Effects of LC3 on the unconfined compressive strength of clay soils

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4. Effects of LC3 on the unconfined compressive strength of clay soils

Soil improvement aims to reduce permeability, plasticity, shrinkage/swelling potential and to increase strength and stiffness. Portland cement (PC) is frequently used in the geotechnical field as a chemical soil improvement material. Given the energy consumed and excess CO₂ produced in PC production, it is vital to reduce cement consumption to increase economic and ecological sustainability. Recently, researchers have been investigating the use of alternative materials with lower CO₂ emission and production cost compared to PC in ground improvement applications. In this study, the effect of using limestone calcined clay cement (LC3) and nano-CaCO₃ on the unconfined compressive strength of soils was investigated in accordance with ASTM D1633 Method B. This study reveals for the first time the synergistic effect of the LC3 system containing nanomaterials on the unconfined compressive strength of high-plasticity soils as an alternative to traditional Portland cement-based binders. First, a high plasticity clay soil (CH) sample was prepared by mixing 90% kaolin and 10% bentonite. Mixture containing 15% of PC was considered as a control mixture. Then LC3 (containing 53% PC, 2% gypsum, 30% metakaolin and 15% limestone powder) was formed as a second treated mixture. And, as a third mixture, 5% nano-CaCO₃ was substituted for 15% limestone powder in the second mixture. Unconfined compressive strength (UCS), Axial strain at failure, (_f), Undrained shear strength (c_u), Modulus of elasticity (E₅₀), Toughness values were measured after 1 and 7 days of curing. Compared to the soil specimens improved with PC, the 7-day UCS values of the LC3 and LC3 with nano-CaCO₃ mixtures are only 26.4% and 33.8% lower, respectively. Additionally, the highest E₅₀ value was measured in the mixture containing LC3 at the end of the 1-day curing period. LC3 reduces CO₂ emissions by up to 40% compared to PC and the low cost provided by the global abundance of the clay and limestone in its content. It is thought that LC3 is a sustainable alternative in soil improvement studies.

International Conference on Advances and Innovations in Soft Soil Engineering (ICAISSE2026)

Ground Improvement and Low-Carbon Solutions