Experimental study on cyclic flexural behaviour of GFRP-reinforced seawater sea-sand concrete slabs with synthetic fibres

Seawater and sea-sand (SWSS) concrete is a new type of concrete with many economic and environmental benefits. However, chloride-induced corrosion of steel reinforcement is a major problem associated with this type of concrete. Due to its excellent resistance in chloride environments glass fibre reinforced polymer (GFRP) reinforcement could be utilized in SWSS concrete as an alternative to steel Adding fibres can also improve the concrete properties reinforced with GFRP bars. Fibres can affect the post-crack response and failure mode of GFRP reinforced concrete and also improve the bond between rebar and concrete. This study focused on the flexural behaviour of GFRP reinforced SWSS concrete slabs with or without fibre incorporation which has not yet been fully addressed in the literature. Polypropylene (PP) and polyvinyl alcohol (PVA) fibres were used for the concrete reinforcement. Under-reinforced (p < pb) and over-reinforced (p > pb) GFRP reinforced concrete (RC) slabs were prepared and subjected to four-point cyclic bending loads. The results show that GFRP bar is a promising alternative to steel for SWSS concrete reinforcement. The GFRP RC slabs with plain SWSS concrete had a cracking moment which was 13% lower than the values predicted by the ACI 440.1R-15 provisions. However, adding fibres, particularly PP fibres, could successfully compensate for this reduction. Variation in GFRP rein- forcement ratio had almost no effect on cracking moment. With the addition of fibres, the cracking moment and ultimate strength of the slabs were both improved. Crack width and crack spacing were reduced in fibre - reinforced SWSS concrete slabs compared with the plain concrete counterparts. Fibres reduced the residual deflection of the slabs at the end of each cycle. Comparing experimental deflection results with the values predicted by different models revealed that there is no available model could satisfactorily predict deflection for all the GFRP reinforced SWSS slabs.