Moisture Migration in Concrete Exposed to Freeze-T…

Author:MURu TIANWenling ZHOUMingjie(Schoolof… HebeiUniversityofTec… CivilEngineeringTech… Tianjin300401 China)

Unit:

Keyword:concrete durability freeze-thaw cycles moisture migration surface scaling

Classification:TU528

Year,volume(Issue):page number:2010,38(9):1713-1717

Summary:

A new interpretation of freeze-thaw deterioration of concrete is proposed.In the progress of freeze-thaw cycling,the water in some pores in concrete may be frozen,while others are unfrozen.Moisture flow from the unfrozen pores to the frozen pores occurs in each cycle driven by osmotic pressure and the difference in chemical energy between the ice and water.The moisture flow is a one-way process from smaller pores to larger pores because the water in larger pores has higher freezing point and freeze earlier than that in smaller pores.The pores near surface may suck up water from outside in the heating stage of freeze-thaw cycles owing to the vacuum caused by the decrease in volume of water when melted.After a number of freeze-thaw cycles,some larger pores become highly saturated,especially for larger pores near surface,and the pressure induced in the pores is very high in the later freeze-thaw cycles.The resultant tensile stress in the matrix around the larger pores may induce the cracking of the pore wall.Due to easily taking up water from outside,the pores in the surface layer of concrete specimens are much easier to be saturated than that in the interior,which leads to the severe cracking in surface layers and hence the surface scaling.The larger pores in the interior of specimens may be saturated and lead to cracking,which result in the decrease of relative dynamic elasticity modulus.

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References:

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