Towards Sustainable Masonry Construction Through Natural Aggregate Replacement by Fine Recycled Aggregates in Cement–Lime Mortars

Sustainable development relies on the circularity in the built environment, which, in turn, includes recycling construction and demolition waste and using recycled materials. However, using fine recycled fractions is challenging, especially considering the requirements for new building applications. Yet, producing more widely applied recycled coarse aggregates usually leads to the simultaneous generation of recycled sand fraction, which contains many fines that pose potential problems. This work presents the direct incorporation of concrete and mixed waste-based recycled sand and recycled fines in masonry mortars, on the one hand, as a complete aggregate replacement and, on the other, only replacing the finest aggregate fraction. Such mortars are assessed based on the fresh and hardened mortar properties and are compared to natural aggregate-containing mortars. In the fresh state, the mortars with recycled fines and recycled sand required more mixing water to produce comparable consistency and workability. In a hardened state, mortars with recycled mixed waste sand and fines have demonstrated increased mechanical strength compared to natural aggregate mortars. In contrast, those containing recycled concrete aggregates and fines were inferior in that regard. This indicates the potential of using recycled mixed waste fractions to improve masonry mortar performance, although both types might be important in enhancing the sustainability of masonry construction.