Effect of high-calcium basalt fiber on the workability, mechanical properties and microstructure of slag-fly ash geopolymer grouting material

Abstract In this study, the workability, mechanical properties and microstructure of geopolymer grouting material (GGM) containing high-calcium basalt fiber (HCBF) have been investigated. Basalt fibers with different lengths were selected as the reinforcement and added various contents into geopolymer prepared by slag and fly ash. The setting times, compressive and flexural strengths and water resistance were used to evaluate the workability and mechanical properties of geopolymer. The development of microstructure was characterized by SEM and MIP techniques. Results show that the initial and final setting times, compressive and flexural strengths are increased with the content of HCBF, while the fluidity and drying shrinkage is reduced. On the basis of SEM and MIP tests, the incorporation of HCBF promoted the densification and refined the pore, and consequently reducing the porosity of geopolymer. Generally, the comprehensive performances of geopolymer grouting material mixed with 6 mm HCBF were better than that mixed with 3 mm at the same dosage. Through the analysis, the addition of calcium-high basalt fiber led to the development of C-S-H and C-A-S-H and combined with N-A-S-H or hybrid C(N)-A-S-H gel system, which further enhanced the performance of geopolymer grouting material.