Strength and microstructure characteristics of cement-based solidified/stabilized zinc-contaminated kaolin

An experimental investigation of Atterberg limits, unconfined compressive strength, secant modulus, pH of soil and microstructure characteristics of cement-treated zinc-contaminated kaolin is presented. The zinc-contaminated soils are artificially prepared with various zinc concentrations (0%, 0.01%, 0.02%, 0.05%, 0.1%, 0.2% and 0.5%), cement contents (8%, 12%, 15%, and 18%), and curing time (7 d and 28 d). The test results of Atterberg limits show that the liquid limit and plastic limit decrease with the increase of the initial zinc concentration in the soils. The unconfined compressive strength decreases with the increase of the initial zinc concentration. The pH values of the soils are significantly affected by the initial zinc concentration. The secant modulus (E₅₀) decreases as the initial zinc concentration increases. The scanning electron microscope pictures show that as the initial zinc concentration increases, the quantity and morphology of major cement hydration products change significantly. The test results of mercury intrusion porosimetry demonstrate that with the increase of the initial zinc concentration, the quantity of soil pores with diameter of 1 to 10 μm increases, whereas that of pores with diameter of 0.01 to 1 μm decreases.