Mechanical performance and life cycle assessment of alkali-activated concrete with municipal-waste incinerated bottom ash as partial precursor

Municipal waste incinerator bottom ash (MIBA) is gaining attention as a sustainable material for concrete. While its use in mortars has been studied, its impact on the strength and sustainability of alkali-activated concrete (AAC) is still underexplored. Therefore, this study aims to evaluate the potential of MIBA as a partial replacement for fly ash (FA) in AAC. First, MIBA was milled and sieved to match FA particle size, then thoroughly analyzed using advanced techniques. Concrete samples were prepared by replacing FA with 5-20% MIBA by weight. A solution of 12 M sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) in a 1:2 ratio was used as the alkaline activator (AA). The samples were cured at 60 degrees C for 72 h and conditioned at ambient temperature for 28 days. The mechanical performance of MIBA in AAC was assessed through compressive strength, dry density, and SEM analysis, while Life Cycle Assessment (LCA) evaluated environmental impact and sustainability. The results showed that MIBA reduced strength due to its reactivity, with compressive strength dropping from 40 to 25 MPa at 20% replacement. However, up to 5% replacement had minimal impact, with strength only decreasing from 40 to 36 MPa. Even at 15% replacement, strength remained at 29 MPa, which is above the acceptable threshold of 28 MPa. The Life Cycle Assessment (LCA) revealed that MIBA improved sustainability by reducing Terrestrial Acidification Potential (TAP) and Marine Eutrophication Potential (MEP) by 16% at 5% replacement, 45% at 15% replacement, and 60% at 20% replacement. However, its energy-intensive processing increased Global Warming Potential (GWP), which remains an environmental concern.