Friday, 17 August 2018

Material Required For Construction of Water Bound Macadam (W.B.M) Road

What is Water Bound Macadam(W.B.M)Road

The pavement made of crushed or broken aggregates, mechanically interlocked by Rolling and filling the voids with screening and binding material with the assistance of water, is called water bound macadam(W.B.M)Road. 

The W.B.M can be used as a sub-base ,base course or surface course .The thickness of each compacted layer of W.B.M ranges from 10 cm to 7.5 cm depending on the size and gradation of aggregates used.

Material Required For Construction of Water Bound Macadam (W.B.M) Road

The materials required for construction of W.B.M road are coarse aggregates,screening and binding materials where necessary.

a)Coarse Aggregates

The coarse aggregates used in W.B.M generally consists of hard varieties of crushed aggregates or broken stones. However ,soft aggregates like over burnt bricks metal ,kankar and laterite may be used.


The screening are used to fill up the voids in the compacted layer or coarse aggregates.The screening consist of aggregates of smaller size ,generally of the same materials as the coarse aggregates .From the economic considerations,kankar,moorum or gravel can be utilized as screening materials.

c)Binding Materials

Binding materials consist of fine grained materials. kankar nodules or lime stone dust etc are used as binding materials in W.B.M construction.