Alkali-Silica Reactions in Concrete - Relationship between Water Content and Observed Damage on Structures

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Title: Alkali-Silica Reactions in Concrete - Relationship between Water Content and Observed Damage on Structures

Author(s): J. Lindgard, E. Rodum, and B. Pedersen

Publication: Special Publication

Volume: 234

Issue:

Appears on pages(s): 147-166

Keywords: alkali-silica reaction; damage; degree of capillary saturation (DCS); moisture

Date: 3/22/2006

Abstract:
Water is generally accepted to be one of the main factors affecting Alkali-Silica Reactions (ASR) in concrete. The water content in ASR affected structures is normally expressed as relative humidity (RH). However, the measurement of RH is notoriously very difficult and uncertain, particularly in the field. The degree of capillary saturation (DCS) may be a more suitable parameter to characterize the water content and the progress of damage on structures due to ASR. The relation between the RH in concrete and the DCS varies depending on several factors, where the water/binder-ratio is the most important one. For more than 100 Norwegian concrete structures the DCS has been determined on specimens cut from drilled concrete cores, according to a special procedure. The water content has been determined at depths in the range from about 100 to 400 mm from the surface, depth ranges where it is considered to be rather stable and uninfluenced by seasonal changes in the weather. The results show a good correlation between the presence of ASR in a concrete structure and the DCS. With only a few exceptions the degree of capillary saturation of the concretes with pronounced ASR is higher than 90 %. The extent of damages generally increases with increasing water content above this level.