The Portland cement filler is prepared by mixing two parts of cement and one part of fine sand with sufficient water to make.a thin grout. The most convenient arrangement for preparing and dis tributing the grout is a water-tight wooden box carried on four wooden wheels about 12 inches in diameter. The box may be about 4 feet wide, 7 feet long, and 12 inches deep, furnished with a gate about 8 inches wide, in the rear end. The box should be mounted on the wheels with an inclination, so that the rear end is about4 inches lower than the front end.
The operation of placing the filler is as follows: The cement and sand are placed in the box, and sufficient water is added to make a thin grout. The box is located about 12 feet from the gutter, the end gate opened, and about 2.cubic feet of the grout allowed to flow out and run over the top of the brick (care being taken to stir the grout while it is being discharged). If the brick are very dry, the entire surface of the pavement should be thoroughly wet with a hose before applying the grout; if not, absorption of the water from the grout by the bricks will prevent adhesion between the bricks and the cement grout. The grout is swept into the joints by ordinary bass brooms. After about 100 feet in length of the pavement has been covered the box is returned to the starting-point, and the operation is repeated with a grout somewhat thicker than the first. If this second applica tion is not sufficient to fill the joints, the operation is repeated as often as may be necessary to fill them. If the grout has been made too thin, or the grade of the street is so great that the grout will not remain long enough in place to set, dry cement may be sprinkled over the joints and swept in. After the joints are completely filled and inspected, allowing three or four hours to intervene, the completed pavement should be covered with sand to a depth of about half an inch, and the roadway barricaded, and no traffic allowed on it for at least ten days.
The object of covering the pavement with sand is to prevent the grout from drying or settling too rapidly; hence, in dry and windy weather, it should be sprinkled from time to time. If coarse sand is employed in the grout, it will separate from the cement during the operation of filling the joints, with the result that many joints will be filled with sand and very little cement, while others will be filled with cement and little or no sand; thus there Will be many spots in the pave ment in which no bond is foimed between the bricks, and under the action of traffic these portions will quickly become defective.
The coal-tar filler is best applied by pouring the material from buckets, and brooming it into the joints with wire brooms. In order to fill the joints effectually, it must be used only when very hot. To secure this condition, a heating tank on wheels is necessary. It should have a capacity of at least five barrels, and be kept at a uniform tem perature all day. One man is necessary to feed the fire and draw the material into the buckets; another, to carry the buckets from the heat ing-tank to a third, who pours the material over the street. The latter
starts to pour in the center of the street, working backward toward the curb, and pouring a strip about two feet in width. A fourth man, with a wire broom, follows immediately after him, sweeping the stir phis material toward the pourer and in the direction of the curb. This method leaves the entire surface of the pavement covered with a thin coating of pitch, which should immediately be covered with a light coating of sand; the sand becomes imbedded in the pitch. Under the action of traffic, this thin coating is quickly worn away, leaving the surface of the bricks clean and smooth.
Tools Employed in Construction of Block Pavements. The principal tools required in constructing block pavements comprise hamsters and rummers of varying sizes and shapes, depending on the material and size of the blocks to be laid; also crowbars, sand. screens, anal rattan and wire brooms. Cobblestones, square blocks, and brick require different types of both hammers and rammers for adjusting them to place and forcing them to their seat. A cobblestone rammer, for example, is usually made of wood (generally locust) in the shape of a long truncated cone, banded with iron at top and bottom, weighing about 40 pounds, and having two handles, o,ne at the top and another on one side. A Belgian block rammer is slightly heavier, consisting of an upper part of wood set in a steel base; while a rammer for granite blocks is still heavier, comprising an iron base with cast-steel face, into which is set a locust plug with hickory handles. For laying brick, a wooden rammer shod with cast iron or steel and weighing about 27 pounds is used. A light rammer of about 20 pounds' weight, consist. ing of a metallic base attached to a long; slim wooden handle, is used for miscellaneous work, such as tamping in trenches, next to curbs, etc.
Concrete-Mixing Machine. Where large quantities of concrete are required, as in the foundations of improved pavements, concrete can be prepared more expeditiously and economically by the use of mechanical mixers, and the ingredients will be more thoroughly mixed, than by hand. Thorough incorporation of the ingredients is an essen tial element in the quality of a concrete. When mixed by hand, how ever, the incorporation is rarely complete, because it depends upon the proper manipulation of the hoe and shovel. The manipulation, although extremely simple, is rarely performed by the ordinary laborer unless he is constantly watched by the overseer.
Several varieties of concrete-mixing machines are in the market. A convenient portable type is illustrated in Fig. 60. The capacity of the mixers ranges from five to twenty cubic yards per hour, depending upon size, regularity with which the materials are supplied, speed, etc.
Gravel Heaters. Fig. 61 illustrates a device commonly employed for heating the gravel used for joint filling in stone-block pavements. These heaters are made in various sizes, a common size being 9 feet long, 5 feet wide, and 3 feet 9 inches high.
Melting Furnaces, for heating the pitch or tar for joint filling, are illustrated by Fig. 62. Various sizes are on the market.