Effect of Surfactant on Dry-Side Compaction of Silty Sand

Abstract

The use of surfactants with soil is an evolving practice that lacks a systematic theory to describe the mechanisms of behavior that influence the soil response. A technique has emerged from the theoretical modeling of partially saturated soils that allows near-optimum densities to be achieved with water contents well below optimum. The central theme of the model is a distinction between the intergranular stress caused by externally applied loads and the stress derived from internally distributed capillary stresses due to the presence of water menisci. A practical consequence of the theory is that resistance to compaction can be reduced by adding surfactant (soap) to the mix water to reduce the component of intergranular stress derived from capillary tension. The decrease in capillary tension permits greater dry-side compaction density and an increase in soaked California bearing ratio strength. Well-graded silty-sand data were used to compare the behavior of untreated specimens with that of specimens treated with a 4% by weight of water anionic surfactant. The treated specimens achieved dry densities near optimum with the use of 25% less total mix water. Differences in the California bearing ratio strength for the soaked and unsoaked specimens and comparison of specimens' swell during soaking support the concept that compaction was improved through reduction of capillary tension. This allows specified dry densities to be achieved using considerably less water, which is critical in arid environments, and translates into efficiency in cost and, more important for rapid military operations, in construction time.

Testing surfactants as additives for clay improvement: compaction and suction effects

“…The only exception is for the kaolin samples, where the maximum dry density dropped by 0.05 Mg/m 3 for the samples prepared at higher surfactant concentrations (1% and 4.5%). This finding contradicts the results by Berney et al (2003) where the maximum dry density was increased with the surfactants. Figure 4a shows suction against the surfactant concentration for a 50:50 sample at 10% and 15% water content.…”

“…A reduction in the maximum dry density did occur but only at high surfactant concentrations. The compaction results revealed that the explanation proposed by Berney et al (2003) whereby the maximum dry density is increased due to a reduction in suction does not hold for all soils and conditions. The maximum dry density changed little even when suction was reduced by 80% at 1% surfactant concentration.…”

“…Surfactants are classified into three groups according to the nature of the hydrophilic portion of the molecule: (1) anionic surfactants (negatively charged head group); (2) cationic surfactants (positively charged head group); (3) nonionic surfactants (non-charged) (Rosen, 1989). Sanchez-Martin et al (2008) found that polar surfactant adsorption towards clays would stabilize, whereas nonionic surfactant adsorption (including Triton X-100) would continue to increase above the CMC.…”

“…For example, cationic surfactants CTAC and QEFA were found to produce a dramatic change in clay plasticity. Within the effect of surfactants on soil compaction, Berney et al (2003) assessed the influence of a wetting agent on compaction, and found that the soil with the surfactant solution achieved a higher maximum dry density at the optimum water content than the sample only with water. The Authors justified it based on a reduction of suction.…”

Constitutive Analyses of Nontraditional Stabilization Additives

“…The account described here is summarized from Berney et al (2003), which investigated a silty-sand. Lambe (1954) reported a similar study for clays.…”