To secure the best results, a mortar box should be provided for each 10 feet of width of street, and the full width of the street should be filled at practically the same time. After the filling has been carried forward for 40 or 50 feet, the same space should be filled again in like manner, except that the mixture for the second filling should be slightly thicker than the first. The joints should he filled en tirely to the top in the second application. After the joints have thus been filled, a half inch of fine sand should be spread over the entire surface of the pavement; and if the weather is very hot or dry, the sand should be sprinkled at intervals for two or three days, to insure that the cement does not lose by vaporization the water necessary for chemical combination in setting. Truffle should be kept off the pavement from seven to ten days, or at least until the cement has firmly set. If the cement filler is disturbed before it is fully set, it is practically no better than sand. If the cement filler is put in as described above and allowed to set firmly before being used, it will wear no faster than the best paving blocks and will prevent spilling and chipping of the bricks at the edges and corners.
The amount of grout required will vary with the openness of the joints, with the depth of the grooves (§ 728), and also with the quantity of sand of the cushion coat that works up into the lower part of the joints while the bricks are being rolled. With a 2-inch cushion and thorough rolling with a 5-ton roller, the sand will be forced up from to inch. With a grout mixed 1 to 1, a barrel of cement will fill from 25 to 40 square yards; and with a grout composed of 1 part cement and 1 of sand, a barrel will fill from 40 to 60 square yards.
If the grout is mixed in large quantities and dumped upon the pavement, it will require about one hour of labor for each 25 square yards. The cost of labor in applying the grout in small quantities as described in § 777 varies from 1 to 1.25 cents per square yard. The cost of the cement filler will depend upon the price of cement and the care employed in applying the grout. With ordinary re-pressed blocks and reasonable care in securing close joints, the cost of a 1 to 1 Portland-cement grout will usually vary from 8 to 12 cents per square yard. If the grout is dumped from the box
upon the pavement, the cost will probably be from 8 to 10 cents per square yard; but if it is mixed in small quantities and applied as described in the first paragraph of § 777, the cost will probably be 10 to 12 cents.
The advantage of the cement filler is that it protects the edges of the bricks from chipping, and thus adds to the durability of the pavement. When the joints are filled with sand or tar, the edges of the brick chip off, the upper faces wear round, the pave ment becomes rough, and the impact of the wheels in jolting over the surface tends to destroy the brick; while with a good cement filler, the edges do not chip, the whole surface of the pavement is a smooth mosaic over which the wheels roll without jolt or jar, and consequently the life of the pavement is materially increased.
An objection to the cement filler is that it does not take up the expansion of the pavement due to increase of temperature, and that consequently the pavement is likely to rise from the foundation and give out a rumbling noise as vehicles go over it. This rumbling can be eliminated by inserting special expansion joints as de scribed in § 786.
Another objection to the cement filler is that in making repairs it is difficult to remove the brick without breaking many, and it is difficult to clean the brick so that they may be used again. This is an advantage, if it will in any degree prevent the tearing up of the pavement; and at best this objection ought not to have much weight against durable construction.
A third objection is that the street can not be used while the cement is setting. Often the cement is not allowed to set fully before throwing the street open to traffic, and consequently the chief advantage of the rigid filler is lost.