Experimental study on mechanical properties of polyurethane-based composites

Conventional concrete is susceptible to damage under long-term loading due to its brittleness and susceptibility to cracking, affecting structural stability and durability. Polyurethane (PU) has good toughness and bonding ability, making it ideal for improving concrete properties. In this study, PU was mixed with cement and aggregate in a certain proportion to prepare PU-based composites to evaluate the effect of the content of each component on their mechanical properties. Polyurethane cement (PU-cement) was produced by mixing PU and cement, polyurethane mortar (PU-mortar) was made by adding standard sand to PU-cement, and polyurethane concrete (PU-concrete) was created by adding gravel to PU-mortar. The compressive and flexural properties of the three materials were tested, and the bubble characteristics of the fracture surfaces of the specimens were observed. The compressive and flexural strengths of PU-cement were 51.1 MPa and 31.1 MPa, respectively. Compared to PU-cement, the compressive and flexural strengths of PU-mortar were improved by 48.9 % and 10.9 %, respectively, and those of PUconcrete were improved by 28.4 % and 1.3 %, respectively. The highest flexural strength of the specimen is achieved when the number of bubbles and air content are minimized. Optimal flexural strength was achieved when bubble and air content were minimized. This study refined the proportions of PU-based composites and systematically evaluated their mechanical properties, demonstrating the importance of proper component proportioning in enhancing material properties. The findings also guide the application of PU-based composites in construction.