Concrete Roads
and Their Construction

USE OF CONCRETE FOR ROAD ACCESSORIES 191 The advantages of concrete ovei’ iron for pipes are the low initial cost, and the fact that concrete does not corrode. Modern scien- tific research suggests that the corrosion of iron pipes is largely due to electrolysis ; in a properly made concrete pipe in which the reinforcement is completely embedded this clanger is eliminated, with the result that the life of such pipes is indefinite. In order to avoid disturbance of the concrete roadway, in all cases where it is possible to do so, sewer pipes, gas and water mains and electric conduits should be laid under the pavement where they would be more accessible, and a minimum of inter- ference with the traffic would be caused when repairs were necessary. Manholesand Inspection Chambers.—Fig. 128 shows a concrete man- hole. This, of course, could be moulded in situ, but a more con- venient form of construction is that adopted in the case of the manhole shown in the illustration ; that is to say, a series of pre-cast concrete rings which, when the excavation has been macle, are lowered into position, one on top of the other until the surface is reached, the joints being grouted if necessary according to circum- stances. It will be seen at once what a saving of time is effected by this method over the old practice of bricking up the manhole. Inspection chambers may be constructed in the same way with pre-cast concrete blocks. Fence Posts and Gate Posts.—The value and importance of good fencing are appreciated by all who are responsible for the enclosure of land and who know from experience what constant attention, time and expense are required in order that the fences may be kept in proper condition. The material most commonly used for fencing is wood, but this is not only high in price and increasingly difficult to obtain, but, used for this purpose, it has a short life, is expensive to maintain, and is not fireproof. For these reasons, wood is being rapidly and extensively replaced by concrete since this material meets all the demands made upon it. The reinforced concrete post is reason- able in first cost, it may be made on the spot if so desired, local unskilled labour can be used in its construction, it may be moulded to any design, is hard and strong, does not decay, requires no painting, is fire-resisting, and with ordinary usage is practically everlasting ; indeed, after a period of years when a wooden post would have to be renewed, the concrete post is stronger than when it was first put into the ground. The utility and the economy of concrete for this purpose are demonstrated by the fact that this form of fencing is being adopted to an increasing degree by municipal bodies ; and those who travel