Effects of two admixtures on the axial compression of concrete-filled fibreglass tubes

Abstract

This paper reports on an investigation into the influence of an expansive admixture (EA) and fly ash (FA) on the axial compressive behaviour of concrete-filled glass-fibre-reinforced polymer (GFRP) tube columns. The effect of EA and FA on the compressive strength and restrained expansion ratio was studied for two concrete strength grades, and optimised mixtures of expansive FA concrete were selected. It was found that the desired concrete strength and maximum expansion was obtained with 12% substitution of EA and 10% substitution of FA. For this study, 12 concrete-filled GFRP tube columns of circular cross-section were designed and fabricated considering parameters including the GFRP tube thickness, EA content, FA dosage and concrete strength. Their axial compressive behaviour was investigated through their failure modes, load-carrying capacity, ultimate stress and stress–strain curves. The results showed that increases in the thickness of the GFRP tube and EA content can enhance the axial compressive strength of concrete-filled GFRP tube columns. The theoretical ultimate load results showed good agreement with the experimental data.