Compressive Behaviour of Pull-wound GFRP-Confined Concrete Columns Incorporating Glass Powder and Rubber Fibres: Experimental and Theoretical Investigation

: To reduce the carbon footprint of concrete production while enhancing sustainability through circular-economy principles, this study investigates the compressive behaviour of concrete incorporating recycled glass powder (GP) as a partial cement replacement and nitrile rubber (NR) gloves as additive fibres. However, the inclusion of these waste materials, leads to a reduction in compressive strength of concrete, thereby limiting its structural application. To mitigate the strength loss and enhance the ductility and energy absorption capacity, the novel sustainable concrete was confined using pull-wound glass fibre-reinforced polymer (PW-GFRP) tubes. In this study, nine different concrete mixtures were prepared incorporating varying dosage of recycled GP and NR fibres and the compressive behaviour were tested both with and without PW-GFRP confinement. A total of 18 PW-GFRP confined stub columns were prepared, consisting of one circular and one square specimen for each batch of concrete mix. The results showed that the inclusion of GP and NR fibres reduced the compressive strength of unconfined concrete, with a compounded strength loss observed when both materials were combined. For unconfined concrete, strength reductions of up to 55% were recorded. However, this reduction became less pronounced upon PW-GFRP confinement, which achieved a net strength recovery of around 40% relative to the corresponding unconfined specimens. Moreover, the axial performance of this novel sustainable concrete was significantly improved with PW-GFRP tube confinement. The key parameters of the PW-GFRP confined stub columns were discussed, which includes failure mode, load-displacement behaviour, load-strain relationship, strength index, confinement ratio, ductility index and fracture energy. The experimental results of this study were also evaluated against existing theoretical models, and they failed to predict the axial capacity of the PW-GFRP confined columns with reasonable accuracy, Subsequently, a new model was developed which demonstrated considerably improved accuracy and reduced scatter.