Study On The Performance Of Alkali-activated Slag ECC For Rapid Pavement Repair At Negative Temperture

With the rapid development of the economy,the requirement for the opening time of pavement repair is getting higher and higher,but the current rapid repair technology of pavement is mostly limited to the normal temperature environment.China has a vast territory and The construction time of more than 60% of the land area reaches 1/3 in winter.Therefore,it is very important to study repair materials that can achieve pavement repair in a negative temperature environment.In this paper,alkali-activated slag(AAS)is used as the matrix material and the negative temperature environment in the cold area is used as the starting point.For the alkali-excited slag mortar,there are problems of high brittleness and high shrinkage.Polyethylene fiber and steel fiber are blended to prepare Engineered Cementitious Composites(ECC).After the modification,the alkali-activated slag ECC(AAS-ECC)can be used as a rapid pavement repair material in the negative temperature environment of cold areas.This paper mainly studies the mechanical properties and shrinkage properties of AAS-ECC and AAS-ECC modified with steel fiber modified under different curing systems at-5℃ and-10℃.In addition,this paper calculates the reinforcement of the pavement repair layer according to the specifications.The results of uniaxial tensile experiments found that although the ultimate tensile strain value of AAS-ECC was high at the early age,the initial cracking strength and ultimate tensile strength were low.After adding 1% steel fiber,the tensile initial cracking strength and ultimate tensile strength increased by 60.6% and 56.5% respectively in the early age.The ultimate tensile strain decreased with the increase of the steel fiber content.The ultimate tensile strain of 1% steel fiber is 6%.Study the developmental rules of AAS-ECC shrinkage under different maintenance systems by using specific length instrument.The addition of PE fiber can effectively reduce the shrinkage value of AAS mortar.As the temperature decreases,the shrinkage value decreases.After pre-curing,the negative temperature AAS-ECC shrinkage value is only about 50% of the positive temperature curing.After pre-curing,put in negative temperature curing for 7d and 28 d,and then put in positive temperature curing,the AASECC shrinkage value will increase rapidly after turning to positive temperature.The shrinkage value of AAS-ECC modified with steel fiber is further reduced.The elastic modulus of steel fiber is large,which can construct a stronger system.Steel fibers can assist PE fibers to jointly withstand the load from the matrix,transfer the load of the cracked part to the uncracked matrix,and limit the development of cracks.The shrinkage of AAS-ECC with 1% steel fiber mixed at-5℃ and-10℃ under various curing systems is 23.6%-52.9%,11.9%-37.6% lower than that without steel fiber.According to the calculation of road continuous reinforcement in the road concrete design code,it is found that the longitudinal reinforcement ratio of 0.9% can effectively control the occurrence of initial cracks.In order to strengthen the connection between the repairing material and the old concrete in the surrounding area,the nails with a diameter of 20 mm are set on the side every 40 mm to prevent debonding.