The Manufacture Of New Compound Additives For Shotcrete

In our country, shotcrete is an important shoring techanics in coal mine which has the virtues of simpleness, swiftness and economy. High rebound and dust are the technical problems urgently to be resolved in shotcreting in our country. Experiments inside and outside proved that additions mixed into shotcrete can enhance strength of shotcrete, save cement dosage, reducing material consume and markedly decrease dust and rebound.In this article, we prepared four types of shotcrete additions in the body of Portland cement, Through testing net cement coagulating time and cement strength, we characterized the effect of the materials in the course of cement hydrating and vulcanizing and the contribution of the materials in reducing rebound and dust. We vote bentonite addition to study more, and analyze the effect of material dosages , temperature, the ratio between water and ash, cement breeds on cement hydrating and vulcanizing. And in assistant of the microcosmic testing of SEM and IR, we discussed the physical and chemical changes of the addition in the course of cement hydrating and its mechanism in reducing rebound and dust.The study results indicated that, when the ratio between water and ash is 0.4, the new addition can make the net cement start to coagulate early in 3 min and coagulate eventually in 10 min, and the strength of 1d, 3d, 28d are 9.13MPa, 17.77MPa, 28.42MPa. The strength ratio of 28d is 91.1% and the strength loss are less than 10%, which meet the nation's criterion of first rank addition. The local test in Yunhe and Yangcheng coal mine of Jining Mining Group Corp. proved that the new shotcrete addition excelled J-85 accelerator in decreasing dust and reducing dust. It can decrease dust 11.4% and reduce rebound 30.5%. The addition has desired capability and wider application perspective.Through SEM and IR microcosmical testing, we discussed the action mechanism of the new addition. The net cement with bentonite can form hydrogen key which can improve the felt of the systematic and are well for eventual strength; The main mechanism of J-85 accelerator to accelerate concrete coagulating are in alkalescent condition to make aluminate and gypsum link and block the building of calcium and aluminium sulphate around cement granule; Polypropylene acid can improve early strength of cement through altering the thickness of hydroxide in cement grout. The new addition can impel the cement hydration to the core, and affect the development of eventual strength through the building of calcium and aluminium sulphate.