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混凝土因其取材广泛、价格低廉、抗压强度高、可浇筑成各种形状,并且耐火性好、不易风化、养护费用低,成为当今世界建筑结构中使用最广泛的建筑材料。混凝土最主要的缺点是抗拉能力差,容易开裂。大量的工程实践和理论分析表明,几乎所有的混凝土构件均是带裂缝工作的,只是有些裂缝很细,甚至肉眼看不见(<0.05mm),一般对结构的使用无大的危害,可允许其存在;有些裂缝在使用荷载或外界因素的作用下,不断产生和扩展,使混凝土的强度和刚度受到削弱,耐久性降低,严重时甚至发生垮塌事故,危害结构的正常使用。我国现行公路、铁路、建筑、水利等部门设计规范均采用限制构件裂缝宽度的办法来保障混凝土结构的正常使用。以下所讨论的仅指后一类裂缝。
Due to its wide range of materials, low cost, high compressive strength, concrete can be poured into a variety of shapes, and good fire resistance, easy weathering, low maintenance costs, become the world’s most widely used architectural building materials. The main disadvantage of concrete is poor tensile strength, easy to crack. A large number of engineering practice and theoretical analysis show that almost all concrete members work with cracks, except that some of the cracks are very thin and even invisible to the naked eye (<0.05mm), and are generally not harmful to the use of the structure and allow Some cracks are continually produced and expanded under the action of load or external factors, thus weakening the strength and rigidity of concrete, reducing the durability, even causing collapse accidents in severe cases, and endangering the normal use of the structure. China’s current highway, railway, building, water conservancy and other departmental design specifications are used to limit the crack width of the components to protect the normal use of concrete structures. The following discussion refers only to the latter type of cracks.