Experimental Study On Reducing The Rebound Rate Of Machined Sand Wet Shotcrete In Highway Tunnel

With the application of wet-blasted concrete technology in highway tunnels,the problem of high rebound rate of wet sandblasted concrete using mechanism sand still exists.Many scholars have done research on reducing the rebound rate of wet-sprayed concrete,but considering accelerators and reductions.The effect of water agent on the rebound rate of mechanical sand concrete is insufficient.In this paper,combined with the Hangzhou Shaoxing Taizhou Pingshui Tunnel Project,the experimental research on reducing the rebound rate of the mechanism sand wet spray concrete will be carried out for these shortcomings and relevant conclusions will be drawn.(1)Experimental study on the effect of different dosage accelerators and water reducers on the rebound rate of mechanical sand concrete.The test found that when the amount of accelerator was low,the effect of promoting coagulation was not obvious.When the amount of quick-setting agent was high,the concrete was tuberculous.In both cases,the rebound rate was large and the long-term strength was also affected.When the amount of water reducing agent is small,the concrete slump is small.When the amount of water reducing agent is high,the concrete is fluid and the rebound rate is high.The amount of accelerator and water reducer is optimized by the law of rebound rate change.(2)The experiment of using stone into the mortar layer simulates the process of penetration of coarse aggregate into the concrete in wet spraying.The experiment found that when the stone particles are small,the injection speed is appropriately increased,and when the stone particles are large,the ejection speed is appropriately lowered,and the rebound rate can be lowered.First,a mortar layer of appropriate thickness is sprayed on the excavated rock surface,and the construction step of spraying the concrete can also reduce the rebound rate.By adjusting the ratio of the quick-setting agent and the water reducer in the sand concrete,changing the injection speed or changing the construction steps of the wet-spray concrete,the rebound rate can be reduced,the cost can be saved and the construction period can be shortened.It provides reference value for in-depth study of wet spray concrete materials and construction technology.