Effect of alkali-resistant glass fiber and silica fume on mechanical and shrinkage properties of cement-based mortars

Abstract

Fiber-reinforced concrete is widely applied owing to its significant mechanical properties and great resistance to cracking. However, the alkaline environment of pore solutions adversely affects the fibers, which reduces the concrete strength and durability. Considering this, alkali – resistant (AR) glass fiber (GF) materials, including both GF and glass fiber powders (GFP), were used to improve the condition. Furthermore, the co-efficient of AR-GF and silica fume (SF) was studied. For each material, three replacement levels were designed, and 10 groups of specimens were cast in this experiment. The compressive strength, flexural strength, autogenous shrinkage, and drying shrinkage of mortars were measured, at the same time, microstructure of some presentive samples was observed through scanning electron microscopy (SEM) tests. The experimental results showed that GF has a great effectiveness on enhancing the mechanical properties of mortars, especially to flexural strength, for which 57% improvement was observed under 28d curing when 7.5% GF was added. Meanwhile, AR-GFP showed the extrordinary effect on mitigating the mortars’ shrinkage. 40% autogenous shrinkage and 50% drying shrinkage were eliminated when 5% GFP was incorporated in mortars. However, the effectiveness was reduced with continuous increase of GFP. Unsurprisingly, the mechanical properties of mortars with GF was further improved when SF was added into mortar, in which additional 50% enhancement of flexural strength and 10% enhancement of compressive strength were achieved. However, SF refined the pore size of mortars which resulted in the increase of autogenous shrinkage and drying shrinkage. In a short, The use of AR fiber materials and SF improved the mortars’ mechanical properties and durability, which has a high practical value.