A cost-efficient UHPC incorporated with coarse aggregates and macro fibres recycled from waste GFRP

High production cost is a key impediment to the broader applications of UHPC materials. In the present study, a concept has been therefore proposed on jointly incorporating coarse aggregates and macro fibres recycled from waste GFRP in the UHPC system to produce a cost-efficient UHPC. The coarse aggregates were respectively incorporated into UHPC using the modified Andreasen and Andreasen model (MAAM) leading to the cement added in per m³ UHPC being as low as 668 kg. Compression and flexural tests were first carried out to examine the effects of incorporating both coarse aggregates and macro fibres on the properties of such a UHPC. The tensile stress-strain curves were then obtained from the data results of bending tests through a twice inverse analysis. A cost analysis was performed as well to quantitatively compare the production costs of different UHPCs, justifying the proposed concept. The test results and discussion revealed that the UHPC incorporated coarse aggregates have a compressive strength of about 150 MPa, and the presence of macro fibres of 6% in volume results in about 20% decrease in the compressive strength of UHPC, but significantly enhances the flexural properties of UHPC, including peak strength, residual strength, and toughness. The production cost of the UHPC mixture has been lowered to about 1700 CNY/m³ by jointly incorporating coarse aggregates and macro fibres. The maximum value of the efficiency index (E) is achieved when utilizing aggregate with a maximum particle size of 9.5 mm and 6% macro fibre.