252. Sand For Use In Sea Water

It has been said that granitic sands when used in sea water do not give good results on account of the felspar of the granite being attacked by the cement when the concrete is impregnated with sea water. M. Paul Alexandre would proscribe the use of argillaceous sands in sea water, but he found that sands containing calcareous marl gave excellent results in the sea, and others have stated that the mixture of crushed limestone with concrete has been known to hinder the action of sea water upon it. Since porous and permeable mortars are most liable to disintegration by sea water, it is evident that it is especially desirable to employ a sand in which the proportion of voids is small.