Improved Mechanical Performance of Gravel Reinforced by Polyurethane Polymer Adhesive

This study evaluates the effectiveness of a polyurethane polymer adhesive (PPA) in reinforcing a uniformly graded gravel. A series of laboratory tests were carried out to study the permeability, strength, and deformation of gravels improved with different contents of PPA. The permeability of PPA-reinforced gravels under the same compaction effort was observed to decrease as the content of PPA increased, but was still higher than those of sand. PPA-reinforcement can increase the strength while reduce the contraction capability of gravels. Despite of the strength improvement, the ductility of gravels reduced with the increasing content of PPA. Upon shearing, the secant modulus kept decreasing until approaching a stable value, where the decreasing rate became higher as the content of PPA increased. An optimum content of PPA around 4% can be suggested, where a compromise between the moderate ductility and high strength/stiffness of PPA-reinforced gravels can be reached.