Research On Steel Fiber Reinforced High Performance Concrete Prepared By Joule Curing At Ultra Low Temperature

At the beginning of 2018,China put forward a white paper titled "China’s Arctic Plan",which clearly pointed out that actively developing Arctic resources is of great significance to China’s military and economic development.To actively implement the Arctic strategy,infrastructure construction in the Arctic region is indispensable.High performance concrete structure is a cement-based material with high strength and excellent durability,and the low thermal conductivity of cement-based material can ensure that HPC is suitable for application in polar regions and other cold regions.However,the current concrete construction method cannot realize the on-site construction of cement-based materials in polar regions and other extremely cold regions,which hinders the deployment of major strategies in China.Therefore,Joule curing,a new type of concrete structure curing method,has been proposed in this paper.The heat generated in the curing process of Joule curing method was used to realize the on-site construction of concrete structure in negative temperature environment.This paper mainly focused on the material composition of high performance concrete structure,studied the performance development law of Joule curing specimen under different ambient temperatures,and clarified the evolution law of impact resistance and heat performance of specimens prepared under negative temperature conditions.The performance of Joule curing prepared steel fiber reinforced HPC was modified by graphene nanosheets.The main research contents and achievements of this paper include:The theoretical prediction of conductive percolation threshold of steel fiber in the matrix was realized by cellular automata algorithm,and the experimental method was used to further determine the optimal content of steel fiber,and the simulation results were predicted.The experimental results showed that the conductive percolation threshold of steel fiber in the matrix was 2.5vol %.At the same time,the influence of factors including silica fume content,fine aggregate gradation,water-binder ratio and preparation process on the structural properties of Joule curing prepared high performance concrete was studied,and the optimal mix ratio of steel fiber reinforced high performance concrete was determined.The performance development law of steel fiber reinforced high performance concrete under Joule curing at different ambient temperatures(-20 ℃,-30 ℃,-40 ℃,-50 ℃ and-60 ℃)was studied.The specimens were prepared by gradient temperature Joule curing method,and the mechanical properties and microstructure evolution of specimens were further studied.The effect mechanism of Joule curing on high performance concrete structure under different ambient temperature was clarified,and the effect of environmental factors on specimen performance was judged.Results showed that the compressive strengths of specimens could meet the requirements of HPC under various negative temperature conditions,reaching the strength range of 70.7 MPa～78.5 MPa,which effectively promoted the strength formation of HPC under cold environment.The dynamic mechanical properties of high performance concrete cured by Joule curing under different ambient temperatures were studied,and it was determined that high performance concrete structure prepared on site in negative temperature environment had good impact resistance,the DIF value of the sample cured at-40 ℃ was large than 1.45,which was suitable for polar deployment construction in polar regions.At the same time,the heat condition of high performance concrete under Joule curing was modeled and predicted to judge the influence of different factors on the heat performance of specimens,and it was found that the electric power of 25 W was enough to improve the curing temperatures of the samples cured at the range of-20 ℃～-40 ℃,which can improve the strength formation of the sample,and realize the guide for the Joule curing process.Two-dimensional graphene nanoplatelets were utilized for the modification of steel fiber reinforced high performance concrete,and the constant power Joule curing method was used for the preparation of specimen under-20 ℃,aiming at studying the effect of different dosages of graphene promotion effect on the properties of steel fiber reinforced high performance concrete cured by Joule curing.Further,the development regularity of Joule curing prepared specimen was clarified,and the results showed that under the dual action of Joule curing and graphene,the mechanical properties of specimens can be improved by more than 20%.