Low-Carbon Stabilization of Expansive Soils Using Cement Kiln Dust and Calcium Carbide Slag: Mechanisms and Performance

Qiangzhen Yan ¹ Bo Peng ¹ Wenwei Li Li ^2* Baotian Wang ³ Jinyu Zuo ³ Guangdong Lv ⁴ tongzhang Wang ⁵

• ¹ Gansu Institute of Engineering Geology, Lanzhou, China
• ² Shandong University, Jinan, Shandong Province, China
• ³ Hohai University, Nanjing, Jiangsu Province, China
• ⁴ Tibet Agriculture and Animal Husbandry College, Linzhi, China
• ⁵ Jiangsu Hehai Engineering Technology Co., Ltd, Nanjing, China

In pursuit of eco-friendly soil improvement strategies, this study explores the synergistic potential of cement kiln dust (CKD) and calcium carbide slag (CCS) for expansive soil stabilization.Laboratory investigations encompassed compaction tests, free swelling rate measurements, unconfined compressive strength (UCS) assessments across multiple curing periods, and scanning electron microscopy (SEM). Results indicate that combined CKD-CCS formulations significantly outperform single-stabilizer systems, achieving higher densification, lower swelling ratios, and enhanced mechanical strength. Specifically, a 10% CKD-9% CCS mixture attained a maximum dry density of 1.64 g/cm ³ , reduced the free swelling rate to 22.7% at 28 days, and reached a UCS of 371.3 kPa. SEM images revealed a denser soil matrix with extensive hydration product formation, including calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H), which fill interparticle voids and strengthen interparticle bonds. CCS promotes early-stage strength through rapid hydration, while CKD sustains long-term strength via progressive development of C-S-H gels.Together, these dual mechanisms optimize mechanical performance and volumetric stability.Consequently, CKD -CCS blends provide a promising low-carbon alternative for expansive soil stabilization, offering both immediate and sustained performance improvements compared to traditional stabilizers.