Effect of lime addition on the particle size fractions and microstructure of a clayey silt.

This work evaluates the stabilizing effect of lime addition on the geotechnical, physic-chemical, and microstructural properties of a class A-6 clayey silt. The results obtained show that lime contents of 3–6% lead to changes in grain size that modify the rheology of the material, thus improving the use properties. Compressive strength (3.89–5.95 MPa) and California bearing ratio (CBR 33–54%) increase by 52.95% and 63.63%, respectively. With 6–9% lime, the compressive strength (5.95–4.58 MPa) and CBR (54–41%) decrease by 23% and 24.04%, respectively. The 6% lime content is the point of lime fixation beyond which the mechanical properties of the soil no longer improve. Indeed, the addition of lime reduces the clay fraction (29.45–17.29%) and the silt fraction (45.12–33.05%) by 41.29% and 26.75%, respectively, while the sand fraction (25.43–49.66%) has an increase of 95.28%. The sand content increases considerably and leads to a decrease in the dry density and plasticity of the mix. The increase in sand content leads to a bimodal pore size distribution (micropores and macropores), which results in a flattening of the compaction curves (Proctor) and an increase in the optimum water content. To overcome the negative correlation between compressive strength and strain at failure, the lime-treated pavement layer must be placed on a solid substrate. The results obtained from the effect of lime on the grain size fractions are confirmed by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX). The disparity in the statistical properties and distribution characteristics of the particle size fraction data is due to the fact that the soil–lime combination does not obey the law of mixtures. [ABSTRACT FROM AUTHOR]