The storage houses provided for the cement should be such as will effectually preserve it from dampness, the floor being dry and strongly built. A circulation of air under the floor will insure dryness.
In building houses for storage, due regard should be given to the ease of getting the cement in and out, and facilities provided for the use of block and tackle in tiering.
When the cement is received, whether in sacks or barrels, it should, if possible, be so tiered in the warehouse that any package is accessible for sampling. In the case of barrels this may readily be attained by tiering in double rows, the barrels lying on the side. It has been found that ordinary cement barrels will withstand the pressure if tiered five high with a "binder" row on top; and when so piled, a warehouse 32 feet wide and 100 feet long will readily hold 2,200 barrels, an allowance of about one hundred fifty square feet of floor space for one hundred barrels.
232. Where storage space is limited, the barrels may be numbered and sampled before they are placed in the warehouse, and they may then be piled solid, but this should be avoided if practicable. Sacks cannot be quite so neatly stored, and since a smaller quantity is contained in a sack, they may be tiered so that every third or fourth sack is accessible. It is desirable where work is executed with the greatest care that every package be numbered for future identification, but this may sometimes prove impracticable, especially when the cement is in sacks, and in such cases the sampled packages only may receive numbers.
The amount of cement which shall be accepted on the test of a single sample must be determined by each user of cement according to his knowledge as to the uniformity and reliability of the brand in use, and according to the character of the work in which the cement is to be used. In a few isolated cases every barrel is tested, while sometimes several tons of cement are accepted on a single test. As the improvements in methods have decreased the work involved in making the simpler tests, the tendency has been to test a larger percentage of the packages.1
The report of the committee of the Amer. Soc. C. E. in 1885, contains the following concerning sampling: "There is no uniformity of practice among engineers as to the sampling of the cement to be tested, some testing every tenth barrel, others every fifth, and others still every barrel delivered. Usually, where cement has a good reputation, and is used in large masses, such as concrete in heavy foundations, or in the backing or hearting of thick walls, the testing of every fifth barrel seems to be sufficient; but in very important work, where the strength of each barrel may in great measure determine the strength of that portion of the work where it is used, or in the thin walls of sewers, etc., every barrel should be tested, one briquet being made from it".
The sample should be taken in such a manner as to fairly represent the package, and for this purpose a "sugar trier" may be used, by which is obtained a core of cement about one inch in diameter and eighteen inches long. As any tool used for boring cement barrels soon becomes dull, and as a sugar trier is somewhat difficult to sharpen, the . author prefers to use an ordinary bit and brace to penetrate the barrel head, and then extract the sample with a " trier," or a long, slender scoop of similar form provided with a handle.
For storing the sample until it is tested, it has been found convenient to use covered tin cans holding about one pint, the cover of the can being labeled with the number of the package from which the sample is taken.
1 In a paper read before the Institution of Civil Engineers in 1865-66, Mr. John Grant states that "after using, during the last six years, more than 70,000 tons of Portland cement, which has been submitted to about 15,000 tests, it can be confidently asserted that none of an inferior or dangerous character has been employed in any part of the work in question." (The Metropolitan Main Drainage, London.) This is an average of one test to twenty-five barrels.