Dear Colegues,
I am looking for information:
How the result of the measurement of air permeability of concrete depends on the temperature? Especially I am interested in correction factor for Autoclam test. I have found information, that it is enough to maintain a temperature above 5 degrees Celsius during the test.
However in:
http://www.rilem.org/docs/2015142902_0428-rilem-tc-psc-230-star-final-document-for-web-protege.pdf
there is correction factor according to ref [5].
Please enter a correction factor if any.
Best Regards,
Wojtek Kubissa
In my view, the following two mechanisms play a role: 1) Temperature causes the thermal expansion of the inter-structures of concrete, leading to the change of the existing pores in concrete; 2) Temperature also gives rise to the evaporation of moisture/water (existing as different forms) in the concrete, and subsequently changes the air permeability of concrete.
Hi Wojciech,
Enclosed I have you a comprehensive report: “Air permeability as characteristic parameter for the quality of cover concrete of concrete structures”. However, that is in German, the summary is in English and French. On page 10 is a summary of the measurement results: Typical water content and temperature of concrete.
Note: The water contents were derived from the specific electrical resistivity. The relationship between water content and specific electrical resistance was determined in the laboratory. The water content corresponds to the under usual practice conditions "mobile" water and was determined by 50 ° C-drying.
I hope, I could help you a little bit.
Much success
In my view, as temperature increases the air permeability of concrete decreases under normal temperature changes as the water inside the concrete would expand more than the concrete pore and hence block the way of the air. Hope that would help you
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