The Study On Mechanical Properties Of Polyurethane Concrete Molded By Reaction Injection

The effect of polyurethane grouting in repairing structures depends not only on the mechanical properties of pure polyurethane or concrete,but also on their composite mechanical properties.In order to figure out the mechanical properties of polyurethane concrete（PC）,the specimens were molded by reaction injection,and the uniaxial compression test and three-point bending test of PC specimens were carried out.Meanwhile,the specimens were observed by electron scanning microscope before and after the tests.The microstructures of the specimens before and after the test were compared and analyzed.To study the influence degree of multiple factors on the PC’s compressive and flexural strengths quantitatively,gray correlation degrees are calculated by gray relational analysis.The results show that the order of multiple factors affecting compressive strength is specimen’s density,M_polyurethane/M_total,void fraction and aggregate gradation.The order of factors affecting bending performance is:aggregate gradation,M_polyurethane/M_total,specimen density,loading rate and void fraction.In uniaxial compression test,based on concrete classical model,three-stage model for single-sized PC was developed.The theoretical mechanical model for dense-graded PC was proposed based on damage theory.The former model is more suitable for single-sized PC,while has less parameters.The latter model is suitable for both single-sized and dense-graded PC.In the three-point bending test,there is a good linear relationship between the load and deflection for single-sized and dense-graded PC.To describe the meso-mechanical behavior of PC,a random aggregate model was established based on Monte Carlo method.The model gives the polyurethane crushed foam model and gives the aggregate concrete plastic damage model for numerical analysis.In the numerical analysis of compression and three-point bending tests,the results show that the stress mainly concentrates on the interface transition zone between polyurethane and aggregate.