Concrete Roads
and Their Construction

SUGGESTIONS FOR FORM OF SPECIFICATION 181 Placing the Concrete 13. Weather Conditions.—So far as is practical, all work should be done during the summer months, but in the event of concrete roads having to be laid when the thermometer is below 39° F., care shall be taken that the sand and stone shall be heated before being introduced into the mixing drum, or that an intense heat shall be brought to bear on the concrete during the mixing process. During such weather conditions, after material is put in place on the road, care should be taken that it is thoroughly protected, preferably by tenting with canvas under which steam pipes or braziers shall be introduced to ensure that the temperature of the concrete will remain above freezing point until the concrete has had time thoroughly to set. The concrete shall be deposited over the whole width of the road at one and the same time, except in cases where it is impossible to divert the traffic for the time being. The sides of the road, where there is no kerb, and the encl of each, day s work, shall be supported by a wooden or metal form sufficiently strong and properly supported to resist straining out of shape under the pressure of the concrete. All mortar and dirt shall be removed from forms which have been previously used, and the forms shall be greased or oiled before any concrete is deposited against them. The side forms shall remain in place until the concrete is set sufficiently hard to permit of the removal of the forms without damage to the edges. In removing the form at the end of the previous day’s work, in order to resume operations the next day, very special care will have to be taken to see that the concrete is not damaged, and, furthermore, in beginning the deposition of concrete special care must be taken with the tamping of the concrete to see that the previous day’s work is not disturbed or damaged in any way. This will, inevitably, be one of the most critical points in the road and will merit the very closest attention and supervision. If desired, joints filled with material complying with paragi’aph 6 may be provided between each days work, but shall not exceed ] in. in thickness. The value of these joints, however, is not proved, and they undoubtedly introduce weak points into the road. Longitudinal joints similarly filled may also be provided alongside the kerb or channelling (if any) if desired. 14. Thickness.-—The total thickness of concrete for both one and two-course roads shall be specified, and it will be found that, under average conditions, a total thickness of about 6 in. will probably be sufficient. The surface course of two-course roads shall be approximately 2 in. thick.