Utilization of Recycled Brick Aggregate in Cementitious Composites: Mechanical Performance, Cement Matrix Solidification Effect and Life Cycle Assessment.

The growing production of construction and demolition waste has been stimulating the need to look for sustainable alternatives to natural aggregate used in the production of cement composites. This study evaluates the potential use of recycled brick material as a substitute for natural coarse aggregate in terms of environmental safety, mechanical properties, the solidification effect of the cement matrix, and life cycle assessment (LCA). Recycled brick materials sourced from four recycling yards were characterized using physical, chemical, and leaching tests. Cement composites containing 50%, 70%, 80%, and 100% replacement of natural coarse aggregate with recycled brick material were subsequently designed. The results demonstrated significant variability in the environmental properties of the recycled materials depending on their origin. Compressive strength after 28 days ranged from 31.8 to 36.2 MPa, and all mixtures met the requirements for strength classes C20/25 to C25/30 according to ČSN EN 206+A2. At the same time, a significant solidification effect of the cement matrix was confirmed, leading to a reduction in the concentrations of dissolved substances by 68.0-80.1% and sulfates by 97.8-99.2% compared to the original recycled material. A life-cycle assessment demonstrated a gradual reduction in the environmental impacts as the proportion of recycled brick material increased, with the best results achieved by a mixture with 100% replacement of natural aggregate. The results confirm that recycled brick material can be safely used as a full-fledged substitute for natural coarse aggregate while maintaining the required mechanical properties and reducing environmental impacts.