A study on properties of masonry mortar containing recycled fine aggregate

In this paper, the fresh and hardened properties of mortars containing different percentages of recycled sand made from crushed concrete blocks were studied. For this purpose, natural sand was substituted with recycled sand in 0, 25, 50, 75, and 100 percentages. The same particle size distribution for both natural and recycled materials was used. Also, the water to cement ratio was considered 0.55, and the cement to sand weight ratio was considered to be 1:3. Physical properties including water absorption, water permeability, and bulk density of fresh and hardened mortar, and mechanical properties including compressive and bending strength, resistance against freezing and thawing cycles, and drying shrinkage were examined. The experimental results suggest that mortars made with recycled sand had acceptable compressive strengths all above 10 MPa. By increasing the substitution ratio, the workability and workable time of mortars were reduced. Masonry mortar made with recycled fine aggregate had acceptable resistance against freezing and thawing cycles according to ASTM C666. Results of the drying shrinkage test showed that masonry mortar made with recycled sand had more drying shrinkage than mortars made with natural sand which is a result of a more hardened cement volume ratio in the samples containing recycled sand.Overall, it can be concluded that up to 50% replacement level of aggregate can have reasonable mechanical and durability properties and may be suitable for sustainable development.