Study On Green Ultra High Performance Concrete And Its Application In Subway Evacuation Platform

Ultra High Performance Concrete(UHPC)is a kind of cement-based material with ultra-high strength,ultra-high toughness and ultra-high durability,which is an ideal material in high durable engineering.However,the large-scale application of traditional UHPC is restricted by its high cost and processing difficulty.This paper focuses on the development of green UHPC material and its application,which,to a certain degree,provides technical support for the large-scale production and application of UHPC.This paper uses small-size coarse aggregate to prepare green UHPC,replacing cement with fly ash and limestone powder,and replacing quartz sand with river sand and mechanical sand.This paper studies on the influence of material composition on UHPC performance and studies on the development law of UHPC performance under different curing systems.It designs evacuation platform for green UHPC which simulates average people’s stress,strain and total deformation to the evacuation platform through Ansys,to make its structure and performance reasonable.The main study of this paper is as follows:(1)Studies on UHPC raw materials show that the addition of fly ash improves UHPC workability and reduces early strength,but improves later strength;a small amount of stone powder is conducive to the improvement of UHPC performance.When the content of stone powder is from 0.0%to 3.0%,the performances of works and mechanics are improved.When the content of stone powder is from 3.0%to 15.0%,the performances of works and mechanics are decrease;The machine-made sand and sand ratio affect the void ratio and compactness of UHPC.When the machine-made sand content is 15.0%,the performance of works and mechanics are the best;When the sand ratio is 44.0%,UHPC has good workability,high density and best mechanical properties;When the water-to-binder ratio is from 0.17 to 0.21,UHPC workability and mechanical properties meet the requirements;Steel fiber reduces UHPC work performance and improves mechanical properties.When the amount is 1.5%,the UHPC performance is the best;The green UHPC performs the best with the following ratio:water binder ratio accounts for 19%,fly ash content accounts for 20.0%,sand rate accounts for 44.0%,mechanical sand content accounts for 15.0%,limestone powder accounts for 3.0%,steel fiber volume accounts for 1.5%.(2)Studies on UHPC maintenance system show that the strength of UHPC is at the lowest under natural curing condition,and hot water curing and dry heat curing can improve the strength of UHPC in a short time.The increase of curing temperature can improve the compressive strength of UHPC.When the temperature of hot water curing ranges from 30℃to 80℃,the compressive strength increases and when the temperature of dry heat curing ranges from 100℃ to 300℃,the compressive strength increases.The curing humidity affects the compressive strength of UHPC,and the comprehensive strength can improve 6.5%compared standard water curing to no-wet curing.(3)The UHPC evacuation platform is prepared according to the optimal ratio.The panel size is 1190mm×850mm×50mm and the bracket size is 850mm×500mm×120mm.The concrete compressive strength is 138.2MPa,anti-bending strength is 16.6MPa.When it loads to the average standard of 5.0kN/m2,the analog value of slab deflection is 2.13mm,and the detection value is 2.26mm with a tiny difference of 5.8%.The analog value of bracket deflection is 1.64mm,and the detection value is 1.71mm with a tiny difference of 4.1%.So this 3D model matches the UHPC evacuation platform When the load reaches 13.1kN/m2,the evacuation platform is damaged.