Effects of Fly Ash and Bentonite on Mechanical and Durability Properties of Fiber Reinforced Geopolymer

Being a widely used building material in marine structure, concrete is susceptible to freeze–thaw (F–T) damage in high-latitude marine conditions, which can easily affect the safety and the lifetime of marine infrastructures. This paper investigates the mechanical properties and frost durability of polyvinyl alcohol (PVA) fiber-reinforced geopolymer composites (PFRGC) with bentonite and fly ash before and after frost damage. The mechanical properties of PFRGC were revealed through cubic compressive, flexural and axial compressive strength. The frost durability of PFRGC was also studied through the relative dynamic modulus of elasticity (RDEM). Furthermore, the acoustic emission (AE) technique was adopted to provide real-time monitoring of the damage progress. Meanwhile, the microstructure was characterized by SEM to illustrate the mechanism of macroscopic property degradation. The results show that the compressive strength continued to decrease with increasing fly ash (FA) incorporation when the bentonite admixture was 0%, while the compressive strength of the concrete reached a maximum when FA/C was 1.8 at higher bentonite admixtures (3% and 6%). At the same time, the mechanical and physical performance of PFRGC decreased with freeze–thaw cycles. The AE characteristics were tightly correlated with the progress of damage and stress–strain curves.