Impact of curing conditions on the microstructure of cement-stabilized sandy clay soils in coastal pavements

Abstract

Cement stabilization is employed to construct pavement layers with available sandy clay soil. This paper aims to demonstrate how curing under ambient hot weather conditions in coastal regions, along with the quality of water used, significantly impacts the targeted strength. The soil is subjected to a curing process at 1%, 2%, 3% and 4% cement dosages. This is conducted under conditions of high relative humidity, ambient weather, and subsequent immersion in pipe-born water or culvert water for a total duration of seven days. Microstructural, geotechnical and mechanical assessments are conducted. X-ray diffraction patterns and scanning electron microscope images revealed the presence of kaolinite, illite and quartz minerals, which produce calcium silicate aluminate hydrate compounds with cement. Energy dispersive X-ray mapping reveals the presence of residual calcium and aluminium compounds on samples that have undergone ambient curing. This phenomenon can be attributed to the rapid deceleration or cessation of hydration reactions, resulting from the premature loss of water through evaporation. Low strength, 0.4 MPa at 3% dosage, were recorded and the samples disperse when immersed. On the other hand, those cured in high relative humidity exceed 1.2 MPa and 1.3 MPa following immersion. The strength of samples immersed in culvert water is lower (1.3 MPa) than those in pipe-born water (1.5 MPa), indicating the negative impact of the carbonate and sulphate compounds in the culvert water. For sub-base pavement layers, the design cement index is 2% for medium traffic and 3% for high traffic roads, with watering during the first seven days.