Possibility of Thaumasite Formation in Marine Environments

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Title: Possibility of Thaumasite Formation in Marine Environments

Author(s): K. Yamada, M. Ichikawa, K. Honma, H. Hirao, and D. Mori

Publication: Special Publication

Volume: 234

Issue:

Appears on pages(s): 507-520

Keywords: carbonate; chloride; limestone; marine environment; seawater; sulfate; thaumasite

Date: 3/22/2006

Abstract:
In order to examine the possibility of thaumasite formation in concrete containing limestone powder and exposed to marine environments, immersion tests in artificial seawater, chloride and sulfate solutions at 5 & 20 °C were carried out as well as an exposure test in cold marine environments around 2.6 °C. From laboratory tests of 6 months compressive strength of mortar was found to decrease when immersed in chloride bearing solution. This was caused by an increase in porosity by the dissolution of Ca(OH)2. Although in sulfate solution no compressive strength decrease was observed even at 5 °C, thaumasite formation was detected in mortar containing limestone. However, after exposure in cold marine environment for 1.5 years, no degradation and no thaumasite formation was observed in seawater exposure. It is suggested that chloride ions suppress the formation of thaumasite to some degree.