A Treatise On The Principles And Practice Of Dock Engineering

117 CHAPTER IV. MATERIALS. Concrète — The Aggregate — The Matrix — Portland Cement — Its Finbness, Strength, Rate of Setting, and Soundness—Adultérants of Cement—Propor- tion oe Water— Action of Sea Water upon Concrète—Case of Disintegration at Aberdeen—Official Explanation and Possible Causes—Dr. Michaelis on Cement in Sea Water—Suggested Protectivb Mbasures—Practical Notes on Mining Concrète—STRENGTH OF CONCRETE— SAMPLE COMPOSITIONS—IrON AND Steel—Alloys with Manganese and Nickel—Impurities—Varieties of Cast Iron, Wrought Iron, and Steel—Defects in Manufactubed Iron—Spécifica- tions for Castings, Plates, and Bars—Working Strength—Tests —Weights- Corrosion of Iron and Steel—Effect of Sea Water on Dock Gates—Pre- servative Agents—Timber—Varieties used for Dock Work—Sélection of Timber —Destruction and Decay—Means of Préservation — Stone—Kinds Employbd —Destructive Agbncies. The dock engineer has to deal with a great variety of materials common to many other branches of constructive work, and the bulk of the informa- tion requisite for a thorough appréciation of their respective qualities and uses must naturally be sought in treatises dealing exclusively with such matters. At the same time, there are other materials not so commonly employed, and there are applications, adaptations, and standards peculiarly characteristic of dock work, and it is mainly with a view of treating these special features that the following notes have been compiled. In order to maintain some continuity of form, however, it will be necessary to touch upon each subject in its general aspect, but this will be done in the lightest possible manner, and details will be reserved for those questions more particularly germane to the province of maritime engineering. The materials selected will be dealt with in the following order : — Concrets. Timber. Iron and Steel. Stone. CONCRETE. Concrète is the term applied to an admixture of various mineral sub- stances which become incorporated into a solid body under chemical action. It consists essentially of two parts—the aggregate and the matrix. The aggregate is a heterogeneous mass of one or any number of the following materials: —Slag, shingle, burnt clay or earthenware, broken stone, broken brick, gravel and sand, mixed in varying proportions. The matrix consists of hydraulic lime or cement, combined with water.