Effect Of Scattering Gravels In Self-compacting Concrete Surface On The Properties Of New-to-old Concrete Bond Strength

The resistance to shear force is too small and the deck interlayer is fragile because ofpoor interface bonding quality between the bridge deck pavement and bridge deck. Inorder to improve the bond quality between bridge deck and pavement, a new constructionprocess of scattering gravels into the surface of self-compacting concrete is put forward toreplace the process of roughening the surface of old concrete, while the roughness is oneof the important factors affecting the bonding quality between new and old concrete.The dosage of cementitious material and surface grout is higher than that in ordinaryconcrete, which provided good condition for the gravels scattered into the concrete surface.Specifically, through theoretical analysis and raw material selection, this paper producedbridge self-compacting concrete, and analyzed the main factors affecting the effects ofgravels scattered, raw materials selection, estimation method of gravels scattered, and theeffect of the process on the strength and elastic modulus of concrete. In order to study theeffect of scattering gravels in self-compacting concrete surface on the properties ofconcrete bond strength, the adhesive property of with the process of roughening thesurface, and scattering gravels with the diameters of5~10mm,10~20mm and5~20mmwere analyzed, through splitting tensile test and slant shear test, and combining with theshape characteristic of bond failure interface. The gravels were considered as reinforcedparticle, and rock failure process analysis (RFPA) code was used to study the failureprocess of slant shear specimens with different adhesive strength and reinforced particlesunder static loading respectively. The results of slant shear test of scattering gravels intothe surface were compared with that of the numerical simulation.The results showed that compared with the reference specimens, scattering gravelswith the diameters of5~10mm,10~20mm and5~20mm into the old concrete surfacecould increase the splitting tensile strength by29%,11%and24%respectively, and thetensile failure ratio of gravels in the bond failure interface were81%,37%and53%. Thesplitting tensile strength was increased more obviously with small size gravels. The slantshear strength were increased by29%,84%and107%separately. And the failure model of the specimens was changed from adhesive failure to cohesive failure. When the adhesivestrength of bonding surface was less than30MPa, the strength of slant shear specimenswith different strength grade concrete were similar depending on the adhesive strength.Otherwise, the strength of slant shear specimens increased with the concrete strengthgrade, and leveled around the overall axial compressive strength of the same concretespecimen at last. The size of single reinforced particle almost had no influence on theelasticity modulus and strength of slant shear specimens. The large size of multiplereinforced particle was much benefit to improve the strength of slant shear specimens, andthe adhesive surface was no longer the weak position.