Desert silty sand modified by anionic PAM and ordinary portland cement: Microfabric reinforcement and durability

Abstract

The modification of desert silty sands has been a great challenge due to its relative uniform particle dimension and non-cohesion. This paper presents a study on utilizing a new additive, anionic polyacrylamide (PAM) with ordinary Portland cement (OPC) to modify the desert silty sand. Unconfined compression strength (UCS) tests were conducted to investigate the strength and durability (resistance to cyclic wet-dry and freeze–thaw damage) of modified sands at the maximum dry density; the scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) spectroscopy tests were carried out for microstructural analysis. Results reveal that the PAM fraction has a significant influence on the mechanical performance of the modified desert silty sand, and a threshold PAM dosage exists, beyond which adding excessive PAM will inhibit the strength and durability further. The microstructural analysis reveals that the physical stick-up of the PAM-to-sand particles leads to the formation of the spatial cobweb-like reticular structure. The Ca2+ cation released by OPC served as a cationic bridge, which in turn enhance the PAM adsorption efficiency. However, excessive PAM would play a negative role, chiefly because of the excessive accumulation between the hydrated production and sand particles. This study indicates that the combination of cement and PAM has the virtues of both cement-stabilized and PAM microfabric-reinforced sand. This binary PAM–OPC modification approach plays a more efficient role if a rational PAM incorporation (0.1–0.3 % in this study) is selected.