| Reactive Powder Concrete(RPC)is a new type of cementitious composite material with ultra-high strength,high toughness and high durability,which can be used as a new material to improve engineering structures and extend the service life of structures.When using reactive powder concrete for repair and reinforcement of ordinary concrete,the transfer of shear load at the location of the bond surface requires good bonding performance,and the slip caused by insufficient shear bond strength can lead to cracking of the bond surface,reduced bearing capacity or even lead to premature failure of the construction.Therefore,it is of great significance and value to study the bonding performance of the bonding surface of activated powder concrete and plain concrete.The main studies carried out in this paper are:(1)Mechanical properties tests of concrete materials were carried out.Referring to the Standard for Test Methods of Physical and Mechanical Properties of Concrete(GB/T50081-2019)and Reactive Powder Concrete(GB/T 31387-2015),cubic compressive strength test,prismatic compressive strength test and static compressive elastic modulus test were conducted to obtain test parameters for finite element simulation.(2)The effects of keyway depth,keyway width,keyway shape and number of keyways on the shear bearing capacity and damage mode of the RPC-NC interface were analyzed through the study of direct shear tests on the keyway specimens at the RPC-NC interface.The optimal keyway size was determined by analyzing the interface shear strength and shear stiffness and load-slip curves.(3)A finite element model was developed based on the shear specimens at the RPC-NC interface.Considering the reactive powder concrete as a two-phase inhomogeneous composite consisting of concrete matrix and basalt fiber reinforcement,the Python code of basalt fiber was written by random placement method.By comparing the damage modes and load-slip curves of the specimens,the results of the numerical simulation are in better agreement with the experimental results,and the established RPC-NC finite element model can simulate the RPC-NC interface bond shear performance more accurately.(4)By establishing the finite element model of RPC-NC interface keyway construction to study its stress process and damage mode,the dimensional effect,post-cast RPC strength,number of keyways,basalt fiber admixture,use of interfacial agent,and magnitude of lateral stress of RPC-NC specimens in shear performance were parametrically analyzed.(5)The formulae for calculating the bearing capacity of old and new concrete joint proposed by national codes and other scholars are introduced,and the practical range of their formulae is analyzed.Then the formula of shear bearing capacity of RPC-NC interface is derived based on the principle of stress molar circle,considering the composition of interfacial cohesion,bond groove occlusion force and basalt fiber shear contribution force,and considering the influence of multi-bond groove uneven discount factor,interfacial agent(epoxy resin)and basalt fiber to provide reference for the calculation of shear bearing capacity of RPC-NC interface,and using the above-mentioned test data and post-simulation The above-mentioned experimental data and post-simulation data were used for verification. |
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