Research On Preparation And Shrinkage Of Ultra High Performance Concrete

High-strength and high-performance concrete is a new type of cement-based composite material with high strength,excellent durability and workability,which is widely used in various large-scale construction projects.Its many advantages can significantly improve the performance of Prestressed Concrete Cylinder Pipe(PCCP).However,high-strength and high-performance concrete has the characteristics of greater self-shrinkage,which increases the risk of early maintenance cracking of the pipeline.This paper develops and prepares high-strength and high-performance concrete that meets the requirements of strength and durability of water pipelines.The shrinkage performance of high-strength and high-performance concrete was explored,and the finite element model of constrained shrinkage of high-strength and highperformance concrete was established to predict its early cracking situation in PCCP application and provide early warning for cracking of high-strength and highperformance concrete pipes,so as to take anti-cracking measures in advance.It mainly includes the following four parts:The basic components of high-strength and high-performance concrete for water pipelines were determined.Using the closest packing theory,we calculated the gradation of fine aggregate.Based on the maximum compaction theory and trial work,the mix ratio of high-strength and high-performance concrete was designed,and the preparation scheme and maintenance process of high-strength and high-performance concrete were determined.In order to verify that the high-strength and high-performance concrete prepared by the test meets the high-strength requirements,the compressive strength and splitting tensile strength tests of the high-strength and high-performance concrete cube were carried out with reference to the relevant regulations.The cubic compressive strength can reach 133.6MPa,and the splitting tensile strength is 8.33 Mpa.In today’s actual projects,PCCP mainly uses C40 concrete.Therefore,the strength of the UHPC prepared in this paper meets the characteristics of "high strength" and can meet the requirements of enhancing the strength of PCCP.The non-contact method was used to measure the shrinkage behavior of unconstrained high-strength and high-performance concrete under high temperature and normal temperature.The results show that the self-shrinkage behavior of highstrength and high-performance concrete under normal temperature curing environment is mainly concentrated in curing for 5 days,and the maximum shrinkage rate is 647.5;In the high-temperature curing environment,its self-shrinking behavior mainly occurs within 3 days of curing,with a maximum shrinkage rate of 790.45.A ring-constrained test under two environments of normal temperature and high temperature was designed.The strain collector was used to collect the compression strain of the inner steel ring during the curing process,and the average spontaneous tensile stress curve of the highstrength and high-performance concrete ring was derived.The numerical simulation analysis was carried out on the results of the ring-constrained specimen,and compared with the test results,the stress analysis method of the real pipe under the constraints of the internal model was established.The finite element model of the prestressed steel tube concrete pipe and mold with the same model as the actual project was established to explore the effect of shrinkage of high-strength and high-performance concrete in the manufacture of PCCP curing preparation.The prediction of the early cracking situation of high-strength highperformance concrete in PCCP application was realized,and the early cracking risk of high-strength high-performance concrete was reduced.