Utilisation of Clinical Waste Incineration Fly Ash and Silica Fume as Supplementary Cementitious Materials in Mortar: Performance Evaluation and Environmental Impact Assessment

Abstract

The rising production of Clinical Waste Incineration Fly Ash (CWIFA) presents disposal challenges due to high costs, limited land availability, and pollution concerns. However, using CWIFA as a supplementary cementitious material in mortar could help reduce the reliance on Portland cement in construction. Before adopting this approach, it is essential to ensure that CWIFA is adequately solidified and stabilized in the mortar to prevent the leaching of harmful heavy metals into the environment. This study explores the use of CWIFA and silica fume (SF) as supplementary cementitious materials in mortar. Two series of samples were tested: Series 1 and Series 2, incorporating varying percentages of CWIFA (0%, 2.5%, 5%, 10%, and 15%) and SF (0% and 10%), with a constant fine aggregate-to-cementitious ratio of 2.75 by mass and constant water-to-cementitious ratio of 0.485. This study investigated the effect of adding CWIFA and SF on mortar’s strength properties. Additionally, the study found that a combination of Portland cement and 10% SF effectively enhances physical encapsulation and minimizes heavy metal leaching (nickel, arsenic, chromium, lead, and selenium) as determined by the Toxicity Characteristic Leaching Procedure (TCLP USEPA Method 1311). These findings suggest that incorporating CWIFA and SF can improve the strength performance of mortar mixtures and offer potential benefits for construction and environmental remediation.