Concrete Roads
and Their Construction

IN THE UNITED KINGDOM—METROPOLITAN 5 and this was excavated to a depth of 9 in. The foundation, which was found to be fairly solid, received no special prepara- tion, and after being rolled was ready to receive the concrete. The two-course method was adopted, the lower being 4 in. thick and the wearing coat 2 in., the latter being laid before the former had set, so that the whole might form one monolithic structure. The concrete for the lower consisted of a 6 : 1 mixture, and the material from the old macadam road was used as the aggre- gate. The upper course was composed of a 3 : 1 mixture, the aggregate in this case also being the material from the original road, crushed, washed and graded from | in. down. By the use of the material from the old roadway a very consider- able economy is effected by the elimination of costs for the purchase and transport of new aggregate. With a view to further economy, the Council, in 1919, purchased a washing and grading machine which has already more than paid for itself. (See Chapter VI.) The reinforcement was placed 2 in. from the bottom, i.e., in the middle of the bottom course. It consists of j in. rods simply interlaced, like bedstead laths, and wired at the ends, succes- sive lengths being joined to each other by being hooked together. The method of laying alternate sections was not adopted, but each day’s work was finished off by a clear vertical edge as shown in Fig. 1, against which the next day’s work was butted without the intervention of a joint filler of any description. The reinforcement does not extend over these joints, so that each section consists of a slab of reinforced concrete in itself. The contour was formed by the use of pins, which were removed as the work proceeded. For finishing the surface, a special tool has been devised, which consists of a metal plate 15 in. square, to which is attached a handle fixed obliquely so that the tool can be operated from the side of the road. The surface was rubbed over with this tool, and parts of the road which were found to be too smooth were roughened with a bass broom. The joints were tarred first, and after an interval of some weeks the whole road was coated with tar and sand. This gives a sur- face which is not too smooth and which affords a good grip for horses and wheels. The traffic was kept off the road for about three weeks. The roads in question are of varying character. Whilst not