Sustainable use of medical waste incineration fly ash in compressed stabilized earth blocks

This study investigates the suitability of incorporating medical waste incineration fly ash (MWIFA) as a partial replacement of cement in Compressed stabilized earth blocks (CSEB). MWIFA is a high-lime fly ash and can promote pozzolanic activities, but its sustainable use in adverse conditions will depend on the durability of the blocks and adequate encapsulation of the toxic metals present in the fly ash. Several strength and durability tests were conducted on 275 CSEB specimens prepared with 0–10 % cement and 0–40 % MWIFA variation. Both dry compressive and flexure strengths increased, and moisture susceptibility decreased with up to 30 % MWIFA addition. Compared to cement-free samples, the improvement of most properties in MWIFA-doped samples is notable, indicating that MWIFA has imparted significant binding properties to the blocks. After 24 h of submersion in water, the blocks retained good compressive and flexure strengths abrasion resistance (AML<5 %), which shows that MWIFA can enhance the durability of CSEBs. MWIFA incorporation resulted in the removal of efflorescence, although extended sulfate exposure had a deleterious effect on all samples. Particle size distribution of the MWIFA and localized ettringite crystal formation on the CSEB mix, as evidenced through microstructural observation, could be responsible for such effects. Experiments indicate that a maximum of 30 % replacement of cement with MWIFA can be prescribed without compromising the quality of the block. The short-term and long-term leaching tests for six heavy metals (Pb, Cd, Cr, Cu, Ni, Zn) confirmed that there is minimal concern for environmental hazards of using MWIFA in CSEBs. MWIFA utilization in CSEB is a viable option for enhancing its durability and strength, as well as an attractive measure for sustainable waste management.