Abstract
The study evaluated the feasibility of using two industrial by-products: municipal solid waste incineration bottom ash (MSWI-BA) and cement kiln bypass dust (CBPD), as partial replacements of conventional constituents in cement mortars. MSWI-BA was used as a replacement for standard sand (5, 10, 15, and 20%, introducing a volumetric adjustment to the weight of the norm sand), while CBPD was used as a replacement for cement (2.5 and 5.0%); both materials were introduced either individually or in combination. The flow of fresh mortars, water absorption and dry bulk density, flexural and compressive strengths at 7 and 28 days, and resistance to freeze - thaw cycling (25 cycles) were investigated. The incorporation of the by-products reduced consistency (from 2.2 to 30.6%) and increased water absorption by 11.1 - 18.5% relative to the reference mix. All modified series showed lower mechanical strength than the reference mortar; among the mixes incorporating a single by-product, the highest 28-day compressive strength was obtained for 5% MSWI-BA (≈44 MPa), whereas the combined mix MIX 5/2.5 reached 37.1 MPa. After freeze - thaw cycling, the modified mortars exhibited lower mass loss (0.07 - 0.36%) than the reference series (0.82%). The results suggest that incorporating MSWI-BA and CBPD at low substitution levels can be a practical step towards more sustainable, circular-economy-oriented mortar production, combining reduced landfilling of waste materials with a lower demand for virgin raw materials.