Effect of Carbonation on the Engineering Properties and Microstructural Characteristics of Cement Solidified Lead-Contaminated Soils

摘要

Carbonation of cement-treated soils results in physical and chemical transformations that can affect the long-term effectiveness of stabilization/solidification. In order to ensure safety of further utilization, it is necessary to investigate the effect of carbonation on the performance of cement-solidified contaminated soils. Artificial contaminated soils with different lead contents were solidified using cement, moisture content, density, pH value, strength, and microstructure of solidified samples before and after carbonation were tested. The experimental results show that carbonation decreases moisture content of samples, and increases dry density. Unconfined compressive strength of carbonated samples is 5-25% higher than that of non-carbonated samples. The pore solutions of non-carbonated samples are highly alkaline (pH=11-12), whereas those of carbonated samples exhibit lower pH values (pH=8-9). Thermogravimetric analysis test and scanning electron microscopy test results confirm the transformation of cement hydration products to calcium carbonate during the carbonation process.