Stress–strain relation and strength characteristics of cement treated zinc-contaminated clay

This paper presents an investigation of the influence of zinc concentration, cement content, and curing time on the strength characteristics of cement treated zinc-contaminated soils. Zinc-contaminated soil is artificially prepared by mixing concentrated zinc nitrate solution with a high-plasticity clay. The zinc concentrations are 0, 0.01, 0.02, 0.05, 0.1, and 0.2%. The contaminated soils are then solidified with cement, of which the contents are 12, 15, and 18%. Both zinc concentration and cement content are based on the oven-dried soil weight. A series of unconfined compression tests are performed at curing times of 7, 28, 56, and 90 d. The results reveal that the zinc concentration levels have significant influence on the brittleness/ductileness, unconfined compressive strength, strain at failure, and secant modulus of the soils. The relationships between the unconfined compressive strength and strain at failure/secant modulus are quantified. A simplified method is proposed for predicting the unconfined compressive strength of the cement treated zinc-contaminated soils. A comparison of the measured and predicted strength shows that the proposed method has a high accuracy.