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

本研究的主要目的是建立一个描述混凝土冻损机理的模型。本文在热力学的基础上，考虑硬化水泥浆体的微观结构，建立了硬化水泥浆体的理论模型。通过对不同含水率砂浆试件进行变形测量的一系列试验研究，验证了预测结果。结果表明，低温条件下砂浆的变形行为不仅受温度的影响，而且受含水率和微观结构的影响。同时，还对混凝土的温度和湿度条件随气候环境条件的变化进行了试验研究。三组混凝土样本暴露在一层建筑的屋顶上，其中一组用塑料屋顶覆盖，以避免雨雪。每组混凝土试件均由9个10Ox10Ox40O（mm）的棱镜组成，w/c=0.45或0.65。在四个面向北、南、东、西方向的棱镜的每个表面上的两个点测量温度。混凝土中的温度也在位于九个棱镜中心位置的棱镜上的三个点上测量。中心位置测点深度分别为距顶面10、100和200 mm。然后分析了混凝土温度随气候环境条件的变化规律，得出了经验公式。因此，最高气温是最高气温、白天平均风速和太阳总辐射的线性函数，而最低气温是最低气温、夜间平均风速和晴好天气指数的函数。最高和最低温度也随方向、混合比例和屋顶的存在而变化。在经验公式的基础上，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损风险。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