Minimizing the Detrimental Role Of Clays in Deep-Mixing with Chemical Additives-Paper

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The study investigates whether an anti-clay polymer (ACP), commonly used in tunneling, can reduce clay adhesion and improve workability and strength in deep soil mixing (DSM). Clay-rich soils are difficult to blend uniformly with cement: clay lumps and clogged mixing tools can create inhomogeneous columns with highly variable and often low strength.<br /><br />Laboratory tests were conducted on kaolin and sodium bentonite, which differ substantially in clay activity. Researchers measured viscosity and Atterberg limits at varying ACP concentrations, then tested the unconfined compressive strength (UCS) of cement-treated specimens prepared with different amounts of water, ACP, and cement.<br /><br />ACP reduced viscosity in both soils, with effects comparable to increasing water content. It also lowered the liquid limit, while having little effect on the plastic limit. Kaolin showed a marked response at low ACP concentrations, whereas bentonite’s liquid limit continued to decline as ACP dosage increased. These results indicate that ACP improves flow and workability by dispersing clay particles and making more water available in the mixture.<br /><br />Adding ACP alone could slightly reduce strength, but this effect may be offset by reducing mixing water and using the improved workability to incorporate more cement. UCS results also showed a relationship between strength and the soil’s residual consistency after accounting for water required for cement hydration. The authors conclude that ACP could support more homogeneous, stronger DSM columns and potentially reduce strength variability. However, the strength findings are preliminary and require further testing.

Keywords

anti-clay polymer

deep soil mixing

clay adhesion

workability

unconfined compressive strength

kaolin

sodium bentonite

viscosity reduction

liquid limit

cement-treated soil