混凝土抗冻技术.pptVIP

班级：水电2班 姓名：王大伟 学号：2012510197 混凝土抗冻理论及其应用 1 2 3 Basic Knowledge Causes of the Frost Damage Theory Application in Engineering Basic Knowledge 基础知识 Two types of frost damage Surface damage Inner damage Surface damage Damage caused by freeze thawing(冻融), acting on the surface of the concrete. Inner damage Inner damage shows no visible effects on the surface, but it would ultimately change concrete properties, such as elastic properties(弹性性质)。 Some Pictures Frozen Water and Unfrozen Water 可冻水与不可冻水 At a certain degree, only a part of the water content in concrete is Frozen Water. The additional volume produced by ice directly measures the freezing effect. The other part is condensate(凝结水), which is Unfrozen Water. Water distributed in the pore doesn’t freeze at the same time, but freeze gradually and orderly. The amount of the unfrozen water is the function of the porosity(孔隙率). The amount of the frozen water is reverse function of temperature. The pores of concrete incudes: 1.Gel pores(凝胶孔)2.Capillary pores(毛细孔）3.Air bubble(气泡) Causes of the Damage for Fresh Concrete 新拌混凝土的破坏原因 Fresh concrete has low intensity, high porosity, and high moisture content,(低强度，高孔隙率，高含水率) making it easier to receive frost heaving damage.(冻胀破坏) The freeze begins somewhere deep in the concrete in a big pore. Then the ice crystal grows by absorbing water from other pores. The internal tensile stress(内部应力)occurs in this process. When the process reaches a certain point, the concrete object breaks down. Causes of the Damage for Matured Concrete 成熟混凝土的破坏原因 Stage 1: Water freeze firstly appears in capillary pores(毛细孔), which produces water pressure of all directions and causes internal tensile stress(内部应力). Stage 2: The water crystal is formed in larger capillary pores and it continues to grow by absorbing water from other smaller capillary pores, which produces static stress(静应力). Material Climate The usage 材料的性质 Intensity(强度) Transformation(变形) Porosity(孔隙率) 气候条