Mortar in masonry structures can be subjected to both uniaxial and triaxial loading. Determining the mechanical properties and/or failure criteria of the commonly used mortar is necessary for the structural performance assessment of new and existing masonry buildings using non-destructive testing and/or finite element modelling methods. In this paper, the stress–strain behaviour of a commercially available cement-lime mortar is investigated under uniaxial and triaxial loading. The axial compressive strength, modulus of elasticity, Mohr–Coulomb failure envelopes of the mortar are determined over a range of conditions. Mortar specimens were prepared with a water to cementitious material ratio (w/cm) of 0.6–0.7 and were tested at curing ages of 3, 7, 14, and 28 days, under confining pressures of 0, 100, 250, 500 and 750 kPa. Ultrasonic pulse velocity (UPV) of the specimens were measured before the destructive testing. The results indicate that the influence of curing age and confining pressure on the axial compressive strength of the mortar can be predicted using proposed linear correlations between (i) The confining pressure and the axial compressive strength and (ii) The UPV and the axial compressive strength. From the test results, the strength parameters of the Mohr–Coulomb failure criterion were also determined. It is observed that cohesion is more sensitive to changes in curing age and w/cm than the friction angle, which varied between 32 and 33 degrees.

External post-tensioning can be considered an effective strengthening method for bridge members, which are deteriorating due to extreme loading conditions and progressive structural aging. The effects of existing shear cracks in bent caps strengthened by external post-tensioning were experimentally investigated using model specimens. Initial investigation revealed that the shear capacity of a bent cap is not enhanced by external posttensioning only, when shear cracks exist. Moreover, it was found that the repair of existing cracks using epoxy injection substantially increases the shear capacity of the bent cap. The Tenthill Creek Bridge in South EastQueensland, Australia provides a case study where the bent caps have been strengthened by external posttensioning. The model tests of the bridge bent caps confirmed the initial findings on the effects of existing shear cracks on the shear capacity. The experimental results emphasize the need for appropriate repair of existing shear cracks prior to strengthening by external post-tensioning to enhance the shear capacity of bent caps.

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As a part of a large research program aiming at the cementitious materials containing recycled materials at Central Queensland University – Australia, the current paper presents the preliminary results of a study on the effects of fly ash, which is used to replace cement in concrete, on the concrete compressive strength. For this purpose, systematic experiments have been carried out to investigate the influences of fly ash ratio and age. The compressive strength of concrete specimens with replacement ratios of 15%, 30% and 45%, and aged 7 and 28 days are measured and are compared with those of the concrete specimens without fly ash at the same ages. The results demonstrate that the strength of fly ash containing concrete improves more slowly but more strongly with aging, than their fly ash free counterparts, and an optimum fly ash replacement ratio exists where the maximum compressive strength of fly ash containing concrete can be achieved, and the maximum strength for the specimens aged 28 days and above is higher that of fly ash free concrete. Furthermore, the observation strength behaviours are analysed and discussed in terms of the influences of fly ash on interface reactions and interface bonding strength.