Research On The Meso-performance Of Rubber Concrete Using Cohesive Crack Model

The rubber concrete ecological material that is prepared by using rubber particles as aggregates changes the ductility of the concrete while improving the ductility.Based on the cohesive crack model,the meso-construction of rubber concrete consisting of six phases of mortar,coarse aggregate,rubber granule,mortar-aggregate interface,mortarrubber interface and mortar-mortar interface is used as the entry point.The changes of rubber particle size,rubber content and interface strength on concrete performance were studied.The method of establishing two-dimensional random initial defect model of rubber concrete was proposed.The typical model failure modes with four initial contents were analyzed.The main work and conclusions of this paper are as follows:(1)Based on the requirements of the cohesive crack model and the random aggregate model,the embedding procedure and random aggregate placement procedure for the bonded crack unit of 0 thickness were prepared by using the secondary development of ABAQUS.A complete mesoscopic model of rubber concrete and a rubber concrete mesoscopic model with four different initial defects were established.(2)In this paper,the bond crack model and the random aggregate model are combined in the meso-mechanical model of rubber concrete to extend the traditional fivephase meso-rubber concrete to the six-phase composition of the mortar-mortar interface.The results show that the method can simulate the whole process of rubber concrete from the beginning of the force to the complete loss of bearing capacity.(3)The mesoscopic random aggregate model using the cohesive crack model is used to compare the typical failure and performance of rubber concrete and reference concrete under three conditions of uniaxial tension,pull fracture and bending fracture.Because the particle size and the amount of rubber particles are the main factors affecting the performance of rubber concrete,the research and analysis of the influence of the comprehensive parameters on the mechanical properties of rubber concrete are carried out.The results show that the introduction of rubber particles brings the low-rigidity "hole" into the mortar matrix,which is one of the main reasons for the decrease of the strength of rubber concrete;Under the three loads of uniaxial tension,pull failure and bending fracture,the mechanical strength of rubber concrete decreased,which decreased by 6.5%,10.9% and 4.5% respectively;The effect of the amount and particle size on the rubber concrete is comprehensive.(4)Adding rubber particles to concrete reduces the strength of concrete,but a reasonable reduction in the size of rubber particles can make rubber more evenly distributed in the mortar matrix,thus improving the strength and deformation capacity.This method is an effective way to improve the mechanical properties of rubber concrete.(5)The strength values of mortar-aggregate interface,mortar-rubber interface and mortar-mortar interface have an effect on the meso-simulated simulated strength value and ultimate strain of rubber concrete,and increase with the increase of interface strength;The influence of interface strength on the weak points inside the test piece is not obvious;For the three interfaces,the rubber concrete sensitivity order is: mortar-mortar interface strength> mortar-aggregate interface strength> mortar-rubber interface strength.(6)As the elastic modulus of the mortar increases,the ultimate stress of the rubber concrete increases continuously,and the ultimate strain decreases continuously.The elastic modulus of the aggregate and the elastic modulus of the rubber have little effect on the strength and deformability of the rubber concrete;The three kinds of elastic moduli have no obvious effect on the weak point inside the specimen.(7)Different content of mortar-aggregate interface microcracks,mortar-rubber interface microcracks,mortar-sand interface microcracks and mortar pore initial defects were prepared,and the influence of four on the mechanical strength of rubber concrete was studied by quasi-static loading.The final results show that the order of influence of the four initial defects is mortar-mortar interface microcrack> pore> mortar-aggregate interface microcrack> mortar-rubber interface microcrack.Among them,the influence of pores,mortar-mortar interface microcracks and mortar-aggregate interface microcracks is obvious,which cannot be ignored in design research.