Characterization of Mortars Incorporating Concrete Washing Fines: Impact on Mechanical Properties, Microstructure and Carbon Footprint

Abstract

This study examines the potential use of wash fines, a waste product from concrete plant cleaning, as supplementary cementing materials (SCMs) in mortars. The main objective is to assess the feasibility and benefits of this incorporation in terms of technical performance and environmental impact. Extensive tests were carried out on different mortar formulations, incorporating varying rates of washing fines (0%, 10%, 20%, 30%) as a partial replacement for cement. This choice of replacement is prompted by the fineness of washing fine particles. The properties studied included compressive and flexural strength, porosity, density, water absorption, shrinkage and fire resistance. The results show that the incorporation of washing fines increases porosity and decreases mortar density. There was also a decrease in mechanical strength and fire resistance as the substitution rate increased. However, the use of washing fines enables a significant reduction in the mortar’s carbon footprint, reaching up to 29% for the formulation with 30% substitution. This study demonstrates the potential of washing fines as an alternative SCM, as part of a circular economy approach to reducing the environmental impact of the concrete industry. However, it underlines the need to optimize formulations to maintain acceptable technical performance.