Research On The Anti-freeze Critical Strength Of Low-temperature Concrete Influenced By Multi-factors

Concrete durability has been the focus of the field of civil construction materials. The researchers found that the durability was affected by the external factors in different degrees with the deepening of the study. The main factors can be briefly summarized as the southern corrosion and northern frozen according to the district. It is to prevent the corrosion reinforced of concrete in the hot and humid areas and to prevent the frozen of concrete in the cold regions. The loss in concrete produced in the frozen injury cann't be repair by the late standard curing and become the permanent loss for concrete durability. So it is the hot and difficulty of concrete research in northern regions to effectively aviod the infant frozen injury of concrete.Experts obtained the conclusion that the best method to prevent concrete frost injury is to improve the early concrete strength to critical strength before freezing, so how to determine the anti-freeze critical strength of different concrete have been becoming the important content in the low-temperature concrete construction areas. The anti-freeze critical strength of concrete is affected by three main factors. The three factors are the evaluation method, composition and Freezing condition.The anti-freeze critical strength of concrete was determined by the development of compressive strength of concrete after freezing in tradition. concrete attaches importance to the late durability in modern. Frost resistance evaluation methods is proposed in this paper on basis of the late durability of concrete. The anti-freeze critical strength was determined by this evalution method. The effect of this method is compared to the traditional method and the mechanism of evaltion method is analyzed. Results show that the anti-freeze critical strength of low-temperature concrete under frost resistance evaluation method is bigger than under compressive strenght evaluation method. The anti-freeze critical strength is same for part of concrete because of the cross of a variety of factors.The application of admixture in common low-temperature concrete is scare because of the low hydration activity in tradition. The effects of admixture composition on the compressive strength and the frost resistance property are researched in th paper. The anti-freeze critical strength is determined for different concrete which was added 10%,15%,20% of fly ash,5%, 8%,10% of Silica fume and double mixed 15% of fly ash and 5% of silica fume respectively. The mechanism of admixture in concrete is supposed as secondary aggregate and effect of the three groups by the analysis of pore structure. Results show that the concrete which added 15% of fly ash and 5% of silica fume has the best frost resistance property in any freezing environment.The research of anti-freeze critical strength in tradition was emphasis on the temperature factor of environment and ignored the effect of water. The research of anti-freeze critical strength in tradition was emphasis on the temperature factor of environment and ignored the effect of water. The freezing environment of concrete is setted as one air-frozen, one water-frozen and few frozens in this paper on general consideration of the effect of temperature and watre. The anti-freeze critical strength in different freezing environment is determined and the mechanism of freezing injury is analyse by the pore structure. Results show that the anti-freeze critical strength descending is one watre-frozen, few frozen and one air-frozen.The mechanism of two evaluation method is studied in this paper from the Changes in pressure area on the basis of macroeconomic performance effected by multi-factors with the pore structure and SEM of low-temperature concrete. The mechanism of admixture in concrete is supposed as secondary aggregate and effect of the three groups. The effect of freezing environment on the anti-freeze critical strength is analyse by the pore structure. The results provide the theoretical guidance and technical support for the winter construction by the determination of the anti-freeze critical strenth under multi-factors effect.