Abstract
Recently the utilization of sea-sand has been proposed because of the shortage of proper aggregates for reinforced concrete. In the case of sea-sand used as fine aggregate for reinforced concrete, there has been a question that the salt content in sea-sand accelerates the corrosion of steel. Steel bar surrounded by alkaline concrete is seldom subject to the corrosion, but in the case wherein the salt is contained in sand the corrosive action is quickened. As a result of comparative studies on the actions above mentioned and of experimental studies on special admixtures as inhibiter, the following conclusions have been drawn; (1) the salt content in sea-sand is actually very small owing to the dilution by rainfall or others, (2) allowable limit of salt content in sea-sand is 0.01% by weight for reinforced concrete, (3) in order to obtain the sea-sand with salt content less than 0.01%, it must be brought from the shallow depth of the beach at the distance of more than 30m from the seashore line, (4) for sea-sand with salt content more than 0.01%, it is effective to wash it away with clean water and, moreover, to use sodium nitrite (NaNO_2) as admixture in concrete, (5) the effects of sodium nitrite as inhibiter have been confirmed comparatively and electro-chemi-cally by means of the measurements of natural electrode potential, (6) no inferiority has been disclosed with respect to physical properties of sea-sand concrete when compared with usual concrete in which river-sand is used.
