Investigating the synergistic effect of using cement, polymer slurry, and recycled tire fibers in improving the mechanical and geotechnical properties of dune sand

Since one of the major problems is these sands, its low resistance to natural moisture and saturation conditions, a laboratory study was conducted to investigate the effect of adding polyvinyl alcohol polymer to improve the mechanical and geotechnical properties of dune sands. The results revealed that the addition of this polymer up to 0.2 weight percent increases the maximum dry weight and does not significantly change optimal moisture. The experiments also showed that by increasing the polymer content, the CBR resistance of the samples increased significantly, so in samples made with 0.5 % of the polymer, the CBR value reached 185; this amount is more than 7.5 times the CBR for neat soil. Experiments showed that by adding 2% cement to the mixture, the resistance of the samples was increased, and their resistance to scouring increased. The direct shear test results indicated that the addition of polymer also significantly increased the shear strength of the samples. Tire fibers were used to prevent this condition and made the samples more ductile. The optimum amount of fiber needed was 0.6% in this case. The results of single-axial tests also showed that adding polyvinyl alcohol increases the soil's compressive strength and shear strength considerably. For example, in a combination of 0.4% polyvinyl alcohol, 1% cement, and 0.6% tire fiber with sand, the compressive strength reached approximately 15 kg/cm2, while the compressive strength for 1% sand cement was about 0.29 kg/cm2.