Effect of curing stress on lime and cement-treated soil: X-ray tomography and mercury intrusion porosimetry investigation

As the use of non-renewable resources in civil engineering construction is increasingly being replaced, soil improvement for innovative construction works is becoming more widespread. Starting from soils with poor mechanical properties, it is possible to obtain durable materials by adding lime and cement composed of by-products from the metallurgical industry. The growing knowledge of cemented soils allows them to be used for the eco-design of infrastructure works. For example, they can be placed at depths greater than 10 m in embankments adjacent to linear transport infrastructures. To understand the evolution of these low-carbon materials when placed at depth, it is necessary to subject them to curing stresses in laboratory conditions. This paper explores the coupled effect of curing time and pressure using X-ray diffraction, mercury intrusion porosimetry, and X-ray tomography. Tomographic images are innovatively obtained while soil specimens are cured under an isotropic stress of 300 kPa. This imaging shows that these curing conditions involve porosity refinement, consistent with mercury intrusion porosimetry results. The most striking observation from X-ray tomography is that pore shape depends on pore volume. Furthermore, scanning enables observation of 3D variations showing the erosion of anhydrous lime grains during their hydration. These results demonstrate that accounting for curing pressure in cemented soil structures exceeding 10 m depth is key to optimizing their engineering potential.