Research On The Amti-freeze Critical And Early Maturity Of Negative Temperature Concrete In -10℃ Condition

The damage of concrete caused by early age frost usually tends to be nonrecoverable in Winter construction. The concrete often can’t reach its design strength after curing for a certain age at normal temperature, at the same time, its durability reduced greatly. An important factor for negative temperature concrete to resist early frost damage is ensure its strength reached resistant freezing critical strength before frost. Studies on critical strength of negative temperature concrete before concern a little influence factors and have little consideration about i ts durability in the late period.This paper mainly studies the critical strength of different strength concrete(C30,C40,C50)under certain condition,concerning adding anti- freezing admixture or not and different frost negative temperatures(-5℃,-10℃,-15℃). As well as the frost resistance and impermeability of negative temperature concrete which has reach its critical strength at the later period were studied.Research shows that, the critical strength of concrete without antifreeze is not a constant value. Resistant freezing critical strength grows with the growth of strength grade of concrete. The lower environmenta l temperature is, the higher critical strength the concrete needs. As to the concrete with antifreeze, there is no obvious regularity between the critical strength and different strength grades or different frost temperatures. Antifreeze can not only shorten the procuring age, but also reduce the critical strength.The strength loss rate in later period of negative temperature concrete which has reached critical strength is less than 5%, but the frost resistance lose rate is over 5%, at the same time, the impermeability suffer different degrees of damage co MPared with the control group which is in the standard curing condition. The later durability of negative temperature concrete is not satis factory. Negative temperature concrete with durability require ment should extend its procuring age according to the project construction situation.In order to avoid or minimize the damage of early frost to concrete, not only to take advantage of early detection methods to understand the extent of frost damage to concrete, and more should be aware of early frost damage to concrete developments affect of the microstructure and early internal microstructure. So we can deepen the understanding of the negative temperature concrete.We change preparing the maintenance time, intensity levels and types of antifreeze, and observe the change rule of early frost on the microstructure and the late strength of concrete at different times of maintenance. In preparing the maintenance time, intensity levels and types of antifreeze, through using method of loss of weight, mercury porosimetry analyzer and interface zone micro hardness tester, we qualitative analys the degree of hydration, the pore structure and microhardness.