عنوان مقاله [English]
Stress gain of concrete is a heated procedure. The amount of heat is significantly depends on cement type, cement content and cement-water ratio. While the rate of generated heat is far more than the rate of heat transfer to exterior part of concrete mass, temperature in interior part of concrete element during that procedure increases. Furthermore, the strength gain of concrete is function of temperature history of every part of element which is influenced by heat caused by hydration. If the stress generated by heat in fresh concrete is more than acquired strength of concrete, then early cracks will be occurred in the concrete mass. As a result, thermal analysis and checking the strength gain in massive concrete structures like concrete dams, foundations and bridge decks would be especially important. The terms heat transfer and thermal analysis are composed of some mechanisms. In this paper we model the mechanism and simulate the strength gain of concrete by finite element method. After verifying the finite element model, we will study the strength gain of a concrete slab and a reinforced concrete beam. All the experiments are in accordance with ASTM standard to determine the parameters of cement heating procedure. Controlled environment with constant temperature is used for curing of concrete specimens. Six different ages (first age for about 4 MPa compressive strength and next ages are twice the previous age. The specimens are studied in three different temperatures, 15 ºC, 25 ºC and 35 ºC and in total, 54 specimens are considered. The results show that this numerical method can estimate the heat transfer in the concrete body with acceptable accuracy. In addition, the results exhibit this fact that the proposed time for removal of forms in the ninth part of national building regulation of Iran “design and construction of concrete structures” should be considered with more details.