Abstract: Limestone calcined clay cement (LC3) is an environment-friendly and sustainable cementitious material. It has recently gained considerable attention for the stabilization/solidification (S/S) of soils contaminated by heavy metals. However, the existing studies on S/S of Zn-contaminated soils using LC3 in terms of hydraulic conductivity and microstructural properties as compared to ordinary Portland cement (OPC) are limited. This study focuses on the evaluation of the mechanical, leaching, and microstructural characteristics of Zn-contaminated soils treated with different contents (0%, 4%, 6%, 8%, and 10%) of low-carbon LC3. The engineering performance of the treated Zn-contaminated soils is assessed over time using unconfined compressive strength (UCS), hydraulic conductivity (k), toxicity characteristic leaching procedure (TCLP), and synthetic precipitation leaching procedure (SPLP) tests. Experimental results show that the UCS of Zn-contaminated soils treated with LC3 ranged from 1.47 to 2.49 MPa, which is higher than 1.63%‍–‍13.07% for those treated with OPC. The k of Zn-contaminated soils treated with LC3 ranged from 1.16×10^-8 to 5.18×10^-8 cm/s as compared to the OPC treated samples. For the leaching properties, the leached Zn from TCLP and SPLP is 1.58‍–‍321.10 mg/L and 0.52‍–‍284.65 mg/L as the LC3 contents ranged from 4% to 10%. Further, the corresponding pH modeling results indicate that LC3 promotes a relatively suitable dynamic equilibrium condition to immobilize the higher-level Zn contamination. In addition, microscopic analyses demonstrate that the formations of hydration products, i.‍e., Zn(OH)₂, Zn₂SiO₄, calcium silicate hydrate (C–S–H), calcium silicate aluminate hydrate (C‍–‍A‍–‍S‍–‍H) gel, ettringite, and CaZn(SiO₄)(H₂O), are the primary mechanisms for the immobilization of Zn. This study also provides an empirical formula between the UCS and k to support the application of LC3-solidified Zn-contaminated soils in practical engineering in the field.

可持续石灰石煅烧粘土水泥(LC3)固化剂处理锌污染土的环境岩土特性及微观结构特征

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