Experimental Study On Bonding Properties Between Deformed Steel Bars And Scattering-filling Coarse Aggregate Concrete

Pumped concrete has the advantages of strong maneuverability and high efficiency.The pumped concrete is mixed in the mixing station and sent to the construction site through the transport vehicle,which reduces noise and environmental pollution.It has been widely used in civil engineering.However,in engineering practice,especially in high-rise building construction,the pumping concrete structure will have early cracking phenomenon,among which the crack problem of the floor is the most serious,and it has become a common quality problem in the project.Scattering-filling coarse aggregate concrete is that a certain volume fraction of coarse aggregate is added to the reference concrete.The use of coarse aggregate can increase the amount of coarse aggregate,and constitute "coarse aggregate interlocking concrete".The early crack resistance is better.In order to study the bond performance between deformed steel and scattering-filling coarse aggregate concrete,the curve characteristics,bond failure mechanism and failure mode of deformed steel and scattering-filling coarse aggregate concrete were analyzed by drawing test.The scattering-filling rate,anchoring length,the influence of the thickness of the protective layer,the diameter of the steel bar and the ratio of the hoop on the bond performance of the scattering-filling coarse aggregate concrete were discussed and establish the ultimate strength formula of the bond anchorage;The post-mixing rate and the anchor length parameter are discussed through the beam test.The influence of the bonding properties of scattering-filling coarse aggregate concrete is compared with the pull-out test,and the ultimate strength formula which is more in line with the actual engineering is given.The bonding stress of different positions in the anchorage length of the scattering-filling coarse aggregate concrete is obtained by the method of strain gauge on steel surface.The law of relative slip distribution,the law of ?-s relationship with anchor length,and the position function reflecting the law are got.The bond constitutive relationship between steel bars and scattering-filling coarse aggregate concrete considering the anchor position is gave;The statistical formula of the bond strength,combined with the reliability analysis,gives the anchorage length of the steel bar after scattering-filling coarse aggregate concrete,which is for advice on actual projects.The results show that the bond strength of the scattering-filling coarse aggregate concrete is improved and the maximum is reached after the scattering-filling rate is 20%.The bond-slip curve of the scattering-filling coarse aggregate concrete is similar to that of ordinary concrete and has experienced the micro-slip phase,slip phase,pull-out phase,descending phase and residual phase;the bond failure mode of deformed steel bar and scattering-filling coarse aggregate concrete is mainly splitting failure,and shear failure when the stirrup is transversely constrained;Compared with the pull-out test,the bond strength between the steel bars of the beam test and the scattering-filling coarse aggregate concrete is smaller.