Improving dispersion of recycled GFRP fiber in cement mortar with sodium hexametaphosphate

Abstract

The dispersion of recycled glass fiber reinforced plastic (rGFRP) fibers in cement mortars has a significant impact on both the workability and mechanical properties of the composites. In this study, the dispersity of three types of rGFRP fibers was improved in two methods: Method 1: the dispersant (Sodium Hexametaphosphate, SHMP) was directly added into the mortar, and Method 2: the rGFRP fibers were pre-dispersed by the SHMP solution and then added into the mortar. The effect of the two fiber-dispersion methods on workability, mechanical properties, and microstructure of the rGFRP fiber reinforced mortars were investigated by Zeta potential test, mechanical tests, Mercury intrusion porosimetry and X-ray micro-CT analysis. The results showed that Method 2 had more significant improvement in mechanical strength than Method 1 for all types of rGFRP fiber reinforced mortar. The flexural strength of the mortars increased by 58.3%, 43.2% and 105.4% with 7.5 wt% GF1, GF2 and GF3 treated by Method 2, respectively, compared to their untreated counterparts. The pre-dispersion of the fibers with SHMP facilitated better dispersion of the large rGFRP fiber clusters in the mortar by increasing the surface charge of the fibers and enhancing repulsion between them, thus improving the mechanical performance of the mortar. The results of this study will promote the utilization of rGFRP fiber in construction materials.