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this material with the grader and roll it thoroughly. Follow the rolling immediately with an application of f U.S. gallon per square yard of bitumen, cover as before with gravel, and roll, and the road is ready for traffic." Such a road is said to be able to carry up to eight hundred vehicles per day. Bituminous Macadam. A bituminous macadam pavement is one having a wearing-course of macadam with the interstices filled by penetration methods with a bituminous binder. It is not durable heavy traffic, but stands up well under moderate loads. Advocates of bituminous concrete, and salesmen, are often hoard disparaging this form of pavement, but nevertheless it holds a definite place in modern road-construction, chiefly on account of its low initial cost and the small amount of equipment required to lay it. It must be remembered that unctions of the bituminous material in bituminous macadam and bituminous or asphaltic concrete are not quite analogous, although the adhesive quality of the material is the essential quality in both cases. In the case of asphaltic concrete the bitumen filler and aggregate go to make a dense mixture, which when rolled in place forms a structure capable of taking loads, but in the absence of tho bitumen the mixture would not take loads without lateral displacement of the material. In the case of bituminous macadam, before the application of bitumen tho structure is capable of taking loads without lateral displacement, on account of the interlocking action of the mineral aggregate. Under this method a dense pavement is not possible, neither is it looked for, as the function of the bitumen and chips is to provide a matrix which will waterproof the surface of the pavement, and will not be sucked out by rubber-tired traffic in the way the binding constituents of an ordinary macadam road are sucked out. A bitumen of higher penetration is required for a bituminous-macadam road than for a bituminous-concrete road. The consistency must be such that when in a melted condition it is fluid enough under proper working-conditions to flow freely and coat the coarse stone aggregate with a thin film. When cooled to summer temperatures it must be stiff enough not to flow ; when still further cooled to winter conditions it must remain plastic enough to contract without cracking. This question will be dealt with more fully under the heading of " Bituminous Materials." The stone used should be sufficiently hard and tough to withstand thorough rolling without crushing, as if crushing takes place proper penetration of the bitumen cannot be attained. Should a comparatively soft stone be the only kind available, a larger-sized coarse aggregate should be used to mitigate somewhat the effect of the further crushing under the rolling. With stone of good quality the size used should be from 1 in. to If in. The stone is spread on a water-bound-macadam foundation to such a depth that when compacted the layer will bo from 2 in. to 3 in. thick. The course is then rolled. As the chief reliance is placed upon tho interlocking action of the stone to obtain stability, rolling must be done until full compression has been obtained and all lateral movement has ceased before the bituminous binder is applied. The importance of adequate rolling cannot be emphasized too much, as a large number of failures—or, at least, very undesirable features ■ —in the finished pavement can only be assigned to insufficient rolling before applying the binder. Unless the coarse stone is rigidly keyed together to prevent lateral displacement the following application of bituminous material _ will have the effect of surrounding tho stone with a lubricant which under summer conditions and under traffic favours the readjustment and constant displacement of the stone aggregate. This will produce ruts and other depressions, and corresponding ridges, over large parts of which will not only make travel unpleasant but will also be destructive to vehicles. The condition of such a pavement becomes worse and worse in time as vehicular impact increases and the depressions increase in depth and the ridges in height. Compacting of the bottom course being completed, hot bituminous material at tho rate of about If imperial gallons per square yard is then uniformly applied under pressure, in such quantity so as not merely to cover the surface but also to flow into the voids between the stone fragments. The surface voids in the course are next filled by spreading and rolling in a thin layer of chips. No bituminous material should be applied unless tho entire depth of coarse stone is thoroughly dry and the air temperature in the shade is over 50° F. After sweeping off all unabsorbed chips a further application of bituminous material is made in an amount just sufficient to provide a thin coating of tar or asphalt, which is immediately covered with stone chips and rolled. This second application is usually at the rate of about f gallon to the square yard. It is of the utmost importance that all stone, coarse and fine, should be reasonably clean and free from dust in order that it may be thoroughly coated with the bituminous binder. If necessary the stone should be flushed with water, but it must be thoroughly dry before the application of bitumen. If too much bitumen is used in an independent mat will form, which will develop corrugations. In adopting American specifications, the difference between the United States gallon and the imperial gallon should always be borne in mind. It may mean the difference between success and failure. Bituminous or Asphaltic Concrete. There are a number of forms of bituminous paving which can be classified under the above heading. The essential difference between the various forms is chiefly in the grading and quantity of tho coarser aggregate. Asphaltic concrete is really a sheet asphalt mixture with the addition of a percentage of aggregate varying from 1 in. to J in.