TYPES OF MACADAM ROAD
Macadam roads can be classified into following types:
1) Water bound macadam
2) Traffic bound macadam
3) Bituminous macadam
4) Cement macadam
1) WATER BOUND MACADAM : It is the layer of broken stone aggregates bound together by stone dust or screening and water applied during construction, and compacted by heavy smoothed wheel rollers.
2) TRAFFIC BOUND MACADAM : It is the wearing course composed of broken stones or gravel, consolidated by the action of traffic. This type of surface is generally built gradually by successive application of two or more layers.
The compacted thickness of each layer may vary from 2.5 to 5.0 cm.
3) BITUMINOUS MACADAM : It is the compacted layer of clean crushed stone of reasonably uniform in size. Over this layer, a second layer of crushed stone together with bituminous material heavily sprayed. Much of the bituminous material penetrates into the voids and binds the stones together. To fill the surface voids of the first course, a uniform thin layer of smaller aggregate is spread and rolled. Then, again a light application of bituminous material is applied and a thin layer of still smaller aggregates is spread and rolled. This type of road is generally known as penetration macadam.
4) CEMENT MACADAM : It is similar to bituminous macadam. The only difference is that in this case, cement is used in place of bitumen.
