The influence of temperature on water absorption in concrete during freezing

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Title: The influence of temperature on water absorption in concrete during freezing

Author(s): Tomas Sandström, Katja Fridh, Mats Emborg, Manouchehr Hassanzadeh

Publication: NCR

Volume: 45

Issue: 4

Appears on pages(s): 45-58

Keywords: Absorption, Temperature, Freeze/thaw, Durability, Hydropower concrete structures.

Date: 6/15/2012

Abstract:
A large part of the Nordic hydropower concrete structures are in direct contact with water and are therefore subjected to several transport mechanisms. External water can be transported into a porous material in three ways; by diffusion, capillary suction or by externally applied hydraulic pressure and all three mechanisms are active in a hydraulic structure. The presence of moisture is important in most destructive processes affecting the durability of porous construction materials The combination of water uptake and harsh climate in which most of the structures of the hydropower industry are situated, explain why damage due to freezing is common. Principally, the environment is a prerequisite for internal freezing to occur but also surface scaling has been found on these structures. Since there presently do not exist any analytical models that can describe the moisture transport for these specific situations of a hydraulic structure, a new test set up has been developed. The purpose is to study the possible effect of ambient temperature on water absorption properties of concrete. Thus, a test apparatus was constructed where bottom of concrete cylinder specimens of concrete could be placed in direct contact with water and the top was facing the ambient air with varying temperature. The results show that cycling the air temperature from +20 °C to -20 °C increases the water uptake compared to constant room temperature (+18 °C). With a constant temperature gradient (+2°C to -17°C) was the absorption found to be less, but since a large part of the specimens were frozen during a large part of the test, the absorption still was remarkable. Different parts of hydraulic structures are exposed to both of the climate conditions tested and an enhanced risk of frost damage exists.


Norwegian Concrete Association, International Partner Access.

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