A Treatise On The Principles And Practice Of Harbour Engineering

IIO HARBOUR ENGINEERING. Samples of the cement were taken from 2 per cent, to 5 per cent, of the barreis of every cargo. Extracts from the principal clauses of the spécification are as follows :— Chemical Analysis.—“If a sample of cement shows by chemical analysis that it contains either more than 1 per cent, of anhydrous sulphuric acid, or a trace of calcium sulphide, or more than 3 per cent, of magnesia, or more than 4 per cent, of ferrie oxide, or that the hydraulic index is less than 42, the cement shall be rejected.” Setting.—“ Cements which begin to set in less than one hour or finish setting in less than three hours or later than twelve hours, shall be rejected.” 'lensile Strength.—“The tensile strength of the neat cement briquettes after seven days shall be not less than 285 Ibs. per square inch, and after twenty-eight days not less than 500 Ibs. per square inch; that of the standard sand mortar briquettes after seven days shall be not less than 110 Ibs. per square inch, and after twenty-eight days not less than 215 Ibs. per square inch. (The standard sand mortar consists of 1 part of cement to 3 parts of standard sand.)” The sand was obtained at the mouth of the River Yamato; its grains were clean, sharp, and angular. The sand was screened before being°used, on a sieve of j^inch square meshes. No special variety of gravel was specified, but it was limited to that from sea beaches. It was obtained mostly from the north-western coast of Osaka Bay. The particles were hard and clean, but not very sharp. They were screened between 2-inch and f-inch sieves.