Experimental and theoretical investigation on axial compression of seawater sea sand rubberised concrete filled pultruded GFRP tubes

This paper presents an experimental and theoretical investigation of seawater sea sand rubberised concrete (SWSSRuC) filled pultruded glass fibre-reinforced polymer tubes made with the pullwinding technique (P-GFRP). Mix proportions for the novel sustainable SWSSRuC were initially developed to attain the desired mechanical properties. P-GFRP tubes were utilized to mitigate the loss in mechanical properties of SWSSRuC caused by the presence of rubber. The parameters investigated were the cross-sectional shape of the P-GFRP tube, the strength of the infill concrete, and the rubber replacement level. A total of 14 specimens, including 12 confined specimens and 2 hollow tubes, were tested under axial compression. The effects of the key parameters on the failure mode, load-displacement relationship, load-strain behaviour, fracture energy, and axial stiffness are discussed. The results show that the axial compressive performance of SWSSRuC can be enhanced using the P-GFRP tube, and this enhancement improves with increasing rubber content, decreasing infill concrete strength, and when the shape of the tube is circular. Furthermore, the composite action significantly improved the buckling sensitivity and axial stiffness of hollow P-GFRP tubes. In the end, modifications to existing models are proposed to predict the axial capacity of SWSSRuC filled circular and square cross-sectioned P-GFRP tubes. • Developed mix design of novel seawater sea sand rubberised concrete (SWSSRuC) • Employed pultruded GFRP (P-GFRP) tubes to restore mechanical properties of SWSSRuC • Utilised P-GFRP tubes had fibres oriented in both axial and transverse directions • Studied key parameters affecting axial performance of SWSSRuC filled P-GFRP tubes • Proposed equations accurately predict the capacity of SWSSRuC filled P-GFRP tubes