To secure the best results, a mortar box should be provided for each 10 feet of width of the 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 be filled entirely 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 pave ment; and if the weather is very hot or the sand should be sprinkled at intervals for two or three days, to insure that the cement does not lose by vaporation the water necessary for chemical combination in setting. Traffic should be kept off the pavement from 7 to 10 days, or at least until the cement has firmly set. If the cement filler is dis turbed 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 bricks and will prevent spalling 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, 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 grout mixed 1 to 1, a barrel of cement will usually fill from 25 to 40 square yards. The cost of mixing the grout in small quantities and applying it as above varies from 1 to cents per square yard; and with ordinary repressed blocks and reasonable care in securing close joints, the cost of a 1 to 1 Portland-cement grout applied as described above will usually vary from 10 to 12 cents per square yard.
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 pave ment. When the joints 'are filled with sand or tar, the edges of the
bricks chip off, the upper faces wear round, the pavement 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 mosiac over which the wheels roll without jolt' or par, and consequently the life of the pavement is materially increased.
An objection to the cement filler is that it does not take up the ex pansion of the pavement due to increase of temperature, and that con sequently the pavement is likely to rise from the foundation and give out a rumbling noise as vehicles go over it. This rumbling can be pre vented by placing a tar-joint from to 1 inch thick next to each curb. The compression of the tar allows the bricks to expand without lifting the pavement from its foundation. This tar-joint can be inserted by setting a 1 inch board next to the curb before laying the bricks, and then after the bricks are laid withdrawing it and filling the space with coal-tar distillate No. 5 or 6. The longitudinal expansion can be taken up either by filling three or four transverse joints with tar, each 25 or 30 feet, or by inserting a 1 inch tar-joint each 40 or 50 feet. These expansion joints will require a gallon of tar for each 5 or 6 square yards.
An alleged 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 brick so that they may be used again. This is really 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 throw ing the street open to travel, and consequently the chief advantage of the rigid filler is lost.