Study On Early Shrinkage And Temperature Deformation Of Hybrid Fiber RPC

Reactive Powder Concrete(RPC)is widely used in practical engineering due to its superior mechanical properties.However,RPC is easy to produce extremely high self-shrinkage.Once subjected to external constraints,the resulting residual tensile stress may cause early cracking.In addition,the curing of RPC will be affected by the actual temperature,resuliting in thermal expansion and conctraction deformation,and the hydration and heat release temperature of RPC is greater than that of ordinary concrete,so temperature cracking is more likely to occur than ordinary concrete.The cracking resistance of RPC at early age will affect the structual intergity and durability of concrete,so it is very important to analyze the shrinkage deformation and temperature deformation of RPC.In this paper,the effects of steel fiber and hybrid fiber(steel fiber-polypropylene fiber)on the free shrinkage and constrained shrinkage of reactive powder concrete during 0-28 days,and the effects of steel fiber and steel fiber-polypropylene fiber mixture on RPC compressive strength,splitting tensile strength and static elastic modulus were studied.The crack resistance of these RPC mixtures was evaluated based on the measured experimental dat.In addition,the temperature field and temperature stress of RPC mixture were analyzed by ABAQUS.The results show that:(1)The free shrinkage value and steel ring strain of RPC can be effectively reudced by adding steel fiber and hybrid fiber,and the crack emergence time can be significantly delayed.The effect of mixing steel fiber and polypropylene fiber RPC is the best.(2)The addition of steel fibers and hybrid fibers have a part to play in effectively reducing the maximum residual stress and stress relaxation of RPC,and the cracking risk of concrete mixed with steel fibers and polypropylene fibers was “low”according to the classification method of cracking cracking risk in ASTM C1581.(3)The hydration heat temperature,hydration heat release rate and hydration heat release rate of RPC can be increased by adding steel fiber and hybrid fiber,but the range is modest.No matter hydration heat temperature,hydration heat release or hydration heat release,RPC of hybrid fibers was slightly higher.In addition,adding fibers to RPC can reduce its temperature gradient.In general,adding fibers into RPC can improve its thermal conductivity.(4)Adding steel fiber and hybrid fiber to RPC can improve the equivalent age of RPC,but the improvement is limited.(5)The temperature stress of RPC ring was significantly reduced by adding steel fiber and hybrid fiber.The temperature stress of hybrid fiber RPC was slightly higher than that of SP20.