Research Specifications

The hardfill embankments are composed of cemented sand-gravel (CSG) mixtures. In some cases, however, sand and gravel used in the mixture contain fine-grained fraction. This paper aimed to study the mechanical behavior and microstructure of CSG mixtures in which the base soil contains fine-grained particles with different plasticity specifications. Various contents of kaolinite and bentonite were added to a sand-cement mixture with different cement contents and uniaxial strength and deformation modulus in the mixtures were measured at two curing ages. According to the results, in low cement mixtures, the mixture containing 10% of the additive exhibited the maximum strength and deformation modulus, regardless of the additive type. In a family of bentonite-containing mixtures with higher cement, the strength of mixtures decreased with increasing the bentonite content. However, the mixture with higher cement and 10% of kaolinite presented the best performance from in terms of strength and stiffness. Analyzing the mineralogy and SEM images of mixtures showed that the structure of base soil attained the best packing and a strong matrix was devolved inside the mixture with 10% of fine additive. Furthermore, the kaolinite particles in the mixture containing 10% kaolinite contributed to the hydration process of cement.