Selection of sand gradations and proportions for sand-bentonite mixtures of fine-grained soil

Abstract

Sand-bentonite mixtures are greatly used as a liner material for covering the waste disposal sites. Naturally available sand contains the altered proportions of fine, medium and coarse sand therefore, the selection of sand gradations and proportions with bentonite is a challenging assignment for any highway material engineers. Additionally, compacted sand-bentonite mixtures used for liner must have higher maximum dry density and for that attempting various numbers of laboratory compaction tests at different proportions of various graded sand with bentonite is costly, laborious and time consuming. This study is an attempt to select the sand gradations and proportions for sand-bentonite mixtures. Results obtained through the laboratory investigation and mathematical technique (Percent Variance) reveals that by just knowing the MDD of bentonite and percentage of fine, medium and coarse sand; the maximum dry density of any sand-bentonite mixtures could be estimated within ±3% variation in actual and estimated values. Based on that selection of mix combination of sand-bentonite for liner can be identified as well as the quantity of soil required for any project work consequently, the cost for any earthwork project can be designed.