Imphal, December 14 2009: For construction and repairing of National Highways up to the stage of laying of bitumen, water bound macadam (WBM) would be replaced by wet mix macadam (WMM) .

Although WMM costs more, roads paved with WMM have greater quality.

Moreover, black-topping can be done soon after laying WMM unlike WBM, said an official source.

Waiting for WBM layer to dry up and solidify often takes days and causes much dusting of the road thereby hampering traffic.

However, a road laid with WMM can be opened to traffic immediately after.

According to procedures of laying WBM, stone types known as IRC (Indian Red Congress) grade I, II and III should be used.

But in Manipur only IRC grade II and IRC grade III are used.

These three grades of stones should be laid out layer above layer before covering it with earth.

Then the layer is soaked with water before running it over by roller to solidify the road surface.

It takes around a month for such a road surface to dry up before black-topping can be done.

In WMM method, stones, binding material and water are mixed proportionately and the mixture is laid out at one time.

Such road once run over by roller can be opened to traffic.

Bitumen can also laid immediately after, said the source.

Some states have already adopted WMM method since a few years back.

As roads laid with WMM have greater quality, the same method will be applied while repairing Moreh-Pallel sector and North AOC-Maram sector of NH 39 on trial basis.

The Ministry of Shipping, Surface Transport and Highways has also instructed the State Government to use WMM in place of WBM.

Subsequently, work orders issued for repairing different segments of NH 39 specified use of WMM.

The Ministry has also categorically informed the State Government that work proposals with WBM components would not be sanctioned.

The Ministry further asked the State Government what WMM machinery it possesses, conveyed the source.

Among local contractors, only one has WMM machinery, added the source.

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