Unexpected Expansion of Concrete Made with Laumontite Containing Aggregates Under Seawater Condition

Deterioration of steam-cured concrete specimens made with laumontite containingaggregates, under marine submerged, tidal, and atmospheric exposures for 30 years, wasinvestigated. The expansion of the specimens exposed to the marine submerged and tidalexposures ranged from complete disintegration to the moderate deterioration. Thedeteriorated regions contains little calcium hydroxide as well as calcium silicate hydrates,but rich with ettringite, brucite, and calcite. At the deteriorated region, white rim of ettringite crystal is found around the aggregates. Ettringite, brucite, and calcite are also found at the voids as well as along the cracked path. No visible crack was found on the surface of the atmospheric specimens. It is clearly understood that exposure condition is a governing factor related to the expansion caused by the laumontite mineral. No expansion of 30 years old atmospheric and tidal specimens is found after further wetting and drying exposure utilizing natural seawater of temperature 60oC.