Concrete Roads
and Their Construction

MECHANICAL DEVICES FOK MAKING ROADS 159 mechanically distributing the concrete after the mixing is com- pleted. This is accomplished by means of a pivoted chute into which the material is dumped from the mixing drum. A wider range of distribution can be effected by means of a boom and bucket arrangement. These booms are macte in varying lengths to 25 ft. A bucket attached to an endless rope is drawn in towards the mouth of the mixing drum and receives its charge; the wind- ing gear is then reversed and the bucket drawn out along the boom to the point of discharge, where an automatic trip arrange- ment causes the bottom doors of the bucket to drop open. As the boom is pivoted so that it will swing through 180 degrees, a very large area can be covered. Since road work requires that the mixer should be moved frequently as the work progresses, it has been found advisable on most paving mixers to arrange for power traction derived from the engine which operates the mixing drum. Certain types of mixers are also arranged so that from the same source power is derived for steering the machine during the moves. Mixers of the above type can be supplied by the Ransome Machinery Co. Ltd. (Figs. 102 and 103), by Messrs. Stothert & Pitt, Ltd. (Figs. 104 and 108), Messrs. Gaston, Ltd. (Figs. 105 and 109), and by the Allied Machinery Co., Ltd. (Figs. 113 and 114). The “Winget” Mixer, which has a capacity of 3 cubic feet, lias been fitted with special mixing arms (in place of the chain spades illustrated in Figs. 106 and 107) for wet concrete, and is as suitable for road work as for site concrete and trench concreting. Laying the Concrete The mechanical devices employed in laying the concrete on the roadway include : (i) The forms or shuttering boards which pre- vent the material from flowing outside the prescribed limits and also determine the thickness of the layer of concrete ; (ii) distribu- ting devices used for applying the concrete to the road surface; (iii) the devices used for spreading the concrete. The forms or shuttering boards are held in position by clamps of any convenient pattern. As wooden forms easily warp, they can only be used a limited number of times and are more costly than appears at first sight, it is usually more economical in every way to use steel forms, such as the Blaw forms, made in America, but which may be obtained in this country. These are shown in Figs, 110 and 11^.