Constitutive model of polypropylene-fiber-fabric-reinforced concrete under uniaxial compression and index conversion of mechanical properties

Polypropylene fiber (PPF) is often added to improve the mechanical properties of concrete in engineering applications. As a material used extensively in the textile industry, a huge amount of discarded polypropylene fabrics (PPFF) are produced each year. This study used the waste PPFF as the research object to investigate the feasibility of replacing PPF as concrete admixture on the basis of the concept of green environmental protection. The mechanical properties of polypropylene fiber fabric-reinforced concrete (PPFFRC) with five different fabric contents of 0–1.5 kg/m3 under three different curing ages of 14–60 days were tested. Results show that the dosage of 0.9 kg/m3 PPFF is the best. Compared with the polypropylene fiber reinforced concrete with the same dosage at the age of 60 days, the compressive strength increased from 35.83 MPa to 42.83 MPa, the flexural strength increased from 5.99 MPa to 6.344 MPa, and the splitting strength decreased slightly from 2.70 MPa to 2.57 MPa. A uniaxial compression constitutive model of PPFFRC with different fabric contents at different curing ages was established on the basis of the uniaxial compression constitutive model of concrete proposed by Hogenestand and Zhenhai Guo. The correlation coefficient in the constitutive model was determined by using an improved differential evolution algorithm. The conversion relationships between compressive-flexural strength, compressive-splitting strength, and compressive strength-elastic modulus of PPFFRC were constructed. Results show that the waste PPFF has broad application prospect in green concrete and can replace PPF in concrete to some extent.