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混凝土抗压强度随受热时间的变化

发布时间:2018/7/25 10:45:41 浏览次数:367

图5是应变率10-5/s条件下试块抗压强度与加热时间1H抗压强度之比,图5可知,高温混凝土强度为0h~3h,强度随PRO线性减小。加热时间的延长。这也表明混凝土的减少主要是在升温过程中,加热时间的影响低于加热温度的升高。在100℃时,试块抗压强度随着加热时间的延长而降低。


在300℃时,随着加热时间的增加,混凝土砌块的抗压强度逐渐降低。这是因为混凝土是一种热惰性材料。由于加热时间短,砌块内部温度升高,产生温度应力,试块抗压强度小,随着加热时间的增加,试块内部增加。温度的升高促进了未完成的水化反应,提高了试块的强度。在500℃时,压缩强度在300℃时降低,强度在2h后显著降低,然后放慢。其原因在于加热温度较高,提高了砌块内部温度,完成了未完成的水化反应,提高了试块的强度。


另外,随着加热时间的增加,块体中的水分不断逸出,减少了水化反应,降低了试块的强度。在两个因素的联合作用下,块体强度的变化表现为波[9 ]。当加热温度为700℃,加热时间为1h时,试块内的温度梯度产生裂纹,从而降低试样的强度。随着加热时间的延长,内外温差逐渐减小,温度应力降低,但试样内部温度增加了骨架在水泥浆中的结晶分解和压缩。强度急剧下降。因此,当加热时间为2h~3h时,在700℃时,强度下降比加热时间从1h增加到2h。


Fig。 5 is the ratio of the compressive strength of the test block to the 1H compressive strength of the heating time under the condition of strain rate 10-5/s。 From Figure 5, it is known that the strength of the high temperature concrete is 0h to 3h, and its strength decreases linearly with the prolongation of the heating time。 This also shows that the decrease of concrete is mainly in the process of temperature rising, and the effect of the heating time is lower than the increase of the heating temperature。 At 100 C, the compressive strength of test block decreased with the prolonging of heating time。


At 300 C, with the increase of heating time, the speed of compressive strength of concrete block gradually decreases. This is because the concrete is a hot inert material. Because of the short heating time, the internal temperature of the block is little increased, the temperature stress is produced, the compressive strength of the test block is reduced to a small extent; with the increase of the heating time, the inside of the test block is increased. The enhancement of temperature promotes the unfinished hydration reaction and enhances the strength of the test block. At 500 C, the trend of compression strength decreased at 300 degrees C, and the strength decreased greatly after the heat 2h, and then slowed down. The reason is that the heating temperature is higher, the inner temperature of the block is improved, and the unfinished hydration reaction can be completed, thus the strength of the test block is improved.


In addition, with the increase of the heating time, the moisture in the block is constantly escaping, reducing the hydration reaction and reducing the strength of the test block. Under the combined effect of two factors, the variation of the strength of the block shows a wave [9]. When the heating temperature is 700 C and the heating time is 1H, the temperature gradient in the test block produces a crack, which reduces the strength of the specimen. With the prolongation of the heating time, the internal and external temperature difference decreases gradually and the temperature stress decreases, but the internal temperature of the specimen increases the crystal decomposition and compression of the skeleton in the cement slurry. The intensity dropped sharply. Therefore, when the heating time is 2H ~ 3H at 700 C, the intensity decrease is greater than that of heating time from 1H to 2H.




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