2008 年 47 巻 1 号 p. 25-33
This study aims to elucidate the alteration mechanism of mortar surface reacted with seawater and the relationship between characteristics of secondary products on the surface and salt concentration of seawater. The experiment was carried out in closed system using two kinds of mortars which were made from high-early-strength portland cement (HES) or alumina cement (AL) and silica sand, and two kinds of artificial seawater with half or twice of salt concentrations. Tablet type specimen (3.5-cm diameter, 1.0-cm height) was treated with seawater of 200.0 mL during 20 days. Results of the experiment showed that white products were crystallized on the surface of a tablet in each case. The products were characterized using SEM and XRD. In HES, petal shaped brucite, Mg(OH)_2, was produced by the reaction of portlandite, Ca(OH)_2, with Mg component in seawater. In AL, needle or column shaped aragonite, CaCO_3, was formed. Under high salt concentration of seawater crystalline size of brucite is relatively large in HES, production of aragonite are promoted.