Fundamental Study on Development of Methods for Evaluating Frost Damage Performance of Concrete

本文的主要目的是建立一个描述混凝土冻害机理的模型。在这项研究中，一个理论模型的基础上，热力学考虑到硬化水泥浆体的微观结构。通过对不同含水量的砂浆试件的变形测量，验证了预测结果的正确性。结果表明，砂浆在低温下的变形行为不仅受温度的影响，而且受含水量和微观结构的影响，同时，还对混凝土中的温度和水分条件作为气候环境条件的函数进行了试验研究。一组混凝土试件中的三组试件暴露在一层建筑物的屋顶上，其中一组试件覆盖有塑料屋顶以避免雨雪。每一组混凝土样本 ...更多信息 相同的混合比例（w/c=0.45或0.65）由9个10 × 10 × 40（mm）的棱柱组成。在四个棱镜的每个表面上的两个点测量温度，分别面向北、南、东、西四个方向。在混凝土中的温度也被测量在棱镜中的三个点位于九个棱镜的中心位置。在中心位置的测量点的深度为距顶面10、100和200 mm。然后分析了混凝土内部温度随气候环境条件变化的规律，建立了混凝土内部温度随气候环境条件变化的经验公式。最高气温与最高气温、白天平均风速和太阳总辐射呈线性关系，最低气温与最低气温、夜间平均风速和优良天气指数呈线性关系。最高和最低温度也随方向、配合比和屋面的存在而变化，根据经验公式计算了日本代表性城市的冻融循环次数，分析了混凝土结构的冻害风险。少

The main purpose of the present study is to make a model for describing the mechanism to cause the frost damage of concrete. In this study, a theoretical model was developed on the basis of thermodynamics by taking into consideration the microstructure of hardened cement paste. The predicted results were proved by a series of experimental study in which the deformation was measured for mortar specimens with different levels of water content. It was shown that the deformation behavior of mortar under low temperatures was influenced very much not only by the temperatures but by the water content and the microstructure.In the meanwhile, the temperature and moisture conditions in concrete was also experimentally studied as a fuction of the climatic environmental conditions. Three sets of a group of concrete specimens were exposed in the air on the roof of a first story building and one of them was covered with a plastic roof for avoiding rain and snow. Each set of concrete specimens of the … More same mix proportions (w/c=0.45 or 0.65) was composed of nine prisms of 10Ox10Ox40O(mm). Temperatures were measured at two points on each surface of four prisms facing to north, south, east and west directions. Temperatures in concrete were also measured at three points in the prism located in the central position among nine prisms. The depths of measuring points in the central position were 10, 100 and 200 mm from the top surface. Then the temperature in concrete was analyzed as a funtion of the climatic environmental conditions to formulate empirical formulae. As a result, the highest temperature was described as a linear fuction of the highest air temperature, the mean wind speed during daytime and the total solar radiation while the lowest temperature was given as a fuction of the lowest air temperature, the mean wind speed during night and the fine-weather index. The highest and lowest tempeeratures were also varied by the direction, the mixproportion and the existence of the roof.On the basis of the empirical formulae, the number of freeze and thawing cycles in representative cities in Japan was calculated and the risk of the frost damage of concrete structures was analysed. Less