Characterization of pond ash-bentonite mixes as landfill liner material

Abstract

Characterization of pond ash-bentonite mixes is made to assess their suitability as liner material for waste disposal facilities by examining the relevant index and engineering properties. Further, a comparative assessment is made between sand-bentonite and pond ash-bentonite mixes for the range of bentonite content varying from 0 to 30% by weight at an interval of 5% to ensure an effective substitution of sand with pond ash. Addition of bentonite to sand or pond ash significantly influences the plasticity, strength and permeability properties. Besides, the shape parameters of the coarser fraction and morphology of compacted mixes also influence the engineering properties. A multiple linear regression equation is suggested to predict the hydraulic conductivity of these mixes by considering the basic material properties such as liquid limit, plasticity index and void ratio as an input variable with a correlation coefficient of 0.92 between the measured and predicted hydraulic conductivity values. At comparable conditions, compacted pond ash-bentonite mixes exhibit higher strength but also higher permeability than sand-bentonite mixes. Pond ash-bentonite and sand-bentonite mixes met the liner requirements when compacted with modified Proctor compaction effort at a minimum bentonite content of 20% and 15%, respectively.

Structure and Strength of Artificial Soils Containing Monomineral Clay Fractions

“…Soil structure is a unique and important feature governing the development of plants, absorption of nutrients, growth of roots [ 1 ], aeration and water transport [ 2 ], resistance to erosion [ 3 ], and many others features. The strength and durability of soil structure are key factors influencing a number of soil performance characteristics, such as stability of landfill liners, specific barriers for nuclear waste disposal, foundations for buildings, roads and embankments [ 4 , 5 , 6 , 7 ], soil bearing capacity [ 8 , 9 ], settlement [ 10 ], deformation by machines [ 11 ], the velocity of seismic waves [ 12 ] and many others.…”

“…In studies of multicomponent systems of clay minerals, Ye et al [ 25 ] showed that montmorillonite significantly increased the compression of kaolinite-based clayey soils, while contents of illite and chlorite were less influential in these systems. The beneficial effect of bentonite on the hydraulic conductivity, mechanical stability and permeability were indicated in mixtures with sand, pond ash or fly ash [ 5 , 6 , 26 ]. Charkley et al [ 27 ] reported an increase in cohesion and shear strength with an increase in kaolinite/montmorillonite content in artificial clay soil.…”