Sustainable soil stabilization: Evaluating the feasibility of hydraulic cement in the deep mixing method

This research evaluates the potential of Hydraulic Cement (HC) as an environmentally sustainable alternative to Ordinary Portland Cement (OPC) in soil stabilization using the Deep Mixing Method (DMM), a widely employed technique for improving weak soil deposits. The study focuses on two distinct soil types, Bangkok Clay and Mekong Sand, treated with varying cement contents (10 %–30 %) of HC and OPC, and examines their unconfined compressive strength (q u ) and secant modulus (E 50 ) over curing periods ranging from 3 to 90 days. Results indicate that both HC and OPC significantly enhanced q u and E 50 , with the most substantial gains observed within the first 28 days, followed by a slower rate of improvement. OPC-treated soils generally exhibited higher q u and E 50 values at lower cement contents, attributed to its higher SiO 2 and Al 2 O 3 content, which accelerates pozzolanic reactions and strengthens early-stage cementation. However, HC-treated soils demonstrated comparable performance to OPC-treated soils at higher cement contents (≥25 %), driven by HC's higher CaO content, which compensates for its lower SiO 2 and Al 2 O 3 content, particularly in sandy soils. Empirical formulas were developed to predict the required cement content for HC-treated soils based on pre-design q u values. These formulas were validated through field testing, with results showing q u and E 50 values exceeding laboratory predictions by up to 64.42 % and 77.65%, respectively. The higher-than-expected field performance was attributed to increased cement content used to address challenges in achieving uniform mixing under field conditions. SEM analysis revealed that the initial differences in hydration products between HC and OPC diminished over time, indicating that HC-treated soils can achieve comparable long-term performance to OPC-treated soils. These findings highlight the viability of HC as a sustainable alternative to OPC for soil stabilization in DMM applications, providing significant environmental benefits by reducing CO 2 emissions. This research contributes to advancing sustainable engineering practices in geotechnical applications, supporting efforts to mitigate the environmental impact of cement use in construction projects while ensuring effective and durable soil stabilization.