Study On The Effect Of Polyethylene Fiber On The Properties Of Ultra-high Performance

Ultra High Performance Concrete(UHPC)is a cement-based composite material with ultra-high strength and excellent durability.It has been widely used in engineering,but its mechanical properties and preparation process need to be further optimized.In order to overcome the brittle failure of high performance concrete,further improve its tensile strength,enhance its toughness,in this paper,through test on Polyethylene fiber(Polyethylene fiber,PE fiber)on flow properties of ultra high performance concrete and the mechanical properties research,and from the aspects of preparation technology on the toughening effect of UHPC is optimized.The main contents are as follows:(1)Through fluidity test,compressive strength test,split tensile test,bending toughness test,three fiber lengths of 6mm,12 mm,18mm and 0.3%,0.5%,0.8%,1.0%,1.2%,1.5 %,2.0% of the seven kinds of volume content of PE fiber on the UHPC flow performance and mechanical properties,and through the scanning electron microscope test to observe the structure of PE fiber in the UHPC matrix,and finally determine the best PE fiber in UHPC Dosage and length.The experimental results show that the PE fiber with appropriate fiber length and volume content can significantly improve the toughness of UHPC,and maintain good flow performance and compressive strength.(2)Based on the existing preparation process of UHPC,the effects of admixture order,vibration mode and curing mode on the flow and mechanical properties of UHPC were studied.The experimental results of preparation technology study show that the order of mixing powder material and fiber first,then adding water and water-reducing agent can increase the compressive strength by 10.6%～11.9%,the splitting tensile strength by18.%～22.5%,and the initial cracking strength by 0.9%～2.3%.Stratified vibration can improve the compactness of UHPC,improve the compressive strength and splitting tensile strength,it has little effect on the initial crack strength,but it can make the total energy consumption in the process of crack development more,that is,better toughness.After curing for 7 days,compared with the normal temperature curing,the steam curing can increase the compressive strength of UHPC by 37.3%,but the splitting tensile strength and bending toughness decrease slightly.The splitting tensile strength decreases by 3.8%-5.7%,and the initial cracking strength decreases by 0.2%-2.3%.