Compressive behaviour of GFRP-confined geopolymeric recycled aggregate concrete: Effects of RA content, GRAC size and confinement ratio

Substituting geopolymeric recycled aggregate concrete (GRAC) for normal concrete (NC) to fill glass fibre-reinforced polymer (GFRP) tubes and produce green high-performance compression members is a promising construction technology. Although extensive research has been conducted on the performance of GFRP tubes filled with NC in the past decade, gaps in knowledge make it difficult to predict the mechanical behaviour of this new composite member. This paper presents an experimental and analytical study on the progressive failure of GFRP-confined GRAC under compressive loads. A comprehensive investigation was conducted on the effects of the confinement ratio, recycled aggregate (RA) content, and tube size on the compressive behaviour of GFRP-confined GRAC. The test results were compared with those from available studies on confined NC specimens with or without RA. This paper found that GFRP tube confinement had an advantage in alleviating the negative impact of RA on GRAC. The RA replacement ratio and cylindric dimension had no influence on the linear relationship between the confinement ratio and strength enhancement ratio. Predictive models considering the effect of RA content and GRAC size were proposed for the compressive strength and ultimate strain of GFRP-confined GRAC. Finally, a recalibrated stress–strain model was developed to describe the compressive behaviour of GFRP-confined geopolymeric concrete.