PORTLAND CEMENT concrete is the mass formed by mixing Portland cement, sand, gravel (or particles of other suitable materials), and water.
The quality of concrete may be made to conform to certain requirements which vary with the purpose of the structure in which the material is to be used; economy, strength, water-tightness, fire resistance, or resistance to wear and shock may be the chief requisite. The character of the constituent materials, the proportions in which they are used, the consistency, the method of mixing, and the placing and curing of the concrete are important factors in securing the desired qualities of the finished product.
Total failure or a product which does not give the service expected is often the result of the nonobservance of practices recognized as necessary in the preparation and use of concrete. This bulletin is intended to assist the inexperienced in making and using concrete suitable for general farm construction and is confined to a discussion of the rudiments of plain (not reinforced) concrete work.
[MATERIALS.]
CEMENT.
Portland cement is used because it is the only kind adapted to general construction. Other cements are manufactured but they possess individual characteristics that restrict their use. The word Portland is not a trade name, but signifies the kind and distinguishes it from the slag, natural, and other cements.
A number of brands of Portland cement are manufactured, most of which are made to meet the requirements of a fixed standard adopted by the United States Government and the American Society for Testing Materials. Cement always should be tested for use in important work, but this is impractical for the user of small amounts and it is generally safe practice to omit the test if a reliable brand of Portland cement of American manufacture is selected, especially if the dealer's or manufacturer's guaranty that it meets the standard is secured.
The following simple test for soundness is easily made and is on the side of caution. Make a ball, about 11/2 inches in diameter, if neat cement and water; place it under a wet cloth and keep it moist for 24 hours, then put the ball in a vessel of water; allow the water to come to the boiling point slowly and to boil for 3 hours. A good cement will not be affected, but an inferior one will check, crack, or go to pieces entirely.