Physical-mechanical assessment to mortars including recycled concrete powder and metakaolin

This study aims to evaluate the mechanical and physical properties of mortars incorporating recycled concrete powder (RCP) and metakaolin (MK), a widely utilized supplementary cementitious material (SCM). The mortars were partially replaced with 30 % of either MK or RCP sourced from three distinct sources: construction, demolition, and laboratory. Various parameters, including workability, compressive strength, splitting tensile strength, elastic modulus, water absorption, capillary water absorption, density, void index, and microstructural characteristics of the mortar, were assessed. The findings indicate that the workability of mortars generally decreased due to the morphology and specific surface area of the particle mixtures of RCP and MK. The incorporation of RCP negatively affected the mechanical properties of the mortar. Conversely, mixtures of MK and RCP were observed to maintain or even enhance the mechanical properties of the mortars across all evaluated time intervals (7, 28, and 91 days). In terms of physical properties, the combination of RCP and MK generally led to a reduction in water absorption and capillary water absorption, as well as a decrease in density and void index. Additionally, the use of MK in combination with RCP resulted in a reduction in the amount of cement required (kg·m −3 ·MPa −1 ) compared to the reference mix, demonstrating that this alternative approach is not only technically viable but also sustainable.