Experimental Study On Static Fracture Of Concrete Under Pressure

Static crushing technology is an important supplement and development of explosive blasting technology.Compared with conventional explosive blasting technology,static crushing technology has no fly rocks,no vibration,no shock wave,no dust,no noise,no harmful substances in the construction process and other advantages.It has been widely used in the crushing of reinforced concrete,the directional mining of precious stones,the restoration of ancient buildings,the temporary support and removal of bridges and deep excavations.Based on the study of scholars at home and abroad,this paper studies the static fracture of reinforced concrete under the action of pressure.The hydration reaction rate,reaction temperature and volume expansion rate of static crusher were tested by 200mm x 200mm x 150mm temperature measurement device.Three kinds of water agent ratio(0.23,0.25,0.28)and three kinds of mixing temperature(25℃,35 ℃ 45 ℃)are used in this experiment.When the mixing temperature is constant,the water agent ratio has a great influence on the hydration reaction of the static breaker slurry.With the increase of the water agent ratio,the reaction time is more and more delayed.When the water agent ratio is constant,the increase of the mixing water temperature has a certain effect on accelerating of the earlier reaction time of the static breaker slurry and has little effect on the latter stage.For the three kinds of water agent ratio,the volume expansion rate is the maximum when the volume expansion rate is 4.4 times.By setting the three pressure and three water agent ratio,the three concrete specimens of size 200mm x 200mm x 200mm with different strength are burst tested.The results show that:The concrete blocks under pressure usually has 2-3 cracks.The crack extends to the minimum resistance line of the upper and lower stress surfaces of the test block.The smaller the pressure and water agent ratio is,the earlier the cracks come out.When the pressure is 4MPa and the water agent ratio is 0.23,the C30 concrete specimen has the largest crack whose width is 5.0mm.When the water agent ratio and pressure are the same,the time of the cracks come out in the concrete specimen will be delayed with the increase of the strength of the concrete specimen.The higher the strength is,the smaller the crack width is.Under the same water agent ratio,three kinds of static fracture test of concrete specimen under no pressure,which is free-standing concrete,are carried out.Through the comparison,it is conclude that the specimen cracking time is relatively early in the free state.The specimen generally produce 3-4 cracks.The direction of the crack propagation is randomly distributed in the direction of the minimum resistance line,and the final crack width is wide.When the water agent ratio is 0.23,the C30 concrete has a maximum width of 5.0cm.