Study On Preparation And Properties Of Ultra High Performance Concrete

Ultra High Performance concrete(UHPC)is a kind of special concrete with super durability and super strength.In practical engineering applications,since concrete cracking is unavoidable,compared with ordinary concrete,toughness and crack resistance of UHPC is greatly improved.UHPC also has excellent structural stability even in a special environment.In this paper,the mixture ratio of fine aggregate UHPC was designed based on the theory of compact packing,and the effects of different steel fiber dosage,shrinkage reducer dosage and expansion agent dosage on the working performance,mechanical properties,volume stability and corrosion performance of fine aggregate UHPC were studied.At the same time,the mixing ratio design of UHPC with coarse aggregate was studied,and the effects of different steel fiber content on the working performance,mechanical performance and thermal performance of coarse aggregate UHPC were investigated.Specific research results are as follows:(1)For the working performance of fine aggregate UHPC,the use of steel fiber,shrinkage reducer and expansion agent will lead to the decrease of the fluidity of fine aggregate UHPC,and the fluidity decreases with the increase of the their dosage.(2)For the mechanical properties of fine aggregate UHPC,steel fiber can improve the compressive strength and flexural strength,and the two strengths increase with the increase of the dosage of steel fiber.The use of shrinkage reducing agent and expansion agent will decrease the compressive strength and flexural strength,and the more the dosage of shrinkage reducing agent and expansion agent,the compressive strength and flexural strength will decrease more obviously.(3)For the volume stability of fine aggregate UHPC,the use of shrinkage reducer and expansion agent can inhibit the volume shrinkage phenomenon.When the dosage of shrinkage reducer is in the range of 3% to 7%,the volume shrinkage inhibition effect is more obvious.When the content of expansion agent is in the range of 8% to 12%,the volume shrinkage of UHPC can be also improved.When the content of expansion agent is8%,the UHPC has almost no shrinkage and the volume stability is the best.When the expansion agent content is more than 10%,fine aggregate UHPC has a slight expansion effect.(4)Compared with the reference sample,the reinforcement corrosion of fine aggregate UHPC is lighter in the sample with 3% shrinkage reducing agent.The reinforcement corrosion of the sample with 5% shrinkage reducing agent is serious.The reinforcement corrosion of the sample mixed with 8% expansion agent is lighter,but the reinforcement corrosion of the sample mixed with 10% expansion agent is intensified.It shows that there is no obvious linear relation between the content of shrinkage reducer and expansion agent and the corrosion property of steel bar.(5)For UHPC mixed with coarse aggregate,steel fiber will reduce its fluidity and decrease with the increase of the dosage.For mechanical properties,the compressive strength and splitting tensile strength increase with the increase of dosage.For thermal performance,steel fiber will improve thermal conductivity and reduce thermal insulation performance.And the more steel fiber content,the higher the thermal conductivity.Considering the working performance,mechanical performance and thermal performance,it is suggested that the optimal dosage of steel fiber in coarse aggregate UHPC is 1.5%.Figure [83] Table[20] Reference[71]...