"All this has reference mainly to roads that have never been oiled before. When it comes to oiling a road the second, third, and later seasons, the operation is somewhat different. Should the oiled surface be cut through and chuck holes formed (but there will be very few holes if the road has been properly looked after), we go over these in the manner previously noted for repairing chuck holes, and then apply a dressing of oil to the whole surface, just enough to saturate the loose material and secure a very slight penetration into the old oiled surface. Here I will call attention to a danger we may fall into, that of putting too much oil on the smooth, hard oiled surface we have previously obtained, softening it, and putting it in condition to rut, especially under heavy loads. We may in this way lose a part of the results of the • previous year's work. I made this mistake on a road last summer, so can speak from experience. But enough oil should be put on to cover the entire surface as with a thin sheet. Then there will be a surplus of oil, and the road, if left without further attention, would be sticky and very unpleasant to travel over for a considerable time after the application. We therefore follow this application on smooth hard roads that have previously been oiled, with a sprinkling of sand, using fine gravel and sharp sand, such as builders use in their mortars. This takes up the surplus oil and adds to the wearing surface, and renders the road at once comfortable to travel over. The sand soon becomes incorporated with the rest of the road material and packs down smooth and hard. The quantity of sand put on is just sufficient to take up the surplus oil and no more.
"We frequently use this sanding process also when applying oil for the first time to a hard smooth road. We have used it on a macadamized road in which the surface was too tight to absorb the oil, and obtained excellent results. It is useful also where oil is applied to a tight adobe or other clay road. With the oil and sand a wearing surface may be built up on the clay and be made to last, while without the sand the oil has a tendency to ball up with the clay dust and carry off. "
Oil applied to a road surface in this manner is ab sorbed by the material of the road covering to a small depth, varying, according to the character of the material, from about one half inch to if inches. This forms a thin coating of oiled material over the surface of the road, which prevents the formation of dust and assists in preventing water from penetrating into the road when rain comes upon it.
In order to secure a greater penetration of oil, in some localities, the soil of the road is loosened by the use of a harrow to a depth of about two inches, before the application of the oil, and is then mixed thoroughly by harrowing again before being compacted by the roller. The method of application varies with the character of the soil, hard soil needing to be loosened and harrowed, or to have a coating of sand added, while sandy soils may be oiled without being disturbed.
In oiling a road for the first time, two applications of oil are usually made, the second application being made at from one week to three months after the first one. In most instances the second application of oil is accompanied by a thin coating of sand or fine gravel, which takes up the surplus oil and forms the wearing surface of the road.
Oil. The oil used for road improvement is commonly crude asphaltic petroleum, with specific gravity to 14 degrees, Baume, and containing from 30 to 6o per cent of "D" grade asphalt. In the earlier work the oil was always applied hot, at temperatures from 150 to 250 degrees Fahr. In later practice cold oil has frequently been used and each method has its advocates.
The amount of oil required varies with the charac ter of the soil and the method of treatment. As much should be used as the soil will take up. The proper amount can only be judged by experience with the soil to be treated. The quantity of oil used varies from about one-half gallon to gallons per square yard of road surface for the first application, and one-half to i gallon for the second application. The maintenance of the roads usually requires an applica tion of oil each spring, the quantity required decreas ing from year to year.