Enhancement of the Mechanical Characteristics of a Green Mortar Under Extreme Conditions: Experimental Study and Optimization Analysis

Household and similar wastes are increasingly being produced in public landfills. Their decomposition requires very high energy consumption, releasing harmful carbon dioxide gases that pollute the air. Therefore, it is necessary to take effective measures to ensure their disposal in an environmentally sustainable and economically feasible manner. Incorporating different types of them into cement matrices can be a valuable solution. To achieve this, physical and mechanical characterization and even subjecting them to harsh conditions of use are a crucial step for their use. Such gaps include this study, which aims to characterize the mechanical properties of two types of slurry containing ground coffee waste, using two types of sand: dune and quarry sand. The research is based on how these slurries perform under extreme conditions such as wetting/drying, freezing/thawing, chloride exposure, and temperature changes. Therefore, the mixtures were manufactured by replacing sand with ground coffee in varying proportions (5%, 10%, 15%, and 20%). Mechanical properties were evaluated after seven cycles of each condition. The incorporation of ground coffee significantly affected the physical and mechanical properties of the slurry, especially after extreme conditions cycles. Using analysis of variance (ANOVA), the effect of substituting ground coffee on the slurry under freeze/thaw conditions was evaluated. Response surface methodology and central composite design models indicated significant results for all alternatives with p values less than 5%. Numerical optimization showed that replacing 20% of sand with coffee powder resulted in the best mixture, demonstrating very satisfactory mechanical performance even at freezing temperatures as low as − 4 °C.