BRICK PAVEMENTS Characteristics of Brick Suitable for Paving. These are: (1) Not to be acted upon by acids.
(2) Not to absorb more than 1-600 of its weight of water in 4S hours.
(3) Not susceptible to polish.
(4) Rough to the touch, resembling fine sandpaper.
(5) To give a clear, ringing sound when struck together.
(6) When broken, to show a compact, uniform, close-grained, structure, free from air-holes and pebbles. ' (7) Not to scale, spall, or chip when quickly struck on the edges.
(8) Hard but not brittle.
Tests of Paving Brick. To ascertain the quality of paving brick, they are generally subjected to four tests, namely: (1) Abrasion by impact (commonly called the "Rattler" test); (2) absorption; (3) transverse or cross-breaking; (4) crushing. With a view to securing uniformity in the methods of making the above tests, the National Brick Manufacturers' Association has adopted and recommends the following: Rattler Test • 1. Dimensions of the Machin. The standard machine shall he 28 inches in diameter and 20 inches in length, measured inside the chamber.
Other machines may be used, varying in diameter between 26 and 30 inches, and in length between 18 and 24 inches; but if this is done, a record of it must be attached to the official report. Long rattlers may be cut up into sections of suitable length by the insertion of an iron diaphragm at the proper point.
2 Construction of the Machine. The barrel shall be supported on trunnions at either end; in no case shall a shaft pass through the rattling chamber. The cross-section of the barrel shall be a regular polygon having 14 sides. The heads shall be composed of gray cast iron, not chilled or case-hardened. The staves shall preferably be composed of steel plates, since cast-iron peans and ultimately breaks under the wearing action on the inside. There shall be a space of one fourth of an inch between the staves, for the escape of dust and small pieces of waste. Other machines may be used, having from twelve to sixteen staves; but if this is done, a record of it must be attached to the official report of the test.
3. Composition of the Charge. All tests must be executed on charges containing but one make of brick or block at a time. The charge shall consist of 9 paving blocks or 12 paving bricks, together with 300 pounds of shot made of ordinary machinery cast-iron. This shot shall be of two sizes, as described below; and the shot charge shall be composed one-fourth (75 pounds) of the larger size, and three fourths (225 pounds) of the smaller size.
4. Size of the Shot. The larger size shall weigh about 71 pounds and be about 21 inches square and 41, inches long,. with slightly round ed edges. The smaller size shall be cubes of 11- inches on a side, with rounded edges. The individual shot shall be replaced by new .ones when they have lost one-tenth of their original weight.
5. Revolutions of the Charge. The number of revolutions of a standard test shall be 1,800; and the speed of rotation shall not fall below 28 nor exceed 30 revolutions per minute. The belt-power shall be sufficient to rotate the rattler at the same speed, whether charged or empty.
6. Condition of the Charge. The bricks composing a charge shall be thoroughly dried before making the test.
7. Calculation of the Results. The loss shall be calculated in per cents of the weight of the dry brick composing the charge; and no result shall be considered as official unless it is the average of two distinct and complete tests made on separate charges of brick.
Absorption Test 1. The number of bricks for a standard test shall be five.
2. The test must be conducted on rattled brick. If none such are available, the whole brick must be broken in halves beforetreatment.
3. Dry the bricks for 48 hours at a temperature ranging from 230° to 250° F. before weighing for the official dry weight.
4. Soak for 48 hours completely immersed in pure water.
5. After soaking, and before weighing, the bricks must be wiped dry from surplus water.