Concrete Roads
and Their Construction

IN INDUSTRIAL WORKS AND MILITARY CAMPS 75 function in providing for any possible contraction of the concrete by spreading this contraction over innumer- able and practically invisible hair cracks. (d) To provide a simple, cheap and practicable way of readily- assembling the steel, and to ensure that the reinforce- ment, when laid, shall be in its correct position, in the concrete, and also to provide a framework to which any additional bars can be readily attached when required over trenches or other exceptionally weak places. This system of constructing concrete roads was installed in the Royal Victoria Docks in the winter of 1917-18, and has ful- filled all expectations. The proportions of the concrete, the methods of mixing, and construction of the road may shortly be described as follows :__ The lower 7 in. consists of 6 of Thames ballast to 1 of Portland cement, the top or wearing crust of 2 J of f-in. broken shingle, and 1| of sand to 1 of Portland cement. The construction of the road was as follows : After the road bed had been excavated and graded, the reinforcement was laid there- on, the bottom 2 in. of concrete was placed in position, and the reinforcement lifted through it, by hooked bars, so that it rested on the concrete. The remaining 5 in. of the bottom 7-in. coat was then deposited. The top 2-in, coat was afterwards placed in position, tamped and screeded by a specially constructed screed worked by two men, which brought the surface to the actual level and contour required. A special feature in the making of these roads was the machine for fixing, laying and screeding the concrete, which is briefly described in Chapter VI, page 165. Messrs. J. Baker, Sons & Perkins, Willesden Junction.—A con- crete road was laid down at the works of Messrs. Joseph Baker, Sons & Perkins, engineers, Willesden Junction, under the super- intendence of Mr. S. W. Moscrip, the engineer. Having studied the concrete roads of America and of this country, and examined the question in all its bearings, Mr. Mos- crip was satisfied that a concrete road was calculated to meet moie satisfactorily than any other the demands made upon it by the heavy traffic which a road of this description has to carry ; the company therefore decided to give this method of construc- tion a trial.