Unexpected expansion of concrete made with laumontite containing aggregates under seawater condition

Deterioration of steam-cured concrete specimens made with laumontite contained aggregates, under marine submerged, tidal, and atmospheric exposures for 30 years, was investigated. The expansion of the specimens exposed to the marine submerged and tidal exposures ranged from complete disintegration to moderate deterioration. The deteriorated 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. However, 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. Fortunately, the damage of real structures due to this special deterioration has not been clearly recognized in Japan, and other countries. However, the aggregate containing laumontite mineral is used for concrete fabrication, a careful quality control will be necessary.