There are different stages of road development. But among all of them, Macadam road is the most successful type of road. Some detail features about macadam road are:
-John Macadam 1756 -1836 AD was the surveyor of general of a road in England who put forward an entirely new method of road construction.
-The macadam method is the first method based on scientific thinking.
-It realized that the stresses due to wheel load get decrease at the lower layers & so it is not necessary to provide large layer pavement.
-The importance of subgrade drainage and compaction was recognized so the subgrade was compacted and was prepared with across slope (1 in 36 ).
There are four types of Macadam roads and they are:
a. Water Bound Macadam
In this type, broken stones are bounded with the help of stone dust and water during the construction process.
b.Traffic Bound Macadam
Broken stones or gravels are generally used as a wearing. Multi-layers of stones and gravels are provided in this type.
Bitumen is used as a binding material to bind stone chips and also to bind base and sub-base courses.
d. Cement Macadam
Cement macadam is quite similar to bitumen macadam. Cement is used as a binding material instead of bitumen.