Study On Basic Properties Of Polyurethane Rubber Mixed Mortar

Polyurethane is a kind of polymer resin material and Polyurethane mortar(Polyurethane mixed with sand)is receiving more and more attention for being used as a repair material.In this study,both Polyurethane mortar and Polyurethane rubber mixed mortar(Polyurethane mixed with sand and rubber powder)are tested for their compressive strength and flexural strengths.The purpose is to evaluate the influence of rubber powder on their material properties.A bonded cement mortar experiment is also conducted with the bonding material being both Polyurethane mortar and Polyurethane rubber mixed mortar.The materials designed for this research are as follows.Polyurethane adhesive consists of two components A and B.A(Polyhydric alcohol)is a compound containing a hydroxyl group.B(MDI)is a compound containing a free isocyanate group.Two ratios of A and B components,5:1 and 6:1,were selected,respectively.The rubber powder has a particle size of 16 mesh and 60 mesh,and it replaces the sand volume at the rate of 0,5%,10%,15% in volume.In addition,ordinary cement mortar with a mix ratio of 1:3:0.5 was also casted.However,to evaluate and conduct a vast experiment test on basic properties of polyurethane rubber mixed mortar,a total of 54 designs and420 pieces of specimens were casted and tested.The main research results are as follows:The flexural strength of polyurethane mortar at 3h is 5MPa averagely,while the compressive strength is around 11 MPa.This suggests that polyurethane mortar can be used as a repair material.In comparison with the polyurethane mortar,the compressive and flexural strength of the polyurethane rubber mixed mortar has a small decrease at3 h and 6h,while there is a little increase at 24 h of curing age.The strength for containing 16 meshes is larger than that for containing 60 mesh.At the same time,when the ratio of A and B components of polyurethane adhesive is 6:1,the compressive and flexural strength of polyurethane rubber mixed mortar at 3h,6h,1d,3d,and 7d are higher than those with the ratio of A and B components being 5:1.Polyurethane rubber mixed mortar has higher interfacial bond strength when the curing age is 7d,Non-rubbered specimen with PU ratio of 6:1(PC2-0)has the highest strength of 12 MPa at 7d;however,as the rubber content increases and the rubber particle size decreases,the interfacial bond strength decreases continuously;In the case of unblended rubber particles,the polyurethane bond mortar made of two different proportions of A and B components was compared,and the joint strength of the test piece prepared by the ratio of 6:1 was larger.The results of the tensile bonding strength test show that the bond strength decreases compared with the non-rubber blank polyurethane mortar specimens;as the rubber particle content increases,the bond failure load of the test piece decreases.While the test also shows that the rubber particle size of 16 mesh has greater reduction incorporation results in the bonding tensile strength,compared with the particle size of60 mesh in polyurethane rubber mixed mortar sample.In this test,specimen PC2b-2has the highest tensile bonding test of 1.411 MPa.However,when the ratio of PU is 6:1,the rubber content of 5% and 10% with a particle size of 60 mesh,still shows a high bond strength,meeting the requirements of the repair project.The results of Polyurethane rubber mixed mortar on tensile strength is a novel work.The results of interfacial bonding strength test on the specimen of a composite of Polyurethane mortar and cement mortar have not been found in any public literature.