Experimental Study On The Improvement Of Flexural Behavior Of Rectangular Beams By UHPC With High Flow State

In recent years,ultra-high performance concrete(UHPC)has gradually been applied to many fields of civil engineering due to its ultra-high compressive strength and extremely excellent durability.This paper first studies the working performance,mechanical properties and durability of UHPC.On this basis,a flexural test of one Normal Concrete(NC)beam and 8 U-NC beams is designed,and the resistance of the test beam is studied.Flexural capacity and deformation characteristics.The work and conclusions made in this article are as follows:(1)The working performance of UHPC is one of the key factors for the construction quality of composite beams.The water-binder ratio has a significant effect on the fluidity and compressive strength of UHPC,and the steel fiber content has a significant effect on the flexural strength of UHPC.The preparation of UHPC is based on the principle of maximum compaction.The tight packing of various components and quartz sand is the key to ensuring UHPC's ultra-high mechanical properties.The recommended ratio of sand to rubber is about 1.15 and the amount of silica fume is about 25%.The content of fly ash is 15%,and the content of steel fiber is about 1.5%.Too small water-binder ratio is not conducive to the discharge of gas,and it is easy to form pores.It is recommended that the water-binder ratio be about 0.18.(2)The electrical flux of UHPC150 is lower than that of C40 concrete by two orders of magnitude,which greatly improves the resistance to chloride ion penetration and can effectively improve the durability of U-NC beams.Hot water curing helps reduce the drying shrinkage of UHPC150,making C40 and UHPC150 have similar shrinking trends,which provides a prerequisite for better cooperative work after pouring.(3)The normal strain distribution of U-NC beam mid-span concrete basically conforms to the assumption of flat section,and the two materials have good flexural performance,which provides experimental support for the analysis of U-NC beam flexural performance.Compared with the NC beam,the U-NC beam has the largest increase in cracking load,and has a greater increase in yield load and ultimate load.The steel fiber content is 1.5%,and the UHPC replacement height is 125 mm.This is a better combination of U-NC beam.the way.(4)The theoretical calculation model of the U-NC beam's normal section flexural bearing capacity is established.On the basis of considering the contribution of the UHPC's tensile effect to its flexural bearing capacity,the U-NC beam's normal section flexural resistance is proposed The calculation formula of the ultimate bearing capacity,the calculated value is in good agreement with the measured value,and the tensile impact coefficient value suitable for U-NC beam is 0.5.By analyzing the ductility of the U-NC beam,it can be seen that the favorable seismic design is matched with a larger UHPC to replace the height and steel fiber content and a smaller reinforcement ratio.