Infrastructure Engineering - Research Publications
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ItemStrength Development and Thermogravimetric Investigation of High-Volume Fly Ash Binders(MDPI, 2019-10)To address sustainability issues by facilitating the use of high-volume fly ash (HVFA) concrete in industry, this paper investigates the early age hydration properties of HVFA binders in concrete and the correlation between hydration properties and compressive strengths of the cement pastes. A new method of calculating the chemically bound water of HVFA binders was used and validated. Fly ash (FA) types used in this study were sourced from Indonesia and Australia for comparison. The water to binder (w/b) ratio was 0.4 and FA replacement levels were 40%, 50% and 60% by weight. Isothermal calorimetry tests were conducted to study the heat of hydration which was further converted to the adiabatic temperature rise. Thermo-gravimetric analysis (TGA) was employed to explore the chemically bound water (WB) of the binders. The results showed that Australian FA pastes had higher heat of hydration, adiabatic temperature rise, WB and compressive strength compared to Indonesian FA pastes. The new method of calculating chemically bound water can be successfully applied to HVFA binders. Linear correlation could be found between the WB and compressive strength.
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ItemNo Preview AvailableParametric study of the effect of thermal properties and ambient temperature on tensile stress and strength development in mass concrete(The International Federation for Structural Concrete (FIB), 2019-01-01)Thermal stress typically takes place at early ages when concrete is undergoing exothermic hydration reaction and is restricted from expansion and contraction by surrounding structural elements. In mass concrete structures, the relatively large temperature differences between the core and the surface produce differential dilation which leads to tensile stresses. Potential tensile cracks develop when the stress experienced by the concrete exceeds the concurrent strength of the maturing concrete. This effect in turn can lead to performance reduction, or in some instances, instability of structure and must be dealt with care. While published literature reports extensively on hydration based mechanical properties of concrete, only a few has considered investigating the in-situ performance of the material accounting for thermal stresses. In what concerns crack formation, consideration of the thermo-mechanical boundary conditions are important nuts that have not been investigated explicitly. This research aims to provide insight into the impacts of thermal related parameters on early age concrete crack formation through computational modelling.
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ItemHydration and Strength Evolution of Ternary-Blend High-Volume Fly Ash Concretes(American Concrete Institute, 2019-09-01)The increase of carbon emissions due to the annual growth of portland cement (PC) production has promoted research into the development of sustainable green concrete using a range of readily available industrial waste materials. The present study is focused on developing two high-volume fly ash (HVFA) concretes with cement replacement levels of 65% (HVFA-65) and 80% (HVFA-80). The required lime for both HVFA concrete mixtures was initially determined and the optimized mixture designs identified, based on the 28-day compressive strength, by varying the low-calcium Class F fly ash-hydrated lime composition. The optimized concrete mixtures achieved a compressive strength of 53 and 40 MPa (7.69 and 5.80 ksi) for HVFA-65 and HVFA-80 concretes, respectively. The early-stage strength development is dependent on the matrix produced in the specific HVFA concrete, which is itself dependent on the number of unreacted fly ash spheres. The increase of fly ash and hydrated lime dosage in HVFA concrete increases the rate of hydration of the C3A and C4AF phases, but decreases the hydration of the C3S phase, which resulted in lower early-age strength development than occurs in PC concrete. It was noted that the initial setting time of HVFA concretes increase with an increase of fly ash content. However, addition of hydrated lime accelerates the hydration and decreases the final setting time for HVFA concretes.
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ItemTransforming Municipal Solid Waste into Construction Materials(MDPI AG, 2019-05-09)Rapid urbanisation and the associated infrastructure development are creating a deficit of conventional construction materials and straining the natural resources. On the other hand, municipal solid waste (MSW) disposal poses a serious environmental problem. Landfilling of MSW is both costly and polluting. Incineration of MSW to generate energy is a commonly adopted approach. However, there are concerns associated with micro pollutants emitted from the combustion process. The carbon footprint of the process and the environmental cost–benefit balancing are disputable. There is clearly a need to adopt cost-effective alternatives to treat MSW. This paper proposes the potential application of “treated” MSW as an ingredient for construction materials. The treatment process involves placing MSW in an autoclave at 150 °C with 5 bars (0.5 MPa), followed by the separation of metals, plastics and glass for recycling purposes. The end-product, which is a semi-organic mixture (referred to as ‘biomass’), is passed through a vortex-oscillation system, which makes it more uniform as a material. Compressive testing of Portland cement-based pastes containing 10% and 15% biomass shows consistency in the results, demonstrating the potential use of biomass in construction materials.
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ItemNo Preview AvailableDuctility Design of Reinforced Very-High Strength Concrete Columns (100–150 MPa) Using Curvature and Energy-Based Ductility Indices(Springer Science and Business Media LLC, 2019-12-01)The paper aims to develop theoretical expressions for the ductility design of very-high strength concrete (VHSC) (> 100 MPa) columns using curvature and a new flexural energy-based ductility approach. Eventually, the study aims to evaluates the feasibility of VHSC columns for different ductility classes, considering the limitation of providing a higher volume of transverse reinforcement due to possible steel congestion in the construction phase. An analytical program based on the experimental stress–strain relationship of confined VHSC, which is validated using experimental programs on VHSC columns, is used to evaluate the ductility of VHSC columns for different parameters such as axial load ratio, confinement pressure, longitudinal steel ratio, yield strength of transverse steel, cover area and compressive strength of concrete. The theoretical curvature ductility and flexural rotation-based energy ductility of 3200 rectangular columns were evaluated using the analytical program. Using curvature ductility and the new flexural rotation-based energy ductility for different parameters, a regression analysis is carried out to develop expressions for the ductility design of VHSC columns up to 150 MPa. Using the new definition of energy-based ductility, a new expression is developed for limited ductility design of VHSC; and it is concluded that the new approach reduces the required amount of steel confinement due to an increase in the energy ductility of VHSC at higher axial load ratios and higher strengths. The studies show that reinforced VHSC can be used for structures with nominal ductility demands.
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ItemMaintenance of building structural systems(Nethwin Printers, 2016)The aim of this paper is to review the current literature on maintenance of building structural systems. It emphasises the importance of maintenance as an item for consideration from the beginning of the conceptual design stage. Building sustainability concept is generally understood to have better energy efficiency focus and maintenance of structural components ensures they serve their designed service life and beyond. The conventional design approach considers structural maintenance during the “product use” phase. This paper argues that if the accessibility of the building and maintenance (inspection, repair and retrofitting) are considered from the early conceptual design stage, it would save resources and maintenance cost. Case studies of buildings subject to earthquake loading and corrosion and their maintenance are presented.
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ItemBehaviour of Pre-Stressed High Strength Concrete Sleepers Subjected To Dynamic Loads(University of Queensland, 2015)
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ItemStrain Rates in Pre-stressed Concrete Sleepers and Effects on Cracking Loads(RMIT, 2014)Pre-stressed concrete sleepers (PCSs) play an essential role in railway track response, performance and safety. Depending on track condition and train speed, PCSs are subjected to high magnitude dynamic loads. These loads can generate cracks, which influence the stiffness, load bearing capability and durability of sleepers. The cracking of PCSs has been reported to be a major problem on a worldwide scale and imposes a costly replacement. This paper presents an investigation on the effects of calculating strain rates on the strength of PCS. By using available measurements, the strain rates are calculated at the rail seat and midspan, locations with a high concentration of stress. The cracking loads are calculated based on the dynamic increase factor (DIF) of concrete and comparison is made with commonly occurring dynamic loads. Results show that the maximum strain rates at both rail seat and midspan are about 0.08 and 0.016 1/s, respectively. The increase of cracking wheel load due to the strain rate effects is about 5 to 26 percent Further, the results are shown to be able to demonstrate the level of concrete damage in the form of cracks due to dynamic loads with very short return periods.