Concrete Roads
and Their Construction

CHAPTER 111 CONCRETE ROADS IN INDUSTRIAL WORKS AND MILITARY CAMPS The Port of London Authority.—The system of reinforced concrete roads introduced and developed by the Port of London Authority presents many features of interest. The road slabs are 9 in. to 10 in. thick, including a top wearing crust of 2 in. The method of reinforcement, designed and patented by Mr. J. H. Walker, Assoc.M.Inst.C.E., of the Port Authority, was the outcome of the difficulty foreseen in laying a satisfactory concrete road upon the particularly soft ground of which the land in the vicinity of the docks is composed. The reinforcement provides for top and bottom layers of reinforcing bars combined and inter- locked with zigzag diagonal tension members in such a manner as to form a rigid mattress to which any additional bars may be attached as required (see illustration). The steel is delivered direct to the site from the rolling mills in coils of in. diameter wire and straight lengths of | in. or in. bars. The men quickly and economically bend and assemble the bars on rough benches, which latter are moved forward as the road progresses. Very careful consideration was given to the question of rein- forcement. The reasons for adopting such a type of double reinforcement, with its accompanying great advantage of pro- viding steel diagonal members to counteract the shear or diagonal tension stresses, were as follows :— (a) Economy. (6) To provide two layers of reinforcement to meet the flexure and contra-flexure stresses in the slab imposed by the heavy rolling traffic. (c) To eliminate the necessity for providing objectionable expansion joints and to prevent the concrete from devel- 69