Can supervise: YES
Concrete technology, concrete durability, supplementary cementitious materials, cement chemistry, waste materials
Dong, W, Li, W, Lu, N, Qu, F, Vessalas, K & Sheng, D 2019, 'Piezoresistive behaviours of cement-based sensor with carbon black subjected to various temperature and water content', COMPOSITES PART B-ENGINEERING, vol. 178.View/Download from: Publisher's site
Moghaddam, F, Sirivivatnanon, V & Vessalas, K 2019, 'The effect of fly ash fineness on heat of hydration, microstructure, flow and compressive strength of blended cement pastes', Case Studies in Construction Materials, vol. 10.View/Download from: UTS OPUS or Publisher's site
© 2019 In this paper, an experimental study on the effect of fly ash fineness on the heat of hydration, microstructure, flow and compressive strength of blended cement pastes was carried out and evaluated against control cement paste. Fly ashes with different fineness: classified fly ash, run-of-station fly ash and grounded run-of-station fly ash; with a median particle size of 17.4, 11.3 and 5.7 μm, respectively, from the same power station source in Australia were used to partially replace Portland cement at 20% and 40% by weight of cement using a fixed water-to-binder ratio of 0.40. Results of this study showed that the cumulative heat of hydration of blended cement paste decreased as fly ash content in blended cement paste was increased. For a given cement replacement level, blended cement paste containing finer fly ash released more heat of hydration when compared to coarser fly ash. Moreover, increasing the fineness of fly ash resulted in a higher consumption of calcium hydroxide at 7 and 28 days reflecting pozzolanic reactivity and, thus, a denser microstructure than blended pastes containing coarser fly ash as revealed by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and compressive strength results. In addition, the incorporation of fly ash in the blended pastes led to the introduction of an additional hydration peak in the heat evolution curve possibly due to the late activation of fly ash by calcium hydroxide renewing the C 3 A reaction and converting ettringite to monosulfate. The flow of the freshly blended cement pastes was also found to improve slightly with increasing fineness of the fly ash. In addition, the hardened blended cement pastes containing 20% ground run-of-station fly ash showed comparable compressive strength with the control cement pastes at both 7 and 28 days mainly due to the higher fineness of the ground run-of-station fly ash and increased reactivity compared to coarser grade fly ash.
Almabrok, MH, McLaughlan, R, Vessalas, K & Thomas, P 2019, 'Effect of oil contaminated aggregates on cement hydration', American Journal of Engineering Research (AJER), vol. 8, no. 5, pp. 81-89.View/Download from: UTS OPUS
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
Almabrok, M, McLaughlan, R & Vessalas, K 2018, 'EFFECT OF SYNTHETIC DRILL CUTTINGS ON MORTAR PROPERTIES', Malaysian Journal of Civil Engineering, vol. 30, no. 3, pp. 405-414.View/Download from: UTS OPUS or Publisher's site
Drill cuttings from oil exploration are recognised as a major environmental concern. Current cost-effective treatment technologies often involve sending treated products to landfill without any potential end-use thereby rendering these solutions unsustainable. There is potential
for using drill cuttings comprising of oily, saline and clayey waste materials as fine aggregate replacements in structural concretes requiring characteristic compressive strength from 20-32 MPa. Research into the hydration process as well as evaluating the fresh and hardened properties
of mortars incorporating synthetic drill cuttings were undertaken. Replacement of sand by
synthetic drill cuttings (up to 25% by weight) produced mortar with accelerated hydration as well as reduced flow and density. In addition, the 28-day compressive strength of mortar incorporating synthetic drill cuttings decreased by up to 50%. Satisfactory strength for all sand replacement levels evaluated in mortars was still attainable for reuse of these synthetic of drill cuttings as fine aggregate replacements in structural concretes.
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.View/Download from: UTS OPUS
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.
Mohammadreza Hassani, E, Vessalas, K, Sirivivatnanon, V & Baweja, D 2017, 'Influence of permeability-reducing admixtures on water penetration in concrete', ACI Materials Journal, vol. 114, no. 6, pp. 911-922.View/Download from: UTS OPUS or Publisher's site
Copyright © 2017, American Concrete Institute. All rights reserved. An experimental investigation was carried out on concrete into the effectiveness of integral permeability-reducing admixtures as possible alternatives to the traditional external waterproofers. The efficiency of hydrophobic water repellents and crystalline pore blockers were evaluated in concretes incorporating fixed water-cementitious materials ratio (w/cm) and different cementitious material types covering OPC, fly ash, and granulated blast-furnace slag. Three different test methods were employed to evaluate the water penetration resistance of concrete. To isolate the benefits that are achieved by varying the mixture design parameters, statistical factorial analysis of variances was carried out to discover the significance of each variable. Results indicated that the effect of w/cm and cementitious material is more pronounced compared to the addition of permeability-reducing admixtures. It was also demonstrated that the admixtures can be effective in reducing water penetration; however, their effect is varied in different mixtures. Caution must be exercised when using such admixtures in different concrete mixtures.
Mohammadi, I, Khabbaz, H & Vessalas, K 2016, 'Enhancing mechanical performance of rubberised concrete pavements with sodium hydroxide treatment', Materials and Structures/Materiaux et Constructions, vol. 49, no. 3, pp. 813-827.View/Download from: UTS OPUS or Publisher's site
© 2015 RILEM This research evaluates performance of rubberised concrete prepared with sodium hydroxide (NaOH) treated rubber. Numerous studies have investigated the method of treating rubber with NaOH. However, the level of improvement achieved by this method has not been consistent between different studies. Hence, it is worthwhile to study application of this treatment method. Ten series of concrete specimens with different water cement ratios and a variety of rubber content were prepared. The fresh and hardened mechanical tests were conducted on concrete samples. It was found that the duration of 24 h for treatment of crumb rubber was the most promised duration, which resulted in favourable fresh and hardened concrete characteristics. Compared to rubberised concrete prepared with untreated rubber, rubberised concrete prepared with the 24-h NaOH treated method had 25 and 5 % improvement in compressive and flexural strength, respectively. It is experimentally indicated that using this treatment method resulted in notable improvement for the compressive strength, and moderate enhancement in the flexural strength.
McLaughlan, RG, Almabrok, MH & Vessalas, K 2015, 'Effect of Curing and Mixing Methods on the Compressive Strength of Mortar Containing Oil', UNIMAS e-Journal of Civil Engineering, vol. 6, no. 1, pp. 6-11.View/Download from: UTS OPUS
Oil contaminated fine aggregate is a major environmental concern and can arise as a by product of industrial activities (e.g. oil well
drilling and land contamination). Cement–based stabilisation/solidification of oil contaminated materials is an emerging technology
however there are some issues that have not been fully addressed. This paper reports the results of a study conducted to investigate the
effect of different curing and mixing methods on cement solidification and its consequent effect on the compressive strength of the
resultant cementitious product. This work has been done to address leaching concerns during the curing period. The normal curing method
for samples to be tested for compressive strength is lime saturated water. However, this method invalidates any subsequent leaching tests.
Accordingly, bag curing (BC) and lime saturated water curing (LSW) have been applied using mortar mixed with mineral oil up to 10% by
sand mass under water wet (WW) or oil wet (OW) mixing methods. The results indicate that development in 28 day compressive strength
can be achieved without applying water by external means if the moisture movement from the mortar samples is prohibited, irrespective of
the mixing methods used.
McLaughlan, RG, Almabrok, MH & Vessalas, K 2015, 'Evaluating the effect of mixing method on the performance of mortar containing oil', International Journal of Engineering Science Invention, vol. 4, no. 3, pp. 58-64.
There is a vital need for managing oily materials resulting from the petroleum industry as their
toxic and persistent nature threatens the environment. In view of oil waste remediation, current treatment
technologies are either cost prohibitive and/or the treated products have to be sent to landfill without any
potential end-use. Cement-based stabilisation/solidification of oil contaminated materials is an emerging
method however there is limited knowledge in terms of the effect of the mixing method on the properties of the
resultant cementitious mix. For this purpose, the water wet (WW) and oil wet (OW) protocol was devised to see
if the observed behaviour of the mortar was a function of the mixing method rather than the ingredients. A
cement-based mortar incorporating a mineral oil addition of up to 10% of the aggregates mass was used. The
results indicated that the mixing method has only a small effect on the fresh and hardened properties. Increased
oil content in the cement mortar was found to increase the flow and setting time whereas there was decreased
wet density and air content irrespective of the type of the mixing method used. The compressive strength
decreased by 75% and 77% for water wet and oil wet respectively compared to the control at 28 days of age.
The mixing method has a relatively small impact overall on the hydration process. The calorimetry results
showed that both mixing methods followed the same trend whereby the hydration is inhibited due to oil
Noushini, A, Samali, B & Vessalas, K 2015, 'Ductility and Damping Characteristics of PVA-FRC Beam Elements', ADVANCES IN STRUCTURAL ENGINEERING, vol. 18, no. 11, pp. 1763-1787.View/Download from: Publisher's site
Mohammadi, I, Khabbaz, H & Vessalas, K 2014, 'In-depth assessment of Crumb Rubber Concrete (CRC) prepared by water-soaking treatment method for rigid pavements', Construction and Building Materials, vol. 71, pp. 456-471.View/Download from: UTS OPUS or Publisher's site
Noushini, A, Vessalas, K & Samali, B 2014, 'Rheological properties and compressive strength behaviour of polyvinyl alcohol fibre-reinforced concrete', Australian Journal of Structural Engineering // the Institution of Engineers, Australia, vol. 15, no. 1, pp. 77-88.View/Download from: Publisher's site
Comprehensive experiments were carried out to assess the effects of uncoated polyvinyl alcohol (PVA) fibres of two geometric lengths (6 and 12 mm) on the fresh and hardened properties of concrete. Fly-ash was also used as partial replacement of Portland cement in all mixes. Based on total concrete volume, four fibre fractions of 0.125%, 0.25%, 0.375% and 0.5% were evaluated for their effect on slump, compacting factor, air content, mass per unit volume, compressive strength, relative strength with age and mode of failure in PVA fibre-reinforced concretes (FRCs). PVA fi bres were observed to decrease the slump and mass per unit volume of FRC, while increasing the compressive strength up to 56 days ageing. With regards to workability and compressive strength, optimum fibre addition was established for 0.25% PVA-FRC incorporating 6 mm fibres with a 12% increase noted in compressive strength compared to the control concrete at 28 days ageing.
Noushini, A, Vessalas, K & Samali, B 2014, 'Static mechanical properties of polyvinyl alcohol fibre reinforced concrete (PVA-FRC)', Magazine of Concrete Research, vol. 66, no. 9, pp. 465-483.View/Download from: UTS OPUS or Publisher's site
This investigation assessed the performance of polyvinyl alcohol (PVA) fibres of 6 mm and 12 mm length in concrete. Based on total concrete volume, four fibre fractions (0.125, 0.25, 0.375 and 0.5%) were evaluated for their effect on fresh and hardened properties of PVA fibre reinforced concretes (PVA-FRCs). Fly ash was also used as partial replacement of Portland cement in all the mixes. By carrying out a comprehensive set of experiments (compressive strength, splitting tensile strength, modulus of elasticity, modulus of rupture and residual flexural strength), it was observed that PVA fibre significantly enhances the static mechanical properties of concrete as well as improving its post-peak response and ductile behaviour.
Noushini, A, Vessalas, K & Samali, B 2014, 'Static mechanical properties of polyvinyl alcohol fibre reinforced concrete (PVA-FRC)', Magazine of Concrete Research, vol. 66, no. 9, pp. 465-483.View/Download from: Publisher's site
Noushini, A, Vessalas, K, Arabian, G & Samali, B 2014, 'Drying shrinkage behaviour of fibre reinforced concrete incorporating polyvinyl alcohol fibres and fly ash', Advances in Civil Engineering, vol. 2014, pp. 1-10.View/Download from: Publisher's site
The current study assesses the drying shrinkage behaviour of polyvinyl alcohol fibre reinforced concrete (PVA-FRC) containing short-length (6 mm) and long-length (12 mm) uncoated monofilament PVA fibres at 0.125%, 0.25%, 0.375%, and 0.5% volumetric fractions. Fly ash is also used as a partial replacement of Portland cement in all mixes. PVA-FRC mixes have been compared to length change of control concrete (devoid of fibres) at 3 storage intervals: early-age (0-7 days), short-term (0-28 days), and long-term (28-112 days) intervals. The shrinkage results of FRC and control concrete up to 112 days indicated that all PVA-FRC mixes exhibited higher drying shrinkage than control. The shrinkage exhibited by PVA-FRC mixes ranged from 449 to 480 microstrain, where this value was only 427 microstrain in the case of control. In addition, the longer fibres exhibited higher mass loss, thus potentially contributing to higher shrinkage. © 2014 Amin Noushini et al.
Noushini, A, Samali, B & Vessalas, K 2013, 'Effect of polyvinyl alcohol (PVA) fibre on dynamic and material properties of fibre reinforced concrete', Construction And Building Materials, vol. 49, no. 1, pp. 374-383.View/Download from: UTS OPUS or Publisher's site
The effect of uncoated polyvinyl alcohol (PVA) fibre addition on dynamic properties of fibre reinforced concrete (FRC) has been investigated in the current study. PVA fibres of two geometric lengths (6 and 12 mm) with aspect ratio of 428 and 857, respectively, were utilised. Fly ash was also used as partial replacement of Portland cement in all mixes. Based on total concrete volume, two fibre fractions of 0.25% and 0.5% were evaluated for their effect on fundamental frequency, dynamic modulus of elasticity and damping ratio of FRC. 28-Day static mechanical properties are also measured. From the results, it can be stated that although PVA fibre addition in low volume fractions used in this study significantly enhance the mechanical properties of FRC, it has no considerable effect on concrete material damping characteristics.
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.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
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).
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.View/Download from: UTS OPUS
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.
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: UTS OPUS or 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.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
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.
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, Melbourne.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
Thomas, P, Ha Hau, V, Vessalas, K, Sirivivatnanon, V & South, W 2019, 'Assessment of Aggregate Reactivity Using Slurry Tests', 29th Biennial National Conference of the Concrete Institute of Australia, Sydney.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
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.
Vessalas, K, Nsiah-Baafi, E, Thomas, P & Sirivivatnanon, V 2019, 'Investigation of Alkali Threshold Limits and Blended Aggregate in ASR Risk-Assessed Concretes', Concrete New Zealand Conference 2019, Dunedin, New Zealand.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
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.View/Download from: UTS OPUS
Gardner, AP & Vessalas, K 2016, 'Experiences with flipped learning in a postgraduate subject in civil engineering', 44th Annual Conference of the European Society for Engineering Education - Engineering Education on Top of the World: Industry-University Cooperation, SEFI 2016, SEFI - Annual Conference of European Society for Engineering Education, SEFI, Tampere, Finland.View/Download from: UTS OPUS
The design of a flipped learning environment typically blends online and face-to-face activities. A major affordance of this type of learning environment is the opportunity to use class time for students and the instructor/s to participate in collaborative learning activities .
The consensus in the literature is that lecturing is not the most effective instructional method and that active learning activities are more effective [2–4]. Flipped instruction makes time for active learning activities in face-to-face class sessions by introducing subject content before the face-to-face session, typically through online resources such as readings, videos, simulations and/or quizzes. Previous research  showed that postgraduate students preferred the flexibility of flipped learning over traditional transmission-based subject design.
This paper describes how the postgraduate subject Concrete Technology and Practice at the University of Technology Sydney was redesigned to create a flipped learning environment. The focus of the flipped design was to develop students’ contextual critical thinking skills and apply these skills to issues encountered in professional practice. This paper will focus on three key aspects of this transformation namely feedback, collaborative ways of working for students and the instructor, and the time involved for the instructor.
Noushini, A, Samali, B & Vessalas, K 2013, 'Effect of Polyvinyl Alcohol (PVA) Fibre on the Dynamic Properties of Concrete Containing Fly Ash', Composite Construction in Steel and Concrete VII, International Conference on Composite Construction in Steel and Concrete, ASCE, Palm Cove, Australia, pp. 456-467.View/Download from: UTS OPUS or Publisher's site
The object of the present investigation is to study the effect of polyvinyl alcohol (PVA) fibres on dynamic properties of concrete containing fly ash as partial replacement for portland cement. Specimens of different concrete types, with variations in the length of fibers and proportioning, have been investigated to assess the performance of uncoated PVA fibre of two geometric lengths (6 and 12 mm) in concrete. Based on total concrete volume, 2 fibre fractions of 0.25 and 0.5%, were evaluated for their effect on damping ratio, fundamental frequency and dynamic modulus of elasticity of PVA fibre reinforced concretes (FRCs). From the results, it can be stated that although PVA fibre addition in low volume fractions used in this study significantly enhance the mechanical properties of FRC, it has no considerable effect on concrete material and RC beams dynamic characteristics - See more at: http://ascelibrary.org/doi/abs/10.1061/9780784479735.035#sthash.wtcmL7a…
Gardner, AP, Goldsmith, R & Vessalas, K 2016, 'Using practice architectures theory to compare consecutive offerings of the same subject', Proceedings of the 27th Annual Conference of the Australasian Association for Engineering Education (AAEE2016), Australasian Association of Engineering Education annual conference, Southern Cross University, Coffs Harbour.View/Download from: UTS OPUS
Two consecutive offerings (2015 and 2016) of the same subject, Concrete Technology and Practice, prompted opposite reactions from students. The academics involved in 2015 and/or 2016 sought to explore the similarities and differences between these consecutive offerings in reflecting on the learning and teaching practices in their classroom.
Practice architectures theory provides a framework for examining and understanding the differences between these consecutive offerings of ostensibly the same subject. This paper also provides an example of how a theoretical framework can be used to examine teaching practices – even our own by practitioners who are also acting as researchers in this context.
Evidence used in comparing the 2015 and 2016 offerings of this subject is drawn from focus group discussions with students and observations of each of the researcher/practitioners involved. Additional data includes the end of semester Student Feedback Survey results including written responses to open-ended questions.
Differences in aspects of the cultural-discursive, material-economic and socio-political arrangements of the 2015 and 2016 offerings of Concrete Technology and Practice became apparent from the analysis.
Using the theory of practice architectures gave us insights into the inter-relationships between the different arrangements inherent in teaching and learning practices. It also highlighted the resilience of ‘taken for granted’ practices.
Hassani, M, Baweja, D, Vessalas, K & Schmidt, Z 2015, 'Benefits of Permeability Reducing Admixtures to Watertight Concrete', 27th Biennial National Conference of the Concrete Institute of Australia in conjunction with the 69th RILEM Week, Concrete Institute of Australia, Procs 27th Biennial National Conference of the Concrete Institute of Australia in conjunction with the 69th RILEM Week.
Brennan, J, Ding, G, Wonschik, C-R & Vessalas, K 2014, 'A closed-loop system of Construction and Demolition Waste Recycling', Proceedings of the 31st International Symposium on Automation and Robotics in Construction and Mining, International Symposium on Automation and Robotics in Construction, University of Technology, Sydney, 15 Broadway, Ultimo NSW 2007, Australia, Sydney, Australia, pp. 499-505.View/Download from: UTS OPUS or Publisher's site
This study discusses the construction and demolition waste recycling stream both in Australia and in Germany. Differences and commonalities in commercial practices between the two countries are outlined, and open research questions are introduced. Following McDonough and Braungart’s cradle-to-cradle theorem, and ideal closed-loop system within the building life cycle is proposed. Deficiencies and efficiencies in the closed-loop system are reported and assessed and related parameters promoting or hindering the closed-loop system are evaluated. Results of the study demonstrate that reusable and non-reusable materials generated from construction and demolition operations, which are destined for landfill, are categorized differently between the recycling systems used in Australia and Germany.
Gardner, AP, Willey, K, Vessalas, K & Li, J 2014, 'Experiences with flipped learning in subjects in consecutive stages of aCivil Engineering programme', Proceedings of the 25th Annual Conference of the Australasian Association for Engineering Education, AAEE - Annual Conference of Australasian Association for Engineering Education, School of Engineering & Advanced Technology, Massey University, Wellington, NZ.View/Download from: UTS OPUS
Flipped learning is an instructional approach which allows instructors the opportunity to use a blending of online and face to face learning activities. The main affordance of flipped learning is the opportunity to free up class time to allow students and instructors to engage in collaborative learning activities designed to consolidate and deepen conceptual understanding of the subject material. Research has shown that participating in flipped instruction can change the way students approach their studies and improve motivation.
PURPOSE OR GOAL
We are interested in students’ experience of the flipped environment, particularly their expectations of a learning environment, and the level of responsibility they take for their own learning. The purpose of this analysis is to create a baseline against which future instances of flipped learning can be compared.
Student perceptions of flipped instruction were investigated through survey responses and observations of students in a first year subject (Engineering Mechanics) a second year subject (Engineering Computations) and a third year subject (Construction Materials) in a Civil Engineering degree programme. In particular, students were asked to explain the impact of the flipped activities on their learning experience including any changes in how they approach their studies or managed their time.
Most students in each of the three subjects agreed that they ‘liked’ flipped instruction compared to the traditional lecture format. The majority of students in each subject also agreed that it is reasonable to expect students to prepare before attending a face to face session. However, some students made strong negative comments demonstrating how the flipped environment did not meet their expectations of how learning should be organised. This study suggests that students in the second and third year subjects were not necessarily showing signs of better self-regulation and time management sk...
Ghosni, N, Samali, B & Vessalas, K 2014, 'Evaluation of structural behaviour of polyproylene Fibre Reinforced Concrete Beam Under Cyclic Loading', Proceedings of the 23rd Australasian Conference on the Mechanics of Structures and Materials, Australasian Conference on the Mechanics of Structures and Materials, Southern Cross University, Byron Bay, Australia, pp. 319-326.
Hassani Esgandani, M, Vessalas, K, Baweja, D & Schmidt, Z 2014, 'Effect Of Chemical Admixtures On Water Penetration Of Concrete', Proceedings of RILEM International workshop on performance-based specification and control of concrete durability, RILEM International workshop on performance-based specification and control of concrete durability, RILEM, Zagreb, Croatia, pp. 209-216.View/Download from: UTS OPUS
Durability of concrete is in part determined by its resistance to the penetration of deleterious substances entering as a liquid or gas that is considered to be a function of its permeation capacity. Permeation capacity is controlled by the connectivity of pores that exist in the cementitious matrix and paste-aggregate boundaries. The presence of chemical admixtures in a mixture can greatly reduce the permeation capacity of hardened concrete by several orders of magnitude. Permeability-reducing admixtures are effective in blocking capillary pores by making them hydrophobic as well as depositing pore-blocking products into the pores.
This paper presents an experimental study into the effectiveness of using permeabilityreducing admixtures including hydrophobic pore blockers and crystalline self-sealers. Concretes with increasing w/c ratios of 0.4, 0.5 and 0.6 have been investigated. The effect of admixtures on water penetration has been assessed through monitoring the changes in mass transport mechanisms. In addition to the available standard test methods, the coefficient of permeability of water has been directly determined using a specially developed test method described in this paper. Results indicate that permeability-reducing admixtures can reduce the water penetration of concrete significantly if used correctly and if the design intent is defined.
Wonschik, C-R, Brennan, J, Ding, G, Heilmann, A & Vessalas, K 2014, 'Implications of legal frameworks on construction and demolition waste recycling - a comparative study of the German and Australian systems', Proceedings: ISARC 2014, International Symposium on Automation and Robotics in Construction, The International Association for Automation and Robotics in Construction (IAARC), Sydney, Australia, pp. 523-530.View/Download from: UTS OPUS or Publisher's site
This comparative study between German and Australian legislation demonstrates that legal frameworks impact on the way in which recycling systems work. Both Australia and Germany operate as Federations and the autonomy of states influences common federation wide practices and standards. In Germany’s case however, it is obliged to comply with European Union guidelines which result in German federal legislation being binding for all German states and to common industry practices across all of Germany. Purely industry regulated systems are not always sufficient to cater for societal and environmental needs, and political intervention can sometimes be necessary to achieve desired outcomes. The construction and demolition (C&D) waste recycling industry is a good example. In Australia C&D waste recycling is mostly industry regulated, while the state has greater influence in Germany. A statistical analysis illustrates legislative impact on recycling outcomes. Nonetheless, any legislative efforts can also have effects contrary to the intended ones. A study of such cases is conducted and other influencing factors also considered. In conclusion, the study outlines the importance of interstate coordination and regulation; and the need for the incorporation of industry requirements and other potentially influencing factors into the legal frameworks in order to meet desired outcomes.
Almabrok, M, McLaughlan, RG & Vessalas, K 2012, 'Characterisation of cement mortar containing oil-contaminated aggregates', 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. 1091-1096.View/Download from: UTS OPUS
Oil spills, leakage and other releases of products from petroleum industry are a source of contamination and are recognised as a major environmental concern. The current treatment technologies for these materials are either cost prohibitive and/or the treated products have to be sent to land fill without any potential end-use, thereby rendering these solutions unsustainable. Cement-based stabilisation/solidification is an emerging technology; however there is currently quite limited knowledge on the effect of oil on the cement solidification process and its consequent effect on the performance of fresh and hardened properties of the resultant cementitious mix. The purpose of conducting this study is to determine the appropriateness of the mortar for various end-uses when incorporating mineral oil additions up to 10% of the aggregate mass. Increased oil content in the cement mortar was found to increase setting time and decrease air content. The compressive strength decreased by 78% compared to the control at 28 days age. However, since the compressive strength covered a wide range of values, various feasible end-use scenarios for oil contaminated mortar exist.
Ghosni, N, Samali, B & Vessalas, K 2013, 'Ductility and strength of reinforced concrete beams intrinsically reinforced with polypropylene fibres', Proceedings of the 13th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2013, East Asia-Pacific Conference on Structural Engineering and Construction, Sapporo, Japan.View/Download from: UTS OPUS
One of the horizons through which a more cost effective concrete can be conceived and be able to satisfy constructional requirements as well as modern society's demand, would be the Green Concrete concept. It has been for decades that sustainable design is drawn into direct attention of different sectors of society. From the structural point of view, the invaluable goal of this project is to improve the ductility of the concrete structural element which helps eliminate or reduce the need for steel reinforcement in concrete structures. Trend of improvement in human knowledge is promising and so far this project, like other projects with the same aim, is contributing to inevitable changes in the construction industry. Cracking in reinforced concrete causes stiffness reduction which is the reason for decreasing the capacity of the structure in bearing structural loadings. Concrete is a brittle material and its failure is mostly due to this characteristic. Different methods have been used to overcome this problem and give ductility to concrete matrix. Using short fibres like steel fibres or synthetic fibres and polymeric material is of attention to improve this behaviour of concrete. The effect of these additives is more on the post peak behaviour of concrete which improves the strain softening where tension is applied. Fibres within the matrix, can bridge the cracks which improves the performance of concrete matrix and results in a better stress bearing material. Different types and percentages of polypropylene fibres have been investigated for the mechanical properties of concrete. From among these mixes two best are selected and reinforced beams are casted to be tested under four point bending test. Results show that by using high percentage of PP fibre in the reinforced concrete beam, ductility can be improved by 160 %.
Ghosni, N, Samali, B & Vessalas, K 2013, 'Energy Absorption and Flexural Toughness Evaluation of Fibre Reinforced Polymer Modified Concrete', Proceedings of the 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), International Center for Numerical Methods in Engineering (CIMNE), Toledo, Spain, pp. 1122-1130.View/Download from: UTS OPUS
This paper presents the effect of fibres on the behaviour of fibre reinforced concert (FRC) which nowadays is recognised for its energy absorption capacity as well as other benefits. Incorporating fibres in concrete, results in an ameliorated mix design which can dissipate energy and improve the fracture performance of concrete matrix. There are different types of test methods developed to measure the concrete energy absorption capacity, one of which is the four point bending test. This research work is on the flexural behaviour characterisation of polymer modified synthetic fibre reinforced concrete incorporating polypropylene (PP) fibres and styrene butadiene (SB) latex copolymer. Results of this study show that by adding PP fibres to concrete, toughness and energy absorption characteristics can be enhanced. By increasing the amount of fibre used in the concrete matrix this value can be increased. It has also been concluded that by adding fibres to the concrete matrix, the energy absorption characteristics can consequently be improved.
Ghosni, N, Samali, B & Vessalas, K 2012, 'Evaluation of mechanical properties of carpet fibre reinforced concrete', From materials to structures: Advancement through innovation, Australasian Conference on the Mechanics of Structures and Materials, CRC press/Balkema, Sydney, Australia, pp. 275-279.View/Download from: UTS OPUS or Publisher's site
Incorporating suitable material in concrete to improve its performance is an important consideration in the construction industry. Using short fibres as an additive to improve its mechanical properties has been of great attention. Different types of fibres can be used as intrinsic reinforcement to enhance concrete performance. Some of the fibres used in concrete are recycled waste materials such as carpet fibres. This paper aims to investigate the static properties of fibre reinforced concrete (FRC) utilising short carpet fibres shredded and prepared from the carpet industry waste. Thereafter, the economic considerations regarding use of carpet fibres in concrete are discussed. There have not been any comprehensive studies on the effectiveness of carpet fibres in concrete, whereas there is a more comprehensive literature available for other types of fibres such as steel fibres. The effect of adding recycled carpet fibres on the strength development of FRC have been studied and the results are compared to control concrete. Fresh properties i.e. slump, air content and wet density and hardened properties i.e. compressive strength and modulus of rupture after 7 and 28 days of ageing are reported.
Ghosni, N, Vessalas, K & Samali, B 2012, 'Evaluation of fresh properties effect on the compressive strength of polypropylene fibre reinforced polymer modified concrete', 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. 1123-1127.View/Download from: UTS OPUS
Investigations on the characteristics of Fibre Reinforced Concrete (FRC) have gained momentum in the last fewdecades. Employing suitable polymeric fibres and additives in concrete to improve its performance is an important consideration in the construction industry. This research aims to investigative the effect of polypropylene (PP) fibre volume percentage within the concrete mix with and without the presence of polymeric materials on the rheological properties of concrete and its behaviour under compression. PP fibres exhibit low elastic modulus, high elongation and are of low cost, making these fibres most suitable for inclusion in Polymer Modified Concrete (PMC). Traditionally, PP fibres are used in concrete to reduce plastic shrinkage and micro cracking. Accompanying PP fibre additions to PMCs are often styrene butadiene (SB) copolymer latex additions; used to improve the bonding of PP fibres in the cementing matrix. This paper reports on the findings of using different percentages of PP fibres with PMCs incorporating 10% SB latex and 30% fly ash (FA) for partial replacement of Portland cement. Slump, mass per unit volume, air content, high range water reducer agents amount and compressive strength, will be assessed and compared to plain concrete devoid of PP fibre, SB latex and FA additions, after period of curing applied at 7, 28 and 56 days of ageing.
Hassani Esgandani, M, Vessalas, K, Baweja, D & Schmidt, Z 2014, 'Assessment of watertight concrete and role of chemical admixtures', Concrete Institute of Australias Biennial National Conference 2013, Concrete Institute of Australia - Biennial Conference, Concrete Institute of Australia¿s, Gold Coast, Australia.View/Download from: UTS OPUS
Noushini, A, Samali, B & Vessalas, K 2013, 'Damping properties of polyvinyl alcohol fibre reinforced concrete', Proceedings of the 13th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2013.
This paper presents results of an experimental investigation evaluating dynamic properties and damping ratio of fibre reinforced concrete (FRC) including PVA fibres of two different geometric lengths, 6 and 12 mm, with volume fraction of 0.25% and 0.50%. The impact resonance test is used to determine the resonant frequency of 75 × 100 × 400 mm prisms by applying a small load impulse and measuring the resulting acceleration through the specimen for transverse mode of vibration. For each concrete type, impact resonance test was carried out at 14 and 28 days of ageing. From the test results, the fundamental (natural) frequencies are measured and acceleration-time history graphs are prepared. Acceleration-time history is used in order to calculate the damping ratio, following logarithmic decrement method. The dynamic modulus of elasticity (DMOE) is also being calculated from the fundamental transverse frequency which is comparable to the static chord modulus of elasticity. The compressive strength of concretes at the age 28 day is also evaluated. Test results indicated that the compressive strength of concrete increased by fibre addition. However, it has been observed that PVA fibre addition in low volume fraction used in this study do not significantly affect the concrete modulus of elasticity and damping ratio.
Noushini, A, Samali, B & Vessalas, K 2013, 'Flexural Toughness and Ductility Characteristics of Polyvinyl-Alcohol Fibre Reinforced Concrete (PVA-FRC)', Proceedings of the 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), International Center for Numerical Methods in Engineering (CIMNE), Toledo, Spain, pp. 1110-1121.View/Download from: UTS OPUS
This paper presents the results of an experimental study investigating the effect of uncoated polyvinyl alcohol (PVA) fibres on the properties of hardened concrete. PVA fibre of varying lengths, 6 and 12 mm and aspect ratio (l/d) of 430 and 860, respectively, was utilised in different volume fractions of 0.125%, 0.25%, and 0.5%. In addition, 30% fly ash was also used as partial replacement of Portland cement in all fibre reinforced concrete (FRC) mixes. Uniaxial compression, splitting tensile, modulus of rupture (MOR) and modulus of elasticity (MOE) tests were performed following the Australian Standards to evaluate the mechanical poperties of PVA-FRCs. Fracture test is also conducted in accordance with European Standard in order to evaluate the residual flexural tensile strength and limit of proportionality of PVA-FRCs. Furthermore, the structural properties of reinforced concrete (RC) beams incorporating PVA fibres are investigated for their load-deflection behaviour using 4-point loading. Flexural toughness of the test specimens and peak load deflection were measured and discussed indicating to what extent the un-coated PVA fibre can enhance the brittle-like behaviour of concrete. Results show that adding PVA fibres to the mix generally improves the mechanical properties of concrete. Regarding the strength, the optimum fibre content goes to 0.25% for both fibre lengths and in the case of toughness and ultimate deflection 0.5% shows the highest values. An increase of 30% in ductility is noted for the RC beam incorporating 0.5% by volume fraction of 12 mm PVA fibre.
Noushini, A, Samali, B & Vessalas, K 2013, 'Influence of polyvinyl alcohol fibre addition on fresh and hardened properties of concrete', Proceedings of the 13th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2013, East Asia-Pacific Conference on Structural Engineering and Construction, Sapporo, Japan.View/Download from: UTS OPUS
This investigation assesses the performance of using uncoated poly-vinyl alcohol (PVA) fibres of two geometric lengths (6 and 12 mm) in concrete. Based on total concrete volume, 3 fibre fractions of 0.25%, 0.5% and 1% were evaluated for their effect on fresh and hardened properties of PVA fibre reinforced concretes (FRCs). By carrying out a comprehensive set of experiments, an effective method of mixing fibre was adopted (based on modification of the Australian Standard AS 1012.2 test method). In comparison to control concrete (devoid of PVA fibre), slump and mass per unit volume were found to decrease while air content remained similar with increasing fibre addition. Optimum fibre addition was established for 0.25% PVA-FRC with 16% improvement noted in compressive strength compared to control concrete at 28 days. Relative strength gain from 7 to 28 days was also observed to be higher for all PVA-FRCs.
Noushini, A, Vessalas, K, Ghosni, N & Samali, B 2012, 'Effect of polyvinyl alcohol fibre and fly ash on flexural tensile properties of concrete', 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, Sydney, Australia, pp. 1165-1170.View/Download from: UTS OPUS or Publisher's site
This paper investigates the effect of synthetic fibre and fly ash (FA) on post peak response and fracture properties of concrete. Polyvinyl alcohol (PVA) fibres were added as intrinsic reinforcement to concrete and30%of cementwas replaced with fly ash as an environmental friendly additive to reduce cement consumption. Samples were prepared abiding by relevant standards and tested accordingly. Limit of Proportionality (LOP) of the mentioned concretes has been assessed. Notched rectangular prisms have been tested to evaluate the residual flexural tensile strength and limit of proportionality of conventional and FA modified concrete as well as fibre reinforced concrete (FRC). Cylindrical samples have been tested to determine the compressive strength and indirect tensile strength of each concrete. Tests have been conducted at 28 days of ageing. Results gathered from different mix designs are compared to control and other mixes.
Satsangi, R, Vessalas, K & Russell, S 2012, 'Assessment of bottom ash use as fine aggregate replacement in concrete', 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. 1183-1186.View/Download from: UTS OPUS
Concrete is the most common construction material used worldwide. Fine aggregate constitutes approximately 25% of the total volume of concrete. Currently, most fine aggregate used in concrete consists of naturally occurring sands, which are sourced from sand quarries. In the future, Sydney will face a sand shortage, with most quarries becoming exhausted. This will likely lead to increased demand in using sands hauled from longer distances, adversely impacting the environment. This project investigates the feasibility of using bottom ash (BA) as a novel sand replacement in concrete. BA is defined as a by-product of coal burning power stations. The BAs used in this study were sourced from 3 different power stations in NSW to assess the practicality of using BA for replacement of sand in concrete. Compared to control concrete, Bayswater BA concretes showed improved performance at 20% replacement of sand content with higher compressive strength and lower drying shrinkage.
Sharifi, N, Vessalas, K & Samali, B 2012, 'Assessment of compressive strength of elastomeric modified concrete incorporating waste tyre rubber', 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. 1187-1191.View/Download from: UTS OPUS or Publisher's site
This paper reports on the fundamental findings of utilizing Styrene Butadiene Rubber (SBR) waste tyre granules as a potential source for replacing coarse aggregate in elastomeric modified concrete (EMC). EMCs incorporating 2%, 4%, 6% and 10% of SBR granules (12-15 mm) are assessed for their fresh and hardened properties compared to control concrete devoid of SBR granule additions. Fresh concrete was investigated for slump, air content, and wet density while hardened concrete was evaluated for compressive strength at 7, 28 and 56 days of age. A decrease in slump, density up to 4% and compressive strength of 10 to 44% for 28 days of age, with the addition of SBR granules and an increase in the value of air content were observed.
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.View/Download from: UTS OPUS
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.
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: UTS OPUS or 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.View/Download from: UTS OPUS
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.
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: UTS OPUS or 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: UTS OPUS or 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.View/Download from: UTS OPUS
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.
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.View/Download from: UTS OPUS
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.
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.
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.View/Download from: UTS OPUS