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The instability of earth structures resting on granular materials, such as embankments and tailing dams, is caused by the infiltration of water which can lead to their failure. This paper presents the potential use of tyre crumbs for controlling the stability of structures made of sand. Constant shear drained experiments were carried out on mixtures of sand and tyre crumbs to understand the onset of instability. Conventional drained shear tests were carried out on all samples up to a deviator stress of 200 kPa. Tests were then carried out on the sheared samples by reducing the confining pressure until the onset of instability. This was determined by a drop in stress, by second-order work and by the strain ratio approach. The value of mean effective stress at instability was found to decrease with the addition of tyre crumbs to the mix of up to 20% and then increase with further addition of tyre crumbs. The strain ratio approach was found to predict the onset of instability easily and efficiently, similar to the second-order work method.

Cross-sectional analyses of circular and square reinforced concrete (RC) columns strengthened with reactive powder concrete jacketing and fibre-reinforced polymer (FRP) wrapping were undertaken. The stress block method was used to determine theoretical axial load–bending moment (AL–BM) interactions of the columns. These were then compared with experimental results and found to be in very good agreement. A parametric study was also undertaken to investigate the most important factors that influence the AL–BM capacity of circular and square strengthened columns. Finally, a group of theoretical AL–BM interactions for circular and square strengthened columns was produced. These can be used in a wide range of applications for strengthening RC columns with high-performance concrete jackets and FRP wraps.

Past studies suggested various methods to determine the onset of instability of soil under constant shear drained (CSD) stress path using triaxial equipment. These methods were based on the characteristic features observed on the CSD stress path, axial and volumetric strains. However, the characteristic features are not similar for every soil leading to inconsistencies in predicting the onset of instability under the CSD stress path. This paper presents a strain ratio (εv/εa) – mean effective stress (p′) based method for determining the onset of instability of sand in the CSD stress path. The proposed method identifies the onset of instability at the drop of the εv/εa–p′ curve and features a distinctive value to mark the onset of instability. A series of CSD tests have been carried out on sand samples to verify the applicability of the proposed method. The proposed method captured the onset of instability similar to the other methods available in the literature.

This study presents an analytical model for the load-moment (P-M) interaction diagrams of circular geopolymer concrete (GPC) columns reinforced with glass fiber-reinforced polymer (GFRP) bars and GFRP helices. The analytical P-M interaction diagrams of GPC columns were developed using the layer-by-layer numerical integration method. The analytical predictions of GFRP reinforced GPC columns were then validated against the experimental results on the behaviour of GFRP reinforced GPC columns under different loading conditions. It was found that the developed analytical model predicted the load and moment capacities of GFRP reinforced GPC columns with good accuracy. Further, a parametric study showed that the influence of increasing the compressive strength of GPC was more pronounced on P-M interaction diagrams of GPC columns under concentric and low levels of eccentric axial loadings. Also, the increase in longitudinal and transverse reinforcement ratios resulted in significant improvements in the load and moment capacities of GPC columns reinforced with GFRP bars and GFRP helices.

This study aims to experimentally and analytically investigate the effectiveness of non-uniform wrapping on circularised reinforced concrete (RC) columns under axial and flexural loads. Sixteen spe...

Geopolymers are recognised for their environmental benefits and excellent chloride and sulfate resistance. However, information on the material characteristics and bond behaviour of geopolymers based on fly ash (FA) and slag is still relatively scarce. This paper presents a comprehensive study on the integration of two modern construction materials – geopolymer concrete (GPC) based on FA and ground granulated blast-furnace slag and glass-fibre-reinforced polymer (GFRP) bars. The aim of the study was to assist concrete structural design by identifying the key preparation parameters such as hardening and bond behaviour. It was found that the hardening of the GPC was much faster than that of ordinary Portland cement (OPC) concrete at an early age and the stress–strain curves, elastic moduli and splitting tensile strengths of the GPC were accurately predicted by existing models developed for OPC concrete. The GFRP bars in the GPC outperformed those in the OPC concrete in terms of normalised bond strength. The GPC reinforced with both GFRP and steel rebars exhibited similar bond–slip curves to the OPC concrete. Overall, the behaviour of the GFRP-reinforced GPC was found to be analogous to that of the OPC concrete while providing adequate compressive, tensile and bond strength for the construction of foundations of low-rise buildings.

This study discusses the behavior of ambient-cured circular geopolymer concrete specimens tested under different loading conditions. Twelve specimens were cast and tested to investigate th...

This paper presents an experimental investigation into the behavior of Glass Fiber-Reinforced Polymer (GFRP) bar reinforced high strength concrete and ultra-high strength concrete beams. In total, twelve GFRP bar reinforced concrete beams (GFRP-RC beams) were constructed and tested. Six GFRP-RC beams were tested under static loading. Higher strength concrete was found to influence the overall behavior of GFRP-RC beams under static loading in terms of load carrying capacity, deflection, and post-cracking bending stiffness. Six GFRP-RC beams were tested under impact loading at various levels of impact energy. The GFRP-RC beams displayed a shift in the failure mode (from shear failure to flexure failure) as a result of the use of ultra-high strength concrete under impact loading.

The behaviour of Glass Fibre-Reinforced Polymer (GFRP) bar reinforced concrete beams varies significantly from the behaviour of traditional steel bar reinforced concrete beams. This paper numerically investigates the response of GFRP bar reinforced concrete (GFRP-RC) beams under monotonic loads. This paper also presents the details of a three-dimensional Finite Element (FE) model for GFRP-RC beams under monotonic loads. The results of the numerical modelling have been validated against the experimental results of nine GFRP-RC beams. The results of the FE analysis have been found to be in very good agreement with the experimental results. Furthermore, a parametric study is carried out to investigate the effects of the reinforcement ratio, compressive strength of concrete, and shear span to effective depth ratio on the response of GFRP-RC beams. The effects of these parameters on the load-midspan deflection behaviour, energy absorption capacity, and failure modes of GFRP-RC beams have been adequately discussed in this paper.

This study examines the properties of fiber-reinforced reactive powder concrete (FR-RPC). Steel fibers, glass fibers, and steel-glass hybrid fibers were used to prepare the FR-RPC. The non-fibrous reactive powder concrete (NF-RPC) was prepared as a reference mix. The proportion of fibers by volume for all FR-RPC mixes was 1.5%. Steel fibers of 13 mm length and 0.2 mm diameter were used to prepare the steel fiber-reinforced RPC (SFR-RPC). Glass fibers of 13 mm length and 1.3 mm diameter were used to prepare the glass fiber-reinforced RPC (GFR-RPC). The hybrid fiber-reinforced RPC (HFR-RPC) was prepared by mixing 0.9% steel fibers and 0.6% glass fibers. Compressive strength, axial load-axial deformation behavior, modulus of elasticity, indirect tensile strength, and shear strength of the RPC mixes were investigated. The results showed that SFR-RPC achieved higher compressive strength, indirect tensile strength and shear strength than NF-RPC, GFR-RPC, and HFR-RPC. Although the compressive strengths of GFR-RPC and HFR-RPC were slightly lower than the compressive strength of NF-RPC, the shear strengths of GFR-RPC and HFR-RPC were higher than that of NF-RPC.

This paper presents a new strengthening technique for square-reinforced concrete (RC) columns by circularisation with reactive powder concrete (RPC) and wrapping with fibre-reinforced polymer (FRP)...

In this study, a new equation is proposed to compute the maximum axial load carrying capacity of FRP bar reinforced concrete columns under axial compression. The equation proposed in this study was critically compared with the equations proposed in the previous research studies using a wide range of experimental data taken from the available literature. In general, it was found that computing the contribution of the FRP longitudinal bars in concrete columns based on the modulus of elasticity (stiffness) of the FRP bars provides more rational predictions than computing the contribution of the FRP longitudinal bars based on the ultimate tensile strength of the FRP bars. It was also found that using a concrete compressive strength-based empirical equation in estimating the axial strain in the FRP longitudinal bars in concrete columns provides more accurate predictions of the contribution of the longitudinal FRP bars in the axial load sustained by the FRP bar reinforced concrete columns.

This study presents an experimental evaluation of three different methods for determining the tensile strength of steel fibre reinforced concrete (SFRC). The test methods include the splitting test (ST), double punch test (DPT) and direct tensile test (DTT). The compressive strength of the concrete used in this study ranged between 30 and 80 MPa with 0%, 1·5% and 3% steel fibre by volume of the concrete. In total, 81 concrete cylinders were cast and tested for 28-d compressive strength, splitting tensile strength and double punch tensile strength of the concrete. In addition, 27 concrete prism specimens were cast and tested to determine the direct tensile strength of the concrete. The test results show that, compared to the ST, the DPT is more effective in predicting the tensile strength of SFRC, as the tensile strengths obtained from the DPT and the direct tensile test are very close. The DPT is easier to perform and costs less than the ST and the DTT.

Hollow-core concrete columns are widely used as structural members to reduce the cost and self-weight of concrete structures. This study investigates the axial load–axial deformation behav...