 877-881.View/Download from: Publisher's site
Several shrinkage compensating additives and admixtures are currently used in mortar and concrete. This study deals with the literature review and categorization of different classes of expansive additives with the objective of introducing a new range of polymeric additive. In this investigation an inorganic polymer, which is a multifunctional expansive additive, was used in different mixes of mortar. The results of experiments on drying shrinkage as well as its effect on several physical properties are reported. The new polymeric additive used in the experiments were found to decrease the amount of drying shrinkage when compared with a control mixture through the reaction of the inorganic polymer with calcium hydroxide forming a stable binder as well as an expansive agent. This new additive also proved to have a positive effect on some fresh and hardened properties of mortar.
Hamedanimojarrad, P, Ray, AS, Adam, G, Thomas, P & Vessalas, K 2011, 'Evaluation of a hybrid system of admixture and fibre for development of shrinkage resistant cement-based material', 9th International Symposium on High Performance Concrete - Design, Verification & Utilization - Proceedings (TR48), International Symposium on High Performance Concrete, New Zealand Concrete Society (NZCS), Rotorua, NZ, pp. 1-8.
Shrinkage is a crucial feature in concrete and mortar members as it results in volume change that can lead to cracking and consequently to serviceability problems. Different additives and methods have been proposed to compensate for this problem mainly through the use of shrinkage reducing admixtures, fibres and expansive agents. In this paper, several combination systems of polyethylene micro-fibre along with an inorganic expansive agent have been studied for their influence on drying shrinkage. This special type of fibre, reported to act as shrinkage reducer, had been used in different concentrations in mortars and had been shown to have advantages and disadvantages. On the other hand, expansive agent, ammonium polyphosphate, had been shown to reduce drying shrinkage and modify most of mechanical properties. Free shrinkage strains as well as some physical properties of new mixes which contain polyphosphate and polyethylene micro-fibre are reported in this study. Several combinations were used and have been shown to have promising results in drying shrinkage, physical and mechanical properties.
Yang, L, Thomas, P & Stuart, BH 2011, 'DSC characterisation of thermally treated low density polyethylenes in a forensic context', Proceedings of the 3rd Joint Czech-Hungarian-Polish-Slovak Thermoanalytical Conference, Slovak Chemical Society, Stara Lesna, pp. 1-5.
Howes, JM, Stuart, BH, Thomas, P & Raja, S 2010, 'The analysis of forensic bones using Fourier transform infrared spectroscopy', 20th International Symposium on the Forensic Sciences Abstract Book, 20th International Symposium on the Forensic Sciences, Sydney.
Liu, B, Ray, AS & Thomas, P 2010, 'Drying shrinkage of hydrothermally cured cements with reactive magnesia and clay brick waste', Proceedings of the 12th International Inorganic-Bonded Fiber Composites Conference, International Inorganic-Bonded Fiber Composites Conference, Aalborg University, Aalborg, Denmark, pp. 90-95.
In recent years, worldwide research and development in the cement industry has gathered momentum with an aim to explore innovative and sustainable methods to deliver environmentally responsible Portland Cement (PC) based construction products. This study investigated physical and mechanical properties of autoclaved cement-quartz sand blends with the addition of clay-brick waste (CB waste) and reactive magnesia (MgO) with the aim to lower CO2 emissions through the reduction of PC consumption. Mechanical properties and drying shrinkage showed improvements with the incorporation of CB waste due to increased amounts and crystallinity of Al-tobermorite. The addition of reactive MgO to PC in hydrothermal conditions was observed to have a negative effect on the compressive strength. XRD data indicated that MgO did not take part in the reaction during the hydration of the cement and may even retard tobermorite formation. However, the expansive nature from the hydration of MgO to brucite may have compensated for drying shrinkage.
Raja, S, Stuart, BH, Thomas, P & Howes, JM 2010, 'The effect of soil burial environment on forensic bone structure', 20th International Symposium on the Forensic Sciences Abstract Book, 20th International Symposium on the Forensic Sciences, Sydney.
Raja, S, Stuart, BH, Thomas, P & Howes, JM 2010, 'The effect of soil burial environment on forensic bone structure', 20th International Symposium on the Forensic Sciences Abstract Book, 20th International Symposium on the Forensic Sciences, Sydney.
Vessalas, K, Ray, AS, Thomas, P, Joyce, PA & Haggman, J 2010, 'Pitchstone Fines: A New Inorganic Binder For Portland Cement-Based Construction Products', Proceedings of the 12th International Inorganic-Bonded Fiber Composites Conference, International Inorganic-Bonded Fiber Composites Conference, Aalborg University, Aalborg, Denmark, pp. 39-47.
The findings of this investigation into the performance pitchstone fines (PF) sourced from a naturally occurring pitchstone deposit in Queensland Australia as a potential pozzolanic supplementary cementitious material (SCM) are reported. 50 mm mortar cubes were prepared by replacement of 20% of the Portland cement (PC) with PF and PF blended with silica fume (SF) in a 1:1 ratio. Mortar cubes were also prepared with a 20% PC substitution level using fly ash (FA) and FA blended with SF also in a 1:1 ratio for comparison as the SCM. Control mortar cubes without PC substitution were also prepared. The compressive strength results for PF blended mortars were comparable to FA mortars, were within 75% of the control mortar at 7 and 28 days and approached the strength of the control mortar at 91 days curing. PF and FA blends containing SF produced compressive strength which surpassed the control mortar. Drying shrinkage measurements are also reported for up to 28 days storage in air. The PF mortar was found to have comparable shrinkage to the control mortar; the shrinkage of the FA mortar was found to be significantly greater. The differences were attributed to the particle shape, angularity and size resulting in greater capillary forces in the FA mortars resulting in greater shrinkage.
Raja, S, Stuart, BH & Thomas, P 2009, 'The development of analytical techniques for the determination of forensic bone age', 5th European Academy of Forensic Science Conference Book of Abstracts, 5th European Academy of Forensic Science Conference, Glasgow, pp. 1-1.
Raja, S, Stuart, BH, Thomas, P & Howes, JM 2009, 'The development of analytical techniques for the determination of forensic bone age', UTS Faculty of Science Research Day Book of Abstracts, UTS Faculty of Science Research Day.
Raja, S, Thomas, P & Stuart, BH 2009, 'A study of storage conditions and treatments for forensic bone specimens using thermogravimetric analysis', Medicta 2009 Book of Abstracts, 9th Mediterranean Conference on Calorimetry and Thermal Analysis, Marseille.
Raja, S, Thomas, P, Stuart, BH & O'Brien, C 2009, 'Pyrolysis gas chromatography - mass spectrometry analysis for the estimation of pig bone age', 21st Congress of the International Academy of Legal Medicine Abstracts, Congress of the International Academy of Legal Medicine, Lisbon.
Ray, AS, Connan, H, Liu, B & Thomas, P 2009, 'Alumina-Silica Rich Clay Brick Waste In Hydrothermally Treated Cement-Based Construction Products', Proceedings of the 34th Conference on Our World In Concrete & Structures, Conference On Our World In Concrete & Structures, CI-Premier Conference Organisation, Singapore, Singapore, pp. 289-296.
An urgent need for creative, sustainable approaches, which minimise the environmental impact of conventional Portland Cement (PC) -based construction materials, is recognised throughout the world. In recent years intensive research has been directed to the use of alumino-silicate materials to produce blended PC. The reduction of CO2 emissions, through the minimisation of PC consumption in the manufacture of PC-based construction products, and utilisation of industrial byproducts, to limit environmental impact, are the principal drivers of this worldwide activity. A number of supplementary cementitious materials (SCMs) containing alumina and silica such as fly ash, granulated blast furnace slag and silica fume are well known additives for the production of blended PCs due to their pozzolanic properties. The potential of other by-products such as those from the construction and demolition industry are less known however, even though they represent an excellent source of reactive alumina and silica-rich material. This paper deals with fired clay bricks (CB), generated as a waste product from construction and demolition activities, and their value as an additive in the manufacture of PC-based construction products. The research findings reported in this paper are from laboratory scale experiments conducted under hydrothermal conditions in an autoclave where fmely ground Cl3 waste was incorporated in the mixes. From a combination of analytical techniques including X-ray Diffraction, Differential Thermal Analysis, Scanning Electron Microscopy and solid-state Nuclear Magnetic Resonance, it was established that the aluminosilicate phase in the fired clay bricks promoted the development of the tobermorite, the principal binder in most calcium silicate products under hydrothermal conditions. The use of CB waste as a cement replacement for the manufacture of these products was also demonstrated as a viable option.
Vessalas, K, Ray, AS, Thomas, P, Joyce, PA & Haggman, J 2009, 'Assessment of chemical durability of pitchstone fines in Portland cement blended mortars', Concrete Solutions 09: Adding value in changing climates - Proceedings of the 24th Biennial Conference of the Concrete Institute of Australia, Concrete Solutions 09: Adding value in changing climates - 24th Biennial Conference of the Concrete Institute of Australia, Concrete Institute of Australia, Sydney, Australia, pp. 1-9.
The use of supplementary cementitious materials (SCMs) as partial replacement of Portland cement (PC) is an effective way of reducing the consumption of PC. This investigation is aimed at assessing some chemical durability aspects of PC-SCM blended mortars containing pitchstone fines (PF) and fly ash (FA) at 20% and 40% replacement levels of PC. Hardened mortar cubes containing these two pozzolanic SCMs and a control mortar containing 100% PC were prepared and pre-aged in lime-saturated water for 28-days. These specimens were then immersed into 1M solution of sodium sulphate (Na2SO4) and their mass and pH recorded after 28-days and 56-days. Specimens were also immersed in deionised water as a control environment for comparison of mass change and pH. In the case of PF, data from 1M Na2SO4 immersion demonstrate increasing substitution rate provides lower mass gain. In contrast, increasing replacement rate of PC by FA in 1M Na2SO4 demonstrates higher mass gain comparable to 100% PC.
Ip, KH, Stuart, BH, Thomas, PS & Ray, AS 2007, 'Thermal characterization of the clay binder of heritage Sydney sandstones', JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 8th Mediterranean Conference on Calorimetry and Thermal Analysis, SPRINGER, Palermo, ITALY, pp. 97-100.View/Download from: Publisher's site
Raja, S, Thomas, P, Stuart, BH & O'Brien, C 2008, 'Thermal analysis of bones in forensic applications', International Association of Forensic Sciences 18th Triennial Meeting Book of Abstracts, 18th Meeting of the International Association of Forensic Sciences, New Orleans.
Smallwood, AG, Thomas, P & Ray, AS 2008, 'The thermophysical porperties of Australian Opal', 9th International Congress for Applied Mineralogy, International Congress foe Applied mineralogy, Australasian Institute of Mining & Metallurgy, Brisbane, Australia, pp. 557-560.
Vessalas, K, Ray, AS, Thomas, P, Joyce, PA & Haggman, J 2008, 'Characterisation of Portland cement blended with pitchstone fines aiding carbon dioxide emission reduction', 9th International Congress for Applied Mineralogy, International Congress for Applied Mineralogy, Australasian institute of mining & Metallurgy, Brisbane, pp. 255-258.
Ip, K, Thomas, P, Stuart, BH & Ray, AS 2007, 'Thermal characterisation of the clay binder of heritage Sydney sandstone', Medicta 2007: The 8th Mediterranean Conference on Calorimetry and Thermal Analysis Book of Abstracts, 8th Mediterranean Conference on Calorimetry and Thermal Analysis, Palermo.
Onishi, A, Thomas, P, Stuart, BH, Guerbois, JL & Forbes, SL 2007, 'TGMS analysis of the thermal decomposition of pig bone for forensic applications', Medicta 2007: The 8th Mediterranean Conference on Calorimetry and Thermal Analysis, 8th Mediterranean Conference on Calorimetry and Thermal Analysis, Palermo.
Onishi, A, Thomas, P, Stuart, BH, Guerbois, JL & Forbes, SL 2006, 'TGMS analysis of the thermal decomposition of compact pig bone', 9th European Symposium on Thermal Analysis and Calorimetry, Wydawnictwo Naukowe, Krakow.
Friolo, KH, Stuart, BH, Ray, AS & Thomas, P 2005, 'Infrared spectroscopy of heritage building stones', Proceedings of the 6th Australian Conference on Vibrational Spectroscopy, ACOVS6 Organising Committee, Sydney.
Friolo, KH, Ray, AS, Stuart, BH & Thomas, P 2004, 'Degradation of historic sandstone buildings of Sydney', Proceedings of the 7th Australasian Masonry Conference, University of Newcastle, Newcastle, pp. 420-427.
Friolo, KH, Ray, AS, Stuart, BH & Thomas, P 2004, 'Thermal analysis of yellow block sandstones in Sydney's heritage buildings', 13th International Congress on Thermal Analysis and Calorimetry Book of Abstracts, 13th International Congress on Thermal Analysis and Calorimetry, Sardinia.
Ip, K, Ray, AS, Stuart, BH & Thomas, P 2004, 'Degradation of historic sandstone buildings of Sydney', Proceedings of the 7th Australasian Masonry Conference, Australian Masonary Conference, University of Newcastle, Australia, pp. 420-427.
White, RE, Phillips, M, Thomas, P, Wuhrer, R & Dredge, P 2004, 'Interactions between pigments in 19th and early 20th century oil paintings - in situ studies using environmental scanning electron microscopy', Proceedings Microscopy and Microanalysis 2004, Microscopy and Microanalysis, Cambridge University Press, Savannah, USA, pp. 132-133.View/Download from: Publisher's site
Thomas, P & Stuart, BH 2002, 'Crystalline morphology of PEEK in PEEK-PTFE blends', 8th Symposium on Thermal Analysis and Calorimetry Abstracts Book, 8th Symposium on Thermal Analysis and Calorimetry, Barcelona.
Bishop, DP, Thomas, P, Ray, AS & Simon, P 2001, 'Crystallisation of nickel Sulphide by Non-isothermal Cooling', Proceedings of Challenges for Coordination Chemistry in the new Century, Challenges for Coordination Chemistry in the new Century, Slovak Technical University Press, Slovakia, pp. 397-402.
Briscoe, BJ, Stuart, BH & Thomas, P 1993, 'Solvent induced morphological changes to polycarbonate', Polymer/Inorganic Interfaces: Materials Research Society Symposium Proceedings Vol. 304, Materials Research Society, San Francisco.
THOMAS, PS & WILLIAMS, DR 1993, 'THE CHARACTERISATION OF COATED POLYMERIC FIBRES BY INVERSE GAS CHROMATOGRAPHY', ADHESION SOCIETY PROCEEDINGS OF THE SIXTEENTH ANNUAL MEETING AND THE INTERNATIONAL SYMPOSIUM ON THE INTERPHASE, 16th Annual Meeting of the Adhesion-Society/International Symposium on the Interphase, ADHESION SOCIETY, WILLIAMSBURG, VA, pp. 120-122.