This paper presents an experimental study on the spalling characteristics, mass loss ratio, ultrasonic pulse velocity, compressive strength and flexural strength of self-compacting lightweight concrete (SCLC) at elevated temperature. Four types of SCLC specimens with and without polypropylene fibres (PPFs) and one type of normal concrete (NC) specimens were cast and tested. Based on the experimental observations and results, it was found that, compared with NC, SCLC spalls at a lower temperature but maintains a higher residual strength. For all the concretes the peak mass loss ratio increased but the relative ultrasonic pulse velocity decreased with the rise of temperature. At a given elevated temperature, the relative compressive strength and flexural strength of SCLC was larger than those of NC. The addition of PPFs greatly reduced the risk of spalling of SCLC. The thermal damage and the loss in residual mechanical properties of SCLC with PPFs were smaller compared with that without PPFs.

The attack of concrete owing to sulfate present in sewage is a major problem, both in Australia and worldwide. The prediction of the expected long-term performance of concrete exposed to sewerage and similar environments can be difficult as it is affected by a large number of parameters. In addition the deterioration process in concrete takes a long time to reach a significant level. Whereas considerable research has been undertaken in flowing sewage systems in pipes, little research has been undertaken on static systems contained in septic tanks. A research project conducted at RMIT University has investigated the deterioration of concrete septic tanks located in rural Victoria. A comprehensive set of laboratory experiments was established to measure the accelerated deterioration of concrete under exposure to sulfuric acid. The specimens were manufactured using the same mix design and ingredients used in septic tank production in rural Victoria prior to 1990. The mass changes in the concrete specimens have been recorded and based on the data, a statistical model has been developed to predict the mass change of concrete with time as a function of the cement content and acid concentration observed in sewage.

Lightly reinforced concrete walls are commonly found in low-to-moderate seismic regions such as Australia. While many theoretical analyses on lateral load–displacement of structural walls have been proposed and widely used, not many have been developed for lightly reinforced concrete walls. The lateral load–displacement behaviour and failure mechanism of lightly reinforced structural walls differ to those of heavily reinforced concrete walls, particularly in terms of tension stiffening effects, possible failure mechanisms and drift capacities. An analytical study on lightly reinforced rectangular concrete walls is presented in this paper. A parametric study was conducted to provide initial insight into the effect of four design parameters (aspect ratio, axial load ratio, transverse reinforcement ratio and longitudinal reinforcement ratio) on the ultimate displacement capacity of reinforced concrete walls. Two analytical models were developed to predict the lateral load–displacement behaviour of lightly reinforced walls consisting of a detailed wall model and a simplified wall model that provides a quick and conservative estimate for initial design checking purposes using displacement-based principles. Both models are shown to provide good agreement with experimental results in the literature.

Slag and fly ash were used in the fabrication of geopolymer concrete (GC). NaOH and Na₂CO₃ were used for slag and fly ash activation, and then highly fluidised C30 GC was prepared. Dynamic splitting-tensile tests were conducted using the ∅100 mm split Hopkinson pressure bar apparatus improved by the pulse shaper technique. The dynamic splitting-tensile mechanical properties of GC, including strength, deformation and energy dissipation, were then studied. In addition, the mechanism of the dynamic properties of the GC was analysed. The results indicate that dynamic splitting-tensile mechanical properties of GC exhibit a strong strain rate dependency. Strength and deformation increase approximately linearly with the logarithm of the average strain rate and, from an energy perspective, the correlation between energy dissipation and average incident pulse energy rate is obvious, the equation following a binomial curve; for GC, the strain rate sensitivity threshold is 5·027 s⁻¹. This research on dynamic splitting-tensile testing thus adds to a comprehensive understanding of the mechanical characteristics system of GC.

Prestress generally refers to the compressive prestress that is introduced by a compressive force beforehand to prevent tensile stress on the lower fibre of the bending member, and is often used in concrete girders. In girders with a smaller height compared to span length, compressive stress, which has a harmful impact on structural behaviour, is applied excessively to the girder's upper edge, limiting the reduction in girder height of the prestressed concrete girder. In this study, a prestress system integrating a tendon and two bars to support the compressive force in the girder's side ends was devised to offset the compressive force generated in the girder as a result of the introduction of prestress. To manage the jacking force of this system, formulae are proposed by theoretically clarifying the behaviour manifested during jacking in relation to the friction coefficient of the tendon and bars. A 10-m long rectangle-shaped girder is fabricated to check the friction coefficient of the bar and to verify the moment prestress method using the proposed double prestress system. Applicability to real structures is validated by measuring the behaviour manifested during the jacking of 35-m long real bridge girders.

Efficiency factors of steeply inclined unreinforced recycled aggregate concrete bottle-shaped struts have been experimentally found and compared with their natural coarse aggregate (NCA) concrete counterparts and the predictions of ACI 318–08, AASHTO bridge design specifications and Eurocode 2. The experiments involved testing of scaled deep beam specimens configured so as to develop bottle-shaped struts under applied loading. The replacement level of the coarse recycled concrete aggregate (RCA) in the saturated surface-dry moisture condition was the only parameter under investigation. Service load crack widths in the NCA and the RCA concrete bottle-shaped struts were smaller than the permissible value, their failure modes were similar, their measured efficiency factors were comparable and the coarse aggregate replacement level had an insignificant effect on the measured efficiency factors. The efficiency factor models in the ACI 318–08 and Eurocode 2, which are insensitive to strut inclination, gave overly conservative predictions, whereas relatively accurate predictions were obtained from the AASHTO bridge design specifications and an efficiency model given in the literature, both of which account for the effect of inclination on efficiency factors of bottle-shaped struts.