Picking up Road Surface & Re-sectioning

        The first operation in resurfacing a macadam road is picking up the old road surface. This is a hard operation and is usually scamped. It will be worthwhile to use pavement breakers with a compressor unit for this purpose.

        After picking up the next operation is to section the road to proper camber. This, is, to be done with the old picked up metal. But if the picked-up metal is not sufficient for the purpose some new material may bead led to it. For sectioning proper wooden templets should be used.

A fact which is probably not known, and which is not therefore done is that after sectioning with the old metal with some new metal added, if necessary, the road is to be rolled to proper section. The final section of the road is to be brought out in this rolling before adding the new metal. 

Camber

        An old Public Works Department Circular specifies a camber of 1 in 36 for Macadam roads. It is observed that the road crown flattens out slowly under traffic and the original camber of 1 in 36 practically becomes flat and in many places the road surface becomes saucer shaped.

        It is recommended that the initial camber for macadam roads should be 1 in 24 or even 1 in 20 so that even after flattening of the crown an appreciable camber of 1 in 30 or so will be obtained. Hardly few complaints received till date about excessive camber and that also on rare occasions, that also because of side widths were allowed to wear down too much below the metal surface which then looked a dangerous hump. In the matter of camber, it is much better to do on the excessive side than otherwise. The wooden templates should therefore be prepared to camber of 1 in 20.

Consolidation

        Apart from the quality of metal this is the one single item which makes for success or failure of a macadam road and too much care can never be lavished on this item.

        The success of a macadam road depends on the extent to which interlocking of the metal stones is secured. This is done by rolling and the results depend on the weight of the roller and the number of passes done with it.

        There is an excellent paper by Mr. Mckelvie and Raghavachari read before the Indian Road congress in the year 1946, which leaves practically nothing to be said about macadam roads. This paper must be read and re- read and digested by everybody who has to do anything with this type of road and not only read but must be put in actual practice.

        For pick and roll activities the minimum weight of roller must be 12 Tonnes and may preferably be 15 Tonnes if the metal is sufficiently hard.

        Sheep foot rollers are useful in consolidating banks formed of clay material, such as many or soft or Sherya' murum.. Too much clayey material like black soil is of course not to be used at all in the bank work.

        Not only the weight of the roller but the number of passes of the roller over a given spot in equally important. Paper by Mr. Mckelvie and Raghavachari recommends Minimum 90 passes of the roller over any spot are generally required for getting satisfactory consolidation.

        Metal must be rolled dry with a heavy roller to refusal i.e. till no movement in the metal is soon under the roller. Another test is with the fully filled water cart. such a cart passing over must not leave impression on the surface nor must cause any movement in the metal.

        Till dry consolidation is done to this stage, not a drop of water must be put on the road. It is observed in many places water being sprinkled on metal as soon as roller begins to work. The idea of these people seems to be that macadam surface in something like concrete which has to be mixed with sufficient quantities of water or with liberal use of it. And when they are in a hurry to put murum on such an insufficiently consolidated and liberally drenched metal layer it literally turns into a surface of mud concrete. How long can you expect such surface to last under the heady and fast-moving present-day pneumatic Tyre traffic. It is no wonder that such a road surface is very soon ripped up by such traffic.