Research On Shrinkage Performance Of RPC/NC Bonded Specimen

In the process of repairing ordinary concrete with Reactive Powder Concrete(RPC),its early drying shrinkage may cause shrinkage stress and adversely affect the interface proper-ties at the bonding interface between reactive powdered concrete and ordinary concrete(RPC/NC).Therefore,this paper has experimentailly studied the shrinkage development law of RPC/NC bonded specimens,and on this basis,the stress distribution of the bonding inter-face due to shrinkage was analyzed by numerical simulation.The main work and conclusions are as follows:(1)The free shrinkage of RPC under natural curing has been measured,the two variables of steel fiber dosage and specimen length has been controled,and the development law of RPC free shrinkage has been analyzed.The shrinkage of RPC/NC bonded specimens under natural curing has been measured,and three variables has been controled:interface dimen-sions,specimen thickness,and steel fiber content,and.the shrinkage development rules of RPC/NC bonded specimens has been analyzed.The results has showed:under natural curing,RPC drying shrinkage fitted an exponential function,Steel Fibers restrained RPC Free Shrinkage and RPC/NC Bond Specimen Shrinkage,interface lengthening and widening has increased interface restraint,the increase in the thickness of the test piece has weakened the interface restraint.(2)Temperature Diffusion in ABAQUS has been used to Replace Moisture Diffusion to Simulate RPC Free Shrinkage,interfacial Bonding Unit Cohesive Element has been used for Interface Slip of RPC/NC,a shrinkage finite element model for RPC/NC bonded specimens has been establised,and Compared with the finite element model that does not consider the interface bond slip.The results show that:when the finite element model is used to simulate the shrinkage of RPC/NC bonded specimens,the interface of the bond slip must be consid-ered.By calculating the effective steel fiber content of different test pieces,influence of Fi-bers on Moisture Diffusion of Concrete has been considered and Method of Elastic Modulus of Fiber Reinforced Concrete has been calculated,Quantitative analysis of the effect of steel fiber content and test piece size on the finite element model.(3)The interfacial shrinkage stress results of the RPC/NC finite element model with the interface bond slip considered and the interface shrinkage stress results of the RPC/NC finite element model without interface bond slip considered are compared and analyzed,the interfa-cial shrinkage stress results of the RPC/NC bonded specimens calculated by the non-bonding slip theory and the interfacial shrinkage stress results of the RPC/NC bonded specimens cal-culated by the bond-slip theory are compared and analyzed.The results show that:when the interface shrinkage stress of RPC/NC bonded specimens is calculated theoretically or numer-ically,the bond slip of the interface must be considered.(4)The numerical simulation method was used to analyze the interfacial shrinkage stress of RPC/NC bonded specimens,and the following conclusions were drawn:The normal stress of cracking is positively symmetric across the mid-span,and it is a parabolic distribution with an opening downwards.Both the lengthening and widening of the bonding interface and the reduction in the thickness of the test piece increased the cracking normal stress.The shear stress was related to the antisymmetry in the midspan.Its distribution law was related to the interface size and the thickness of the test piece.when the interface length increased,shear stress changed from linear to nonlinear distribution.When the thickness of the test piece in-creased,the shear stress changed from linear to linear.Bifurcation.(5)Comparative analysis of the reparing of bridge decks of 32m simple-supported boxgirder bridges using RPC and ordinary concrete resulted in the following conclusions:RPC is an ideal repair material that reduces the height of the building and improves durability com-pared with ordinary concrete.