Bentonite: Kaolinite clay liner

Abstract

Conventional geosynthetic clay liners (GCLs) contain bentonite. Since high-quality bentonite is not easily available in Southeast Asia in comparison to kaolinite, an alternative cost-effective method is necessary. The concept of creating a GCL with a bentonite and kaolinite mixture on a biodegradable jute base is discussed in the present paper. The hydraulic conductivity and consolidation behaviour of bentonite: kaolinite mixtures was investigated. It was revealed that at least 30% bentonite was required in the mixture to result in the same decreasing coefficient of consolidation trend with pressure as shown using pure bentonite. The 50:50 bentonite:kaolinite (50:50 B:K) ratio yielded approximately the same hydraulic conductivity, k, as pure bentonite; hence, the remainder of the study focused on the 50:50 B:K mixture. For the 50:50 B:K mixture hydraulic conductivity measurements, the following permeants were used: (i) distilled water, (ii) 0.25M calcium chloride, (iii) 0.1M hydrochloric acid, and (iv) 0.1M sodium hydroxide. With the calcium chloride permeant, the hydraulic conductivity of the mixture was found to be in the range of 10-10 m/s, whereas the hydrochloric acid and sodium hydroxide permeants yielded values near 10-11 m/s. It was also found that the liquid limit and swell index tests carried out on bentonite and the B:K mixture were significantly affected by the presence of a large amount of calcium chloride. A jute-based clay liner was then created with the 50:50 B:K mixture. Its effectiveness in the landfill liner system was investigated for equivalency and was found to be satisfactory when using distilled water as the permeant. The biodegradability of jute and the effect of organic chemicals on the clays are beyond the scope of the present paper.