The sand for a cushion should be clean and free from pebbles, which prevent the formation of a smooth bed, and possibly also cause the breaking of the bricks in ramming the surface.
When the sand cushion is I or 2 inches deep, an allowance of about half an inch is necessary for settle ment in driving the bricks to surface.
Laying the Brick. The bricks in a street pavement are usually laid on edge in courses across the street, each alternate course being begun with a half-brick to break joints in the courses. This is illustrated in Fig. 23, which represents a pavement as constructed for heavy traffic on concrete foundation.
In many cases the gutter-bricks are turned with the greatest dimension lengthwise of the street, with the object of facilitating the flow of surface-water in the gutter. The advantage of this is doubtful, as it has the effect of breaking the bond of the pavement between the gutter-bricks and roadway. This is shown in Fig. 24, which represents the construction of a double-layer pavement with brick and gravel base, as has been commonly used under light or moderate traffic.
In laying the bricks the men stand on the pavement already laid and, beginning at a curb, lay three or four courses across the street at once, the bricks being wheeled and piled on the edge of the finished work by laborers working continually in advance of the men laying. Wheeling over the newly laid bricks should be done on planks, to prevent driving the bricks out of surface. The courses may be kept straight and close together by driving back each block of eight or ten courses, a straight piece of plank four or five feet long being held by a handle on top against the side of the course of bricks and lightly struck with a small sledge.
After the bricks are laid across the street the end joints are tightened by forcing back each course with an iron bar, and closers are fitted into the end spaces. Considerable skill is required in this part of the work to quickly and accurately fit the closers without wasting the material.
Surfacing the Pavement. After the surface layer of bricks is in position it should be swept clean and rammed or rolled to a smooth and uniform surface. A five- or six-ton roller may be employed, passing three or four times over the surface, or a wooden rammer loaded with lead to a weight of 8o or no pounds may be used by striking upon a plank laid lengthwise of the street. The plank should be Io or 12 feet long by about a foot wide and 3 inches thick, and used only so long as it retains its form and solidity.
When the pavement has been brought to a surface a careful -inspection should be made and all defective or broken brick removed and replaced, a pair of brick tongs being used for the purpose, and all low bricks or low spots being raised and brought to surface. A straight-edge is desirable in determining surface, as the appearance is often deceptive to the eye, and a slight variation in color of brick is frequently mistaken for an irregularity of surface. Sometimes the pavement is sprinkled and soft bricks picked out by observing whether they hold moisture; this method should be used with caution and with full knowledge of the material, as sometimes a comparatively slight absorp tion will show quite markedly.