Ultra-high performance concrete reinforced with macro fibres recycled from waste GFRP composites

Ultra-high-performance concrete (UHPC) is a promising cementitious composite to produce lightweight and high-performance structures. Steel fibres are an essential constituting material of UHPC to prevent the brittle failure of UHPC, but the high cost steel fibres impedes the wider application of UHPC to some extent. This paper proposes a concept to produce UHPC reinforced with macro fibres processed from waste glass-fibre-reinforced polymer (GFRP) composites, therefore addressing two issues of the high cost of UHPC as well as the difficulty in disposal of waste GFRP simultaneously. A series of tests have been carried out to investigate the effect of adding macro fibres on the properties of UHPC. The test results show that the incorporation of macro fibres leads to a loss of the workability and a reduction of up to 21.8 % in the compressive strength, but improves the flexural strength and flexural toughness greatly by up to 27.9 % and 46.9 times, respectively. The tensile constitutive relationship has been converted from the results of the bending tests through inverse analyses. The proposed concept of producing UHPC with recycled macro fibres contributes to lowering the price of UHPC, whose properties are comparable to that of UHPC with steel fibres, and establishing an effective routine to valorise the waste GFRP.