Optimization of fiber aspect ratio for 90 MPa strain-hardening geopolymer composites (SHGC) with a tensile strain capacity over 7.5%

This study developed high-strength strain-hardening geopolymer composites (SHGC) containing 2% (by volume) polyethylene (PE) fibers. A high-strength geopolymer matrix with a compressive strength of over 100 MPa was achieved using liquid crystal display glass powder and ground granulated blast furnace slag. To determine the optimum aspect ratio of PE fibers, five different types of PE fibers with aspect ratios ranging from 300 to 900 were considered. The average bond strength of PE fibers in the high-strength geopolymer matrix was 1.55 MPa, similar to that of high-strength cement matrices. The PE fibers with higher aspect ratios were more effective for improving the tensile performance of high-strength SHGC than those with lower aspect ratios, and a robust strain-hardening characteristic with saturated micro-crack patterns was obtained when the fiber aspect ratio exceeded 600. The energy-based pseudo strain-hardening index (Jb′/Jtip) was found to be 25.3 at a fiber aspect ratio of 600, and it increased to 104.3 with the increase in the fiber aspect ratio up to 900. The best tensile performance—tensile strength of 5.73 MPa, strain capacity of 7.58%, and strain energy density of 309.6 kJ/m3—was achieved in the high-strength SHGC reinforced with PE fibers having an aspect ratio of 900.