Mechanical and fracture properties of fly ash-based geopolymer concrete with different fibers

The harm of cement has become a global concern due to its high energy consumption, environmental impact, and human health risks that come from continuous cement production. The development of fly ash-based geopolymer concrete (FGPC) was considered an effective and sustainable solution. However, FGPC is much more brittle than ordinary concrete, which needs to be solved urgently. Thus, the effects of three different fiber types, namely basalt fiber (BF), polyethylene polypropylene fiber (PF), and steel fiber (SF), on the mechanical properties and fracture toughness of FGPC were discussed in this study. The FGPC composites were designed and manufactured with fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.5%, 2.0% for each of the above fibers. Multiple items mechanical tests on cylindrical and notched prism specimens were conducted. In addition, the interfacial bond property between fiber and geopolymer matrix was evaluated by SEM and single-fiber pull-out tests (FPT). The results show that fiber type, fiber volume fraction and fiber-matrix interface properties contribute greatly to the mechanical properties and fracture behavior of FGPC members, thus improving the mechanical property and fracture toughness of FGPC. SEM and FPT analyses support these results. In addition, an energy dissipation model is proposed to consider the fracture process of the FGPC composites in more detail. Based on these studies, the improvement to the brittle behavior of GPC would be achievable.