Study On Crack Control And Application For Large Bulk Concrete

The feature of large bulk concrete is thick structure, large bulk, dense reinforcing steel bar, great pouring amount of once, long construction time, high request for construction technology, influenced by surroundings greatly. After pouring, because of large bulk, the heat of hydration and the gradient of temperature field of concrete are large, and the temperature of concrete is hot in inner and cold in outer, so it is easy to create crack.The main influencing factors of crack creation of various large bulk concrete are as following. First, structural crack is created by outer load; Second, material crack is created by temperature stress and contraction of concrete. At present, the focal point of study and construction control is crack of temperature.The crack of temperature often creates on the surface of large bulk concrete or the area of concrete structure where the change of temperature difference is large. The main mechanics is that, after pouring concrete, the hydration of concrete creates vast heat of hydration in the process of rigidification. Because of large bulk, the vast heat of hydration accumulate in the inner of concrete and emit difficultly, this lead to the temperature of inner is up fast. But the outer concrete emit quickly, so the temperature difference is large between outer and inner. Large temperature difference leads to the difference of expansion and contraction inner and outer of concrete, so the tension stress created on the surface of concrete. When the tension stress exceeds the limit of tensile strength, the crack is created on the surface of concrete. This kind of crack is often created anaphase construction. In addition, when the change of temperature is larger or the concrete is raided by cold wave in the process of construction, the temperature on the surface of concrete fall down rapidly, this lead to contraction. The contraction on the surface of concrete is inhibited by the outer, so large tension stress and the crack is created. General, this kind of crack is often created on the shallow extension of concrete surface.The crack control of large bulk concrete is mainly through following methods. One, material control of concrete. Through reduction the use level of cement and water, we can reduce the heat of hydration and avoid the crack...