Relative Humidity Measured by Wooden Stick Method in Concrete Structures: Long Term Measurements and Reduction of Humidity by Surface Treatment

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Title: Relative Humidity Measured by Wooden Stick Method in Concrete Structures: Long Term Measurements and Reduction of Humidity by Surface Treatment

Author(s): V. Jensen

Publication: Special Publication

Volume: 212

Issue:

Appears on pages(s): 621-636

Keywords: alkali aggregate reaction; concrete; relative humidity; silane; surface treatment; wooden stick method

Date: 6/1/2003

Abstract:
Measurements of relative humidity (RH) by means of wooden sticks of the species Ramin (Gonystylus macrophyllum) have been used in Norway since 1995. The method is especially applicable to concrete with high internal humidity as in structures damaged by Alkali Aggregate Reaction (AAR) or freezing and thawing. Results up to now show that the relative humidity is stable 5 cm from the surface and that ingress of rainwater is an important Source of water in most of the outdoor exposed concrete structures. Correlation tests have shown that wooden sticks still are in good condition and reliable after 7 years continuous use. Measurements on surface treated columns and beams in two structures show that the relative humidity 5-cm from the surface decreased significantly during four years monitoring, which was not the case in untreated concrete. It is concluded that surface treatment is able to reduce the relative humidity in concrete structures exposed to rainwater.