Investigation of Temperature Effect on Strength Properties of Polyurethane-Treated Sand

Abstract

This study focuses on the shear-strength properties of polyurethane polymer–treated sand stored at different temperatures. The triaxial test was performed at unconsolidated and undrained conditions on the specimen after 2 days of curing at room temperature and 1 day of curing at various temperatures. The effects of polymer content and dry density on strength properties were also considered. Polymer reinforcement mechanism was analyzed using scanning electron microscope images. Results indicated that the stress-strain relationship exhibited increasing ductility as temperature increased; the shear strength, energy absorption, and cohesion tended to decrease initially and then increase, while the friction angle remained stable at approximately 30°. The strength properties were in proportion to an increment in polymer content, and the trend became more apparent in a warmer environment. The shear strength, energy absorption, and cohesion increased up to about 2.4 MPa, 65 kPa, and 400 kPa, respectively. A higher dry density resulted in significant improvement in strength properties, except for a slight reduction in ductility, no matter the temperature. The presence of a polymer matrix formed a honeycomb and special net structures among sand via coating, bridging, and filling effects; hence, the treated sand turned into a whole system exhibiting favorable strength properties. This reinforcement effectiveness depended on polymer content, dry density, ambient temperature, soil grain, and polymer characteristics.