The Technology Research On Low Rebound Loss Spray Concrete

With the rapid development of the national highway tunnels, subway and underground engineering, the amount of shotcrete shows a sharp growth, but due to the current shotcrete high rebound rate, not only cause a huge waste of material and construction of low efficiency, but also have some impact on the quality of the project and the natural environment.So the study of low rebound shotcrete technology has great significance..Studies on low rebound shotcrete technology were made in several aspects as bellow.1.In the mix design, change cohesiveness and workability of shotcrete through introduction of superfine mineral admixture or rebound suppress materials,so as to achieve lower spring rate of sprayed concrete. The influence of superfine mineral admixture and rebound suppress materials on evaluation of shotcrete was studied, and the influence of superfine mineral admixture and rebound suppress material on mortar yield stress was studied useing cement mortar mixer test.2. A series of image of the shotcrete such as jet characteristics,jet velocity and diffusion angle of shotcrete were studied. In view of the sprayed concrete jet characteristic,a rebound model was built up and rebound mechanism of sprayed concrete was analyzed.3. Variation of rebound rate and injection conditions(injection distance, working pressure, the injection angle) with injection condition were analyzed by means of outdoor injection experiments, the optimum pressure-feeding pressure, spray distance and spray angle were obtained.4. The effect on reducing rebound rate by mixing three kinds of mineral admixtures and rebound suppress materials was test checked.It may give a theory basis to the composition design and operating methods of the tunnel shotcrete project..