Wet Mix Macadam:
For heavily trafficked highways, the granular bases are constructed using Wet Mix Macadam (WMM). The WMM is a specification in which well graded aggregate is mixed with water in a mixer and the mix is laid by a paver and rolled by a roller. Two gradings are used, one with graded aggregates below 53 mm (40 mm nominal size) and the other with aggregates below 26.50 mm (25 mm nominal size). The advantages of WMM over WBM are:
(a) The stone aggregates are well graded and hence a greater interlock results.
(b) Since it is laid by a paver, the resultant surface is even.
(c) Since excess water is avoided, the sub-grade does not get saturated with water and lose its strength.