Effect of basalt fiber on fracture properties and drying shrinkage of alkali-activated slag with different silicate modulus

This study investigated the impact of basalt fiber on the microstructure, compressive strength, fracture properties, and drying shrinkage of alkali-activated slag (AAS) with varying silicate modulus (Ms) of activators. The AAS samples were characterized by using the SEM-EDS, FTIR, and TGA tests. The results showed that the corrosion behavior of basalt fiber differed in the alkaline solution depending on the Ms of the activator. When the Ms is 0, a brittle shell-like gel layer tended to form on the surface of the basalt fiber, resulting in the weak bonding between the basalt fiber and AAS matrix and limiting the reinforcing effect of basalt fiber. The mechanical and fracture properties can be effectively improved when the Ms of AAS was above 1, as the tight bonding between the basalt fiber and the AAS matrix enhanced the bridging effect of the basalt fiber. Additionally. the structure of the C-A-S-H in AAS can be improved with the added basalt fiber, especially with high Ms, which further facilitated the enhancement of the mechanical and fracture properties of AAS. Moreover, the effectiveness of basalt fiber in reducing the drying shrinkage of AAS was enhanced with increasing Ms.