Detrimental Effects of Fly Ash Backfill on Retaining Wall Stability and Associated Chemical Reactions

Abstract

Fly ash, a by-product of coal combustion in thermal power plants, has been increasingly used in civil engineering applications, including as a backfill material for retaining walls. While fly ash offers certain economic and environmental benefits, its use can pose significant risks to retaining wall stability.  Fly ash, also recognized as coal fly ash, is a substantial global issue. Pollution manifests as solid waste categorized as "hazardous waste," resulting from the electricity generation process in thermal power plants. Some metals such as Al, Fe, Ca, and Magnesium constitutes over 85% of the chemical compounds and glasses found in the majority. It is consisting a chemical range from 70% to 90% including glasses of iron and alumina. silica and calcium oxide. It is important to mention that, fly ash can serve as a dependable and alternative source of ferrous materials aluminum oxide and silicon dioxide. This paper examines the detrimental effects of fly ash backfill on retaining wall stability, focusing on the geotechnical properties, potential for leaching of toxic elements, and chemical reactions that may compromise structural integrity. A comprehensive analysis of the chemical interactions between fly ash and the retaining wall materials is presented, highlighting the conditions under which these reactions are most likely to occur. The paper concludes with recommendations for mitigating the risks associated with the use of fly ash as a backfill material.