Effect of fine particles on cement treated sand

Cement treated sand improves mechanical properties through the cementitious bonding between cohesionless particles, thus allowing several geotechnical applications such as soil stabilization against slope failure and liquefaction. Since pure sand without any fine particles is seldom available in nature, this study aims to investigate the effect of fine particles (kaolin) in a very small proportion (<5%) on cement treated sand. Two types of cements are used: (i) Ordinary Portland cement (OPC) and (ii) Calcium sulfoaluminate cement (CSA). OPC is the widely used cementitious binder whereas CSA is a rapid hardening cement that is becoming popular due to its low carbon foot print. Three different cement contents (3%, 5% and 7%) and four different fine contents (0%, 1%, 3% and 5%) for each cement content are chosen. The stiffness and strength of the cement treated sands are measured through shear wave velocity and unconfined compressive strength respectively, after 1-day and 7-day curing periods. The results show that the influence of fine particles is visible even with fine content as low as 1%. However, the effect is different between the two types of cements used and between low and high cement contents. As the fine content increases, the increase in strength and stiffness is more for OPC than CSA and more significant at low cement content (3%) than high cement content (5% and 7%).