Effect of Grain Size and Porosity/Binder Index on the Unconfined Compressive Strength, Stiffness and Microstructure of Cemented Colombian Sands

Artificial cementation of granular soils results in improved stabilization, increased stiffness, and greater mechanical strength. The porosity index and volumetric cement content $\left(\eta /{C_{iv}}^a\right)$ is presented as a key measure to study the evolution of different soil stabilization types. However, this index had not been previously studied or adjusted for sands in Colombia. Therefore, this study evaluates the applicability of the $\left(\eta /{C_{iv}}^a\right)$ index on unconfined compressive strength $({\mathit{q}}_{\mathit{u}}$) and stiffness ($G_o$), complemented by microstructural analysis, in four sandy soils from Luruaco (Atlántico), Lorica (Córdoba), Medellín (Antioquia), and Bogotá D.C. The soils were stabilized with Type III Portland cement in dosages of 3%, 5%, 7%, and 9%, and subjected to UCS, ultrasound, and SEM-EDS tests after a curing period of 7 days. It was found that increasing cement content results in higher ${\mathit{q}}_{\mathit{u}}$ values for the samples, and higher molding density also leads to higher ${\mathit{q}}_{\mathit{u}}$ values. Additionally, the grain size distribution influenced the adjustment of parameter “a”. In the sands from Bogotá and Lorica, with high uniformity, the value of “a” was 1.00. In contrast, mineralogy and particle shape played a predominant role in the sands from Medellín and Luruaco, where the coefficient of uniformity is higher, suggesting a possible inverse relationship between particle angularity and the value of “a”.