Effect of low dosages of waste GRP dust on fresh and hardened properties of mortars: Part 2

Part 1 of the work reported that by replacing 5–10% of sand volume with GRP dust, workability, autogeneous shrinkage, deformability and total porosity, though with a smaller average radius, of mortars increased, thereby reducing significantly the mechanical performance, when wet curing conditions are adopted. However, the risk of cracking induced by restrained shrinkage and the capillary water absorption is lower in the presence of GRP dust, leading to enhanced durability of GRP mortars when used as supporting role. Therefore, in the present work, plaster mortars manufactured by replacing 0–2.5–5% of sand volume with GRP dust were characterized. For comparison, the addition of an hydrophobic admixture at different dosages was also considered. Permeability is not significantly reduced by the low addition of GRP dust, but it is slightly increased by silane addition. Thermal insulation properties, capillary water absorption and resistance to efflorescence are better with waste GRP dust addition, especially when combined with silane.