Technical Properties and Sustainable Reuse of Recycled Excavation Materials as Natural Sand Replacement in Cement Mortar

This study investigates the feasibility of using recycled sand derived from excavation waste as a sustainable alternative to natural sand in mortar production. The novelty of this work lies in the comprehensive evaluation of mortar performance using 100% recycled sand across a wide range of sand-to-cement (S/C) ratios, combined with microstructural and economic analyses. Six mortar mixes with S/C ratios ranging from 0.50 to 2.75 were prepared at a constant water-to-cement ratio. The experimental program assessed fresh and hardened properties, including flow, density, water absorption, compressive strength, and microstructural characteristics. The results demonstrate that excavation waste sand possesses suitable properties for mortar applications. An optimal mix with an S/C ratio of 0.7 achieved superior performance, with a 28-day compressive strength of 48.8 MPa, a density of 2.147 g/cm3, and a flow value of 108%, satisfying both strength and workability requirements. Increasing the S/C ratio resulted in reduced strength and increased water absorption, indicating a clear performance trend governed by paste content and porosity. Furthermore, the study provides practical insights into material efficiency and cost implications, showing that recycled sand mortar can reduce material costs by approximately USD 2.4 per ton compared to natural sand mortar. Overall, the findings support the potential of excavation waste sand as a viable and sustainable construction material, contributing to resource conservation and circular economy practices in the construction industry.