Stabilization of Lead and Zinc Nitrate-Contaminated Low Plasticity Clayey Soil Using Metakaolin Geopolymer

Abstract

ABSTRACT Contamination of soil threatens the environment and can have a negative effect on soil strength parameters. Soil stabilization is one way to address this issue. In the present study, metakaolin geopolymer was used to stabilize contaminated clay. Initially, the effects of the concentration on the soil parameters was investigated. A combination of lead nitrate and zinc nitrate at a 1:1 ratio was used to contaminate the soil by introducing 1000, 5000 and 10,000 ppm of contaminants. The samples were subjected to a 7-day curing period after which the Atterberg limits, compaction, unconfined compressive strength (UCS), California bearing ratio (CBR) and pH tests were conducted. The results showed that the addition of 10,000 ppm of contaminant to the base soil decreased the CBR, UCS and pH by 21.07%, 23.37% and 15.51%, respectively. The most critical contaminant concentration was found to be 10,000 ppm. Next, soil samples contaminated with 10,000 ppm of lead and zinc nitrates was stabilized with 5%, 10% and 15% metakaolin geopolymer at curing times of 7, 14 and 28 days. After stabilization, the tests initially conducted on the contaminated samples without stabilizer were performed on samples stabilized with metakaolin geopolymer. The outcomes revealed that the soil strength parameters increased significantly with increases in the metakaolin geopolymer content and curing time. An increase in the curing time was shown to increase the UCS. The findings demonstrated that, after 28 days of curing, the soil pH of the stabilized samples with 5%, 10% and 15% metakaolin geopolymer increased by approximately 43.4%, 49.2% and 50.65%, respectively, in comparison with the soil containing 10,000 ppm of contaminants without stabilizer.