Concrete Roads
and Their Construction

IN INDUSTRIAL WORKS AND MILITARY CAMPS 81 fortunately possible to divert the traffic, the whole of the road was scarified to a depth sufficient to form a new bed, all surplus material being screened and the recovered metal carted away for use on the second half of the road. A good solid foundation was ensured by filling in, watering and ramming any soft places in the bed; the latter being finally finished off to the required camber. On the bed was laid the reinforcement—a metal mesh—a lap of 4 in. being arranged at the junction of each width, and a lap of 12 in. where one length ended and another began. The aggregate employed was shingle dredged from Langston Harbour, in the vicinity of the Works. This was mixed with Portland cement in the proportion of 6 : 1 for the lower course of 4 in., and 3 : 1 for the wearing coat, the shingle for the latter all passing a | in. screen. On depositing the concrete the reinforcing fabric was lifted and well shaken, and the concrete rammed to a depth of 2 in. below the reinforcement, the position of which was thus uniformly 2 in. from the under surface of the slab. Great care was taken that the upper 2 in. of fine concrete should be laid before the lower layer had set, and the work was finished off each evening at a straight edge placed transversely across the road. At the end of each day’s work a strip of reinforcing fabric some 3 ft. wide was so laid across the road as to bond the two days’ work together, half the width being left projecting. The formation of the correct camber was effected by the use of two parallel screeds, placed one on each side of the road, and a template faced with hoop-iron, which was dragged backwards and forwards along the screeds after the laying of the concrete in each section. This gave a very good surface. Good progress was made by the above method, the average rate of completion being about 30 ft. run per working day. As the concrete was laid and the surface finished the work was protected from the sun by means of corrugated iron supported on poles. This temporary roof was moved daily to follow the work, and was replaced by a layer of wet sand, which was kept well wetted for three to four weeks after laying. Fig. 53 shows the sub-grade in the foreground, the roll of reinforcing fabric, the template and the corrugated iron protection. When the concrete had thoroughly matured, the sand was removed, and finally a coat of hot dehydrated tar applied, the whole being dusted over with coarse sand. G