Increased moisture content in concrete

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Increased moisture content in concrete

Post by agnes.ahlund » Thu Nov 02, 2023 1:15 am -1100

I have simulated a wall (outside -> in) with 100 mm brick, 30 mm air gap, 12 air changes per hour, 150 mm concrete, and 60 mm expanded perlite.
I'm experiencing an increased moisture content in the concrete, what could be causing this? I assume that the concrete is nearly diffusion-tight but that might not be correct. Could this be due to differences in vapor pressure?
Regards Agnes

Christian Bludau
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Re: Increased moisture content in concrete

Post by Christian Bludau » Mon Nov 06, 2023 4:12 am -1100

its not that easy to answer with that amount of information.
If it is a European location (cold in winter) I would guess, that the concrete is cold, there is a temperature gradient from inside to outside and so moisture from the room can pass the perlite insulation and condensates in concrete.
The diffusion resistance of the concrete is low, but it is not tight. If the drying of the concrete is slower than the uptake of moisture, there will be a long term increase of the concretes water content.
But also is dependent on the initial moisture of the concrete. If this is below the dynamic equilibrium moisture, the water content might increase for a long time.

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