Study On Mechanical Properties Of Glass Fiber Modified Recycled Concrete After High Temperature High Temperature

Recycled concrete is a new type of building material that uses recycled aggregates to replace part or all of natural aggregates.With the widespread use of recycled concrete technology in the field of building structures,its high temperature resistance is an important consideration in building structure design factor.In order to study the improvement effect of glass fiber on the high temperature performance of recycled concrete,the concrete with compressive strength grade of C30 was designed,288 cube specimens were made,normal temperature and high temperature tests were performed,and the test phenomena were observed,and then these specimens were subjected to high temperature The mechanical strength test preliminarily discussed the mechanism of glass fiber improving the mechanical properties of recycled concrete after high temperature.The main work and conclusions are as follows:(1)Through the physical performance test,compared with natural aggregate,the water absorption and crushing index of recycled aggregate have been increased by 3.85%and 5.23% respectively;the apparent density has been reduced by 3.94%.Then the glass fiber modified recycled concrete is designed for the mix ratio,and the final optimized design plan is as follows: the length of the glass fiber is 12 mm,the volume rate of the glass fiber content is 0%,0.3%,0.5%,0.7%;the mix ratio of the concrete is :Cement: Water: Sand: Stone=1:0.46:1.24:2.2.(2)Based on the above-mentioned mix ratio design scheme,a series of standard concrete cube specimens were produced and tested at room temperature and high temperature.The temperatures were selected as 20℃,200℃,400℃,and 600℃respectively.First,a comparative analysis of the appearance of glass fiber modified recycled concrete specimens after high temperature is found,and it is found that as the heating temperature continues to increase,the surface of the specimen changes from gray to light gray to white gray to muddy brown,and the degree of surface deterioration is Then gradually intensified.Subsequently,the relationship between the mass loss of each series of test pieces and the heating temperature was further studied.The experimental results showed that the incorporation of glass fiber can reduce the occurrence of cracks in the test piece;the mass loss gradually increased with the increase of heating temperature.In the process of 200℃～400℃,the mass loss rate is obviously increased.The incorporation of glass fiber can effectively reduce the quality loss of concrete under high temperature.(3)Carry out the compressive strength and splitting tensile strength tests of each series of concrete specimens after high temperature.Firstly,it can be seen from the failure form of the concrete specimens that the glass fiber can effectively inhibit the loosening and spalling of the concrete,and the integrity is better.Subsequently,the influence of heating temperature,replacement rate of recycled coarse aggregate,and fiber content on the strength performance of recycled concrete was further explored.The results show that with the gradual increase of heating temperature,the compressive strength and splitting tensile strength of concrete gradually decrease;the incorporation of glass fiber can enhance and improve the high temperature performance of recycled concrete to a certain extent.(4)Fit the experimental results to obtain the relationship between the strength performance of recycled concrete after high temperature and the heating temperature,which provides a reference for the engineering application of glass fiber recycled concrete after high temperature.