Mechanical and microstructure analysis of mass-stabilized organic clay thermally cured using a ternary binder

The technique of mass soil stabilization using alternative binders to Portland cement (PC) has been used successfully in the past. However, knowledge gaps exist regarding the design of these binders. Ground-granulated blast furnace slag (GGBS) has been widely used as a substitute for PC; however, it requires an alkaline activator (e.g. lime and PC) to promote pozzolanic reaction and strength enhancement. A candidate that presents a less energy-intensive manufacturing and carbon footprint is carbide lime (CL), a by-product of acetylene gas production, rich in Ca(OH)2. The main problem with the pozzolanic binder in the stabilization technique is its slow reaction kinetics and the long time required for laboratory-scale investigations before in situ application. Therefore, this research presents a dosing study of a ternary binder (TB) comprising CL, GGBS and PC type III (CEM-III) to mass-stabilize a clayey organic soil using thermal curing as an innovative technique to improve the feasibility of laboratory-scale investigations. The effects of binder composition and thermal curing time on the evolution of strength, stiffness, mineralogy, and microstructure were determined. The results, supported by a statistical analysis (ANOVA) and by a multivariate regression analysis (MRA), have shown that the new TB produced a superior mechanical response to soil samples stabilized exclusively with CEM-III. This was evidenced by a less porous microstructure (more reaction products) and mainly the formation of a C–A–S–H gel, as a product of CEM-III hydration and alkaline activation of GGBS (blended cement), whereby the CL content played a key role for the development of the long-term pozzolanic reaction.