The effects of colemanite and ulexite additives on the geotechnical index properties of bentonite and sand-bentonite mixtures

© 2018, Springer Nature Switzerland AG.Bentonite-sand mixtures are generally used in landfill liners. The properties of bentonite-sand mixtures should not change by time. For that reason, it is necessary to improve the properties of bentonites and bentonite-sand mixtures. In this study, the boron minerals namely colemanite and ulexite were added to the bentonite and bentonite-sand mixtures in order to improve their consistency limits and compaction characteristics. The boron additives were added 5, 10, 15, 20% to the bentonite and the liquid limits and plastic limits were determined. The boron additives were added to the 10% bentonite + 90% sand and 20% bentonite + 80% sand mixtures and compaction characteristics were determined in the presence of colemanite and ulexite. As the ulexite ratio increased, the liquid limit value decreased, but as the colemanite ratio increased, the liquid limit value increased. The 20% ulexite and colemanite addition, decreased the liquid limit values of bentonite 8.4% and 13.8%, respectively. As the concentration of boron additives increase, the optimum water content of the mixtures increases. This effect is more significant at 10% bentonite + 90% sand. As ulexite and colemanite content increases the maximum dry unit weight of the bentonite-sand mixtures increase. The effect is more significant at the colemanite additive and at 10% bentonite + 90% sand mixture