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对于浇筑后坍落度已经消失并开始有些凝固的混凝土,如果在适当的时期内再给予重复振捣,即所谓二次振捣,会给混凝土的强度、密实度等带来良好的影响,一般情况下可使强度增加10～20％。但是如果振捣时间失误,不但不会使强度增加,反而会造成不良后果。二次振捣可使混凝土强度增加,这一事实尽管很早以前就为人们所知道,但由于具体施工人员担心这样做会改变混凝土的凝结过程,破坏凝固中的水泥浆体结构,对成型质量造成不良影响,故在实际工程中很少应用。近年来,国外对二次振捣使混凝土强度增加的机理做了较深入的研究,对其适用范围和施工工艺等也做了一些研究改进,在实际工程中的应用也日渐增多。在此基础上,一些国家如日本等,已通过技术规范的形式规定把二次振捣做为混凝土的层间
For concrete after slump has disappeared and began to solidify, if given in the appropriate period of time to repeat the vibration, the so-called second vibration, will give a good impact on the concrete strength, density, etc. In this case, the strength can be increased by 10 to 20%. However, if the vibrating time is mistaken, it will not only increase the intensity, but will cause adverse consequences. The fact that the secondary vibrating can increase the strength of the concrete has been known to people for a long time. However, due to the specific construction personnel’s fear that doing so will change the concrete’s condensation process and destroy the cement slurry structure during solidification, the quality of the forming It is rarely used in practical projects due to its adverse effects. In recent years, foreign countries have conducted in-depth studies on the mechanism of the second vibration to increase the concrete strength, and have also made some research and improvement on the scope of application and construction techniques, and the application in practical projects has also increased. On this basis, some countries, such as Japan, have adopted the form of technical specifications to specify the second vibrator as a concrete layer.