Optimizing ecological ultra-high performance concrete prepared with incineration bottom ash: Utilization of Al2O3 micro powder for improved mechanical properties and durability

Within the domain of municipal solid waste (MSW) management, incineration is recognized as an efficient volume reduction method, yet it produces substantial quantities of bottom ash (IBA). Redirecting IBA into cementitious frameworks is challenging due to diminished workability, mechanical properties, and durability. This study investigates alumina micro powder (ALMP)'s effect on improving the mechanical and durability aspects of ecological ultra-high performance concrete (EUHPC) produced with IBA. The research examines ALMP's role at various doping levels on the EUHPC's rheological properties, mechanical strengths, durability indices, ultrasonic pulse velocity (UPV), and elastic modulus. Additionally, nanoindentation tests discern ALMP's reinforcing effect on EUHPC's stiffness. Summarizing key findings: ALMP significantly enhances EUHPC's flexural and compressive strengths, with increases ranging from 6.98 % to 24.87 % and 12.39–20.81 %, respectively. Moreover, ALMP raises the elastic modulus by 6.05–19.07% and UPV by 3.11–7.18 %, reflecting a denser, more compact matrix structure. Durability enhancements are evidenced by reductions in drying shrinkage by 4.41–20.01 % and decreased chloride migration by 7.01–22.14 %. Nanoindentation reveals a densification in the microstructure, with escalated high-density C-S-H phases and reduced low-density C-S-H and unhydrated materials. IBA replacement yields energy savings of 11.43 %, CO2 emission reduction of 7.01 %, and cost savings of 1.18 %. The optimal ALMP inclusion is identified at 10 %, balancing workability, mechanical and microstructural benefits in EUHPC. These revelations position IBA as a useful component in the concrete sector and advocate for ALMP as a beneficial adjunct to elevate the performance of IBA-based concrete towards sustainable development goals.