Cement Sidewalks

Transverse Slope.

A cement walk when built along the side of a street should have a transverse slope of at least * of an inch per foot, and preferably 3 or of an inch; but should never have more than f of an inch per foot. A slope of * an inch per foot gives an unpleasing appearance, and, when the walk is icy, pedes trians slide toward the gutter, particularly on a windy day.

When the walk is laid on comparatively level ground in a public park or on private grounds, it should be crowned to drain the surface. If the center is raised jE to of an inch per foot of half width, the surface will always be practically dry, provided it is an inch or more above the adjoining surface, and provided dead grass and leaves are not allowed to wash against the standing grass and form a dam. A crown of * inch per foot of half width is ordinarily sufficient to drain the depressions left in troweling.

Color of Walk.

Ordinarily cement walks have an un pleasant glare, particularly where a considerable area is laid together, as around public buildings, fountains, etc. This glare can be mitigated by coloring the walk. The coloring matter must not contain acids, and must have no effect upon the alkalies of the cement. Dry mineral colors seem to be the only ones that can be used, as apparently all liquid coloring matter destroys the cement. Usually any coloring matter lessens the strength of the mortar, and causes the surface to flake off; and therefore no more should be used than is absolutely necessary, especially of the ochres (§ 948). Ultramarine is an exception to this rule, since a small quantity increases the strength of the mortar, and 30 to 40 per cent may be used without materially decreasing the strength.

Germantown lampblack is more frequently used than any other coloring matter, and gives a bluish gray or stone color of inten sity varying with the amount used. It can be had at drug stores in 1-pound packages, and costs about 12 to 15 cents per pound. Four pounds per cubic yard of sand gives a fairly satisfactory result, although twice as much is frequently recommended. Lampblack is light dry stuff, and it is difficult to get it thoroughly incorporated with the mortar. Some contractors add it to the cement, and mix the two by passing them through a sieve; but a better method is to mix the lampblack with the dry sand by turning once or twice, and then to sprinkle the mass and bank it up, and allow it to stand at least over night, when the coloring matter will be uniformly distributed throughout the mass. The lampblack and sand can

stand any length of time before being mixed with the cement.

Some contractors color only the surface of the walk instead of the entire wearing coat as above. There are two ways of doing this: 1. The coloring matter is added to a mixture of sand and cement of the same proportions as that used for the wearing coat. This mixture is sprinkled over the wearing coat after it is in place and then the surface is floated and troweled. This treat ment is repeated two or three times until the desired shade is obtained. When this method is employed, the wearing coat must •be mixed a little wetter than otherwise, so that the dry colored mortar may be properly worked into the wearing coat. This method of coloring the surface is not so good as the preceding. since the coloring matter is likely ultimately to wear through and leave the walk spotted. 2. Another method of applying the coloring matter is to sift or sprinkle it over the surface, and then to trowel it in. This is a very poor method, since the coloring matter is easily blown away., and the walk is likely to be spotted or to wear so, and also to flake off in places where there is an excess of coloring matter.

Almost any color can be produced by the use of the right coloring matter. The following list of colors and coloring matter is frequently quoted.

Sometimes a very white walk is desired. White can not be produced by adding a coloring matter. Some Portland cements bleach out and make whiter walks than others. To secure a white walk, use white sand or powdered white marble and perfectly clean water, and keep the surface of the walk free from dirt. or dirty water. A very white surface can be obtained by using pure white slaked lime and white sand, but the walk will have no durability. Sprinkling the ordinary cement walk frequently and allowing the sun to shine upon it for a few days after it is completed, seems to bleach it.