Experimental Study On Influence Of Curing Temperature On Performance Of Shotcrete

The research was based on the background of the Gaoligong Mountain Tunnel,and the relevant experimental research and theoretical analysis of shotcrete performance under different curing temperatures were carried out.It is hoped to provide experimental basis and reference for the design and construction of shotcrete support under high ground temperature environment.The research contents and conclusions are as follows:（1）On the basis of preliminary design of shotcrete mix proportion,the experimental study of fly ash and basalt fiber content were respectively carried out.The optimum fly ash content of 15%and the basalt fiber of 2.4 kg·m^-3 were obtained.furthermore,the optimum proportion of shotcrete mix was determined.（2）Experimental study on physical and mechanical properties of shotcrete cured at 20℃30℃40℃and 50℃temperature showed that the apparent density of concrete was gradually increased,the water content and ultrasonic wave velocity gradually decreased with the increase of curing temperature.The early compressive strength of concrete increased gradually as the curing temperature rose,however,the compressive strength,splitting tensile strength and flexural strength of concrete decreased.（3）The study on uniaxial and conventional triaxial compression failure of shotcrete cured at 20℃,30℃,40℃and 50℃were carried out.The results showed that the constitutive relationship of the single axis failure of concrete at different curing temperatures is still in line with the Guozhenhai model;However,under conventional triaxial action,the axial compressive strength of concrete can be improved by the lateral restraint of confining pressure.The constitutive relations of triaxial compression failure of concrete cured at different temperatures are also established.（4）Based on the improved design of the bond strength test device,the bond strength between shotcrete（cured at 20℃30℃40℃and 50℃temperature）and rock was tested.It was found that the success rate greatly improved and the effect of the test error reduced by the improved design of the test device.And the bond strength between concrete and rock increased first and then decreased with the increase of curing temperature.（5）The durability test results of shotcrete at different curing temperatures showed that the carbonation resistance,permeability resistance and corrosion resistance of concrete decrease gradually with the increase of curing temperature.