An experimental investigation on freeze-thaw resistance of fiber-reinforced red mud-slag based geopolymer

This study aims to investigate the influence of different fiber types, lengths, and contents on their performance in freeze-thaw environments. Indoor freeze-thaw tests were conducted to evaluate the flexural strength, compressive strength, and mass loss of fiber-reinforced geopolymer materials. Additionally, SEM and XRD analyses were performed to examine the internal structure of the geopolymer composites. The results demonstrated that the incorporation of different fibers significantly improved various properties, particularly the flexural strength of the specimens. With an increasing number of freeze-thaw cycles, surface cracks became more prominent in the geopolymer specimens, leading to a gradual decrease in frost resistance. However, the addition of an appropriate amount of fiber effectively enhanced frost resistance. Following freeze-thaw exposure, an increase in fiber content initially resulted in a decrease and subsequently an increase in relative flexural strength, compressive strength, and mass loss. Notably, studies revealed that polypropylene fibers with a length of 9 mm and a content of 0.9 % exhibited minimal mass and strength loss. SEM analysis indicated uniform distribution of fibers within the geopolymer matrix, contributing to improved flexural strength and enhanced frost resistance in fiber-reinforced structures. XRD results indicate that red mud-slag based geopolymers produce high-strength hydrated calcium (aluminosilicate) silicate and hematite phases, which enhances the mechanical properties and durability of the specimens. In conclusion, this study highlights that incorporating suitable fibers can enhance the durability and performance of red mud-slag based geopolymers under freeze-thaw conditions. The findings provide valuable insights for optimizing fiber type, length, and content to achieve superior mechanical properties and frost resistance in geopolymer composites.