Concrete Roads
and Their Construction

148 CONCRETE ROADS It is convenient when reloading materials on the site to use wagons, carts or boxes which also act as measures. It is of the greatest importance that the transporting, propor- tioning and distribution of the materials should be effected systematically and with a minimum of labour, as it is easy, through carelessness or absence of suitable appliances, to spend a double amount of money on these portions of the work. Keeping Aggregates Clean.—One of the essential but too often neglected features in constructing concrete roads is the delivery of clean aggregate to the mixers. Engineers rightly insist on the use of clean stone, sand and cement ; therefore, wherever possible, the material should not be (lumped on the sub-grade or on the side of the road, since in re-handling it to the mixer it is quite possible that a considerable amount of sub-grade or shoulder material may become mixed with the aggregate. This may largely be avoided by combining the measuring and delivery of the stones, sand, etc., with the transportation of the material direct from the source of supply to the mixer. In most road jobs this can be accomplished by placing the material for a complete batch in specially constructed boxes or carts. These boxes or bodies can be built, or can be obtained from manufac- turers in several sizes; the material is automatically measured to ensure accurate proportions, and so that they can be easily dumped directly into the mixer or into the mixer loading skip. In addition to ensuring the cleanliness of the material, this method of charging the mixer is usually much more economical* than clumping the material on the grade ahead of the mixer, since it eliminates a double handling of all material. A fixed measuring hopper is supplied with Ransome Mixers (supplied by the Ransome Machinery Co., Ltd., London). The hopper is of such dimensions that it contains the requisite quantity of aggregate to form the batch in each size of machine. The door is operated by a hand-lever. Every Ransome Mixer, un- less otherwise specified, is also despatched with a water-measuring tank attached. Various mechanical measuring devices suitable for concrete road materials are on the market, though most contractors will find the divided wagon previously mentioned, or separate “ boxes,” quite satisfactory and free from great liability to error or serious