Experimental investigations on the physical and rheological characteristics of sand–foam mixtures

Abstract

Sand–foam mixtures have shown potential applications in land stabilization for mine tailings, drilling, and other areas of engineering. A series of laboratory experiments were conducted to examine the effects of foam–water ratio, sand concentration and time history on the physical and rheological properties of sand–foam mixtures. Sand particles of D50=0.21mm diameter were used with sand volumetric concentrations ranging from co=0.0–0.82. Physical properties such as density, air volume fraction and spreading of sand–foam mixtures with rheological properties including shear stress and viscosity were measured. Two different regimes of low and high concentrated mixtures were identified based on sand concentration with a critical sand concentration of co=0.6. It was found that the foam spreading rate is independent of foam–water ratio for low concentrated mixtures whereas for dense sand–foam mixtures, the foam–water ratio plays an important role in the fluidity of the mixtures. Rheological study of sand–foam mixture indicated that the yield stress increased with sand concentration. It was found that the viscosity of both foam and sand–foam mixtures decreased with shear rate indicating a shear thinning behavior. A shear banding effect was observed in low concentrated sand–foam mixtures for the shear rate ranging from 20 to 100s−1. Step-wise loop tests were performed to examine the sample degradation characteristics of sand–foam mixtures. It was found that the effect of time history on sand–foam viscosity is noticeable and viscosity of the sheared sample can be lower than the fresh and un-sheared sample for dense sand–foam mixtures.