Influence of admixtures on the characteristics of aqueous foam produced using a synthetic surfactant

Foam characteristics, including density, stability, and texture, influence the properties of end products like foamed concrete. The present work investigates the individual and combined influence of xanthan gum and low-cost sodium-based admixtures (NaOH, NaCl, and Na2CO3) on the viscosity of sodium lauryl sulfate (SLS) foaming solution and the foam characteristics. Where xanthan gum induced its characteristic pseudo-plastic behavior to the foaming solution, the addition of sodium-based admixtures did not affect the Newtonian behavior of the SLS solution. The addition of sodium-based admixtures elevated the critical turbidity and Krafft temperature of the surfactant solution. Xanthan gum substantially reduced the liquid drainage and improved stability to a great extent. However, the increment in foam density was more gradual with increasing xanthan gum dosage, following an increase in lamella thickness. Sodium-based admixtures significantly increased the density of foam while reducing the bubble sizes. Further, the SLS solution admixed with xanthan gum and sodium-based admixture resulted in foam with properties intermediate to the foams stabilized with individual admixtures. The resulting foam had a higher density and a smaller mean bubble size than unstabilized or xanthan gum stabilized foam. In contrast, the stability was more increased compared to unstabilized or sodium-based admixture stabilized foam.