Visual inspection and mechanical testing of fly ash-based fibrous geopolymer composites under freeze-thaw cycles

Abstract

In this research, an experimental study was conducted to evaluate freeze–thaw behaviour of fiber reinforced geopolymer mortars. To build up an extensive experimental program, three different fiber types of basalt fiber (BF), steel fiber (SF), and glass fiber (GF) with two different lengths, three fiber volume fractions of 0.4, 0.8, and 1.2%, and three freeze–thaw cycles of 100, 200, and 300 were chosen as the experimental parameters. Here, the solid binding component was the fly ash with a fixed dosage of 550 kg/m3 while the alkaline activators were Na2SiO3 and NaOH solutions. A fixed alkaline activator-to-binding material (solid binding component) ratio of 0.5 was assigned. In total, 13 different fly ash-based geopolymer mixtures were designed. Based on the results of the experimental program it was found out that the workability of the geopolymer mortars was adversely affected by the fiber addition. A continuous increase in both compressive and flexural strengths was achieved when the volume fraction of the BF and SF type fibers were increased. Another critical finding is that utilization the fiber decreased the damage of the freeze–thaw cycles. Therefore, it was proved that the use of fiber can be an effective way to increase the durability of the geopolymer mortar against the freeze–thaw cycles. The mortars manufactured in this study maintained their integrity even after being subjected to the 300 freeze–thaw cycles. In order to provide a better assessment, the experimental program was supported by visual inspection of the specimens at each 100 freeze–thaw cycles. © 2021 Elsevier Ltd