Utilization of Fly Ash-Bentonite Mixture as an Alternate Liner Material

Abstract

A landfill liner should be a low permeable barrier which prevents a pollutant in a waste containment system from entering surface water, ground water and thus polluting them. The performance of the lining system is greatly affected by its hydraulic conductivity (Daniel 1987, 1990). Highly expansive clays such as bentonites (because of their low hydraulic conductivity, k ≤ 10-9 m/sec) mixed with certain geo-materials are used for the construction of hydraulic barriers. Bentonites consist of montmorillonite minerals; they are highly plastic in nature. Though bentonites are low permeable, they exhibit very low strength and very high volume change with variations in water content which is not acceptable in the case of hydraulic barriers.Compacted sand-bentonite mixtures are widely used as a liner material in municipal and hazardous waste containment (Akgun et al, 2015; Al-Rawas et al, 2006). In spite of its low hydraulic conductivity, the usage of sand-bentonite mixtures as liner material is decreasing now-a-days due to the non-availability of sand and growing environmental concerns related to its dredging. Therefore, there is an urgent need to find some alternate material for the construction of liners. This forms the scope to explore the usage of waste material like fly ash as an alternate liner material to sand. In this present work, the geotechnical investigation has been carried out to study the hydraulic conductivity, unconfined compressive strength, plasticity, and swelling characteristics of fly ash bentonite mixtures with bentonite content 5, 10 and 15 percent by dry weight respectively and suggested suitable fly ash bentonite mix considering the above criteria.