Abstract:
Incineration, the mostly used medical waste management system now a days, generates substantial amounts of fly ash. Inappropriate disposal of medical waste incineration fly ash (MWIFA) can be hazardous, contaminating the surrounding environment. Compressed stabilized earth block (CSEB) can provide a sustainable way to stabilize such harmful material promoting both pristine material conservation and hazardous waste management.
This study focuses on the suitability of incorporating MWIFA in CSEB preparation through several physical and mechanical tests. For this study, 275 CSEBs are prepared with 0-10% cement and 0-40% MWIFA variation (All the percentages are taken by the dry mass of soil). Characterization of MWIFA reveals the MWIFA as a high lime fly ash, with 63.9% CaO, suitable for cementitious construction. Physical properties of CSEBs have been evaluated through visual inspection and dry unit weight test. Up to 30% addition of MWIFA has been ideal for density and serviceability acceptance.
Strength characteristics have been evaluated in terms of dry compressive and flexures strength tests. Both of these strengths have been increased with up to 30% MWIFA addition for both unstabilized (samples without cement) and stabilized samples. Durability characteristics of CSEBs have been investigated through moisture absorption, wet compressive and flexure strength, wetting drying cycle, and external sulfate attack test. The lowest water absorption values are recorded at 10% cement content, while addition of MWIFA up to 30% has been beneficial for attaining moisture susceptibility. After 24 hours submersion in water, the mechanical strengths of all samples are reduced. The samples with 10% and 20% MWIFA have showed maximum compressive and flexure strengths respectively, while all stabilized samples have showed better flexural durability properties. Wetting drying cycle test results reveal the robustness of the CSEBs due to MWIFA addition up to 40%. The mechanical properties have also been increased due to the cyclic heat and water exposure. The sulfate attack test shows the removal of efflorescence in MWIFA can be achieved through any amount of MWIFA addition up to 40%. But the extended sulfate exposure has been destructive for all samples, implying the influence of other factors like particle size distribution to the CSEB mix.
The short-term leaching behavior of the specified heavy metals (Pb, Cr, Cd, Cu, Ni, and Zn) has been analyzed using the Toxicity Characteristics Leaching Procedure (TCLP). The heavy metal concentrations obtained from the TCLP test results for all CSEBs are far below the USEPA regulatory limits except some samples with 40% MWIFA. The cumulative concentrations of these heavy metals are found far below the Dutch regulatory limit (U1) from NEN 7345 Dutch tank leaching tests. The CSEB sample, which meets all the strength and durability properties and environmental safety limits, is selected as an optimum mix. The results reveal that up to 30% MWIFA can be valorized in CSEBs, creating an opportunity of eco-friendly construction material preparation and sustainable waste management.