Analysis of Shear Resistance and Mechanism of Construction and Demolition Waste Improved by Polyurethane

A large amount of construction and demolition waste (CDW) is generated during the construction of projects. In this paper, polyurethane foam adhesive (PFA) was used to improve the mechanical properties of CDW. The large-scale direct shear tests, California bearing ratio (CBR) tests and Scanning electron microscope (SEM) tests were carried out to study the variation regularities of mechanical properties of treated CDW during the laboratory tests. The test results show that the shear strength of CDW increases with the increase of PFA content, vertical pressure and the shear rate. However, the increase of vertical pressure on the shear strength of CDW is smaller than that of PFA, and the improvement of the shear rate is relatively small. The California bearing ratio (CBR) test also proves that PFA can effectively improve the bearing capacity of CDW and reduce the loss of CBR caused by the 4-day soaking. Scanning Electron Microscope (SEM) finds that polyurethane wraps multiple particles and enhances the internal connection, which results in the cohesion between the particles being greatly increased. The study presented in this paper will better assess the shear resistance of improved CDW with PFA as a substitute for pavement base materials in practical engineering applications.