Massive concrete cracks are mainly caused by stress and constraints, and stress is an active factor. Constraint is a passive factor. The stress of mass concrete is mainly caused by changes in the environment temperature and humidity. Therefore, the environment temperature and humidity must be studied. For the effect of cracks on mass concrete, only the effect of ambient temperature and humidity on the stress of mass concrete needs to be studied. To this end, taking into account the main influencing factors - changes in ambient temperature and humidity, without considering the influence of gravity, layered pouring, and boundary constraints, the ideal spherical mass concrete is only generated under the influence of environmental temperature and humidity using a temperature and humidity recorder. Stress simulation and analysis.
In contrast, the spherical point is in contact with the surrounding air, ambient air temperature has a greater influence on the temperature of the spherical point, and the concrete pouring temperature is 25.3°C. If the pouring temperature is much higher than the ambient air temperature, the heat of hydration of the concrete itself is insufficient. To overcome the cooling of concrete, its temperature will quickly decrease; if the pouring temperature is close to the ambient air temperature, the concrete will suddenly rise slightly due to its own heat of hydration, and then the temperature will slowly decrease; if the pouring temperature is much lower than the ambient air temperature The air heat transfer, coupled with the hydration heat of the concrete itself, causes the temperature to rise sharply, and then its temperature slowly decreases. In general, from the analysis of the temperature and humidity recorder, it can be seen that the spherical point temperature quickly approaches the ambient temperature regardless of the temperature.
Because the spherical concrete body has a central symmetry, the concrete temperature is the same at the same distance from the center of the sphere, the center temperature is higher, and the outward temperature gradually decreases. The temperature history curve of spherical center point and spherical point under different temperature environment, due to the accumulation of large amount of hydration heat in the center, the concrete is also a poor conductor of heat, the heat accumulated in the center is not easy to dissipate outwards, and the ambient temperature does not easily affect the center point , so the center point temperature rises sharply.
Through the analysis of the temperature and humidity recorder in the experiment, it can be known that for different temperature environments, the maximum temperature difference first increases sharply, and the time for the maximum temperature difference is usually delayed by one day than the maximum temperature, and then gradually decreases. , but the rate of decrease gradually slows down. The surface “insulation method†can be used to delay the heat dissipation of the surface of the mass concrete, and to increase the ambient temperature in a disguised way, thereby reducing the temperature difference between the inside and outside of the concrete body. This explains the principle of the “heat preservation method†of the mass concrete surface from another angle.
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