Fresh, Mechanical, and Microstructural Properties of Sustainable Mortars Made of Two Recycled Sands from Construction and Demolition Wastes

Abstract

This paper analyses the ability of two recycled sands (RSs) from concrete (CON) and masonry (MAS) wastes for the manufacture of mortars for the construction industry. Manufactured sand (MS) was substituted by both RSs at the rates of 25%, 50%, 75%, and 100%. CON combinations did not demonstrate any correlation between workability and the MS replacement ratio, whereas MAS combinations exhibited a direct relationship between these factors. A decrease in the starting and final setting times was observed for both RS combinations and, in general, longer total setting times. CON combinations showed mechanical strength increases for substitution rates between 25% and 50%, whereas MAS reached improved mechanical strength at 25%. Scanning electron microscopy-energy dispersive X-ray (SEM-EDX)-demonstrated tests allowed for mortar microstructure differences and hydration product formation. Thermogravimetric analysis/derivative thermogravimetry (TG/DTG) tests showed hydrated cementitious compounds’ formation differences and the consumption of Portlandite between combinations and their evolution during curing.