North Bengal variety of stones unfit for bituminous layers of roads: Report

North Bengal variety of stones is unfit for constructing bituminous layers of roads and heavy concrete structures, said experts.

A committee to test the strength of North Bengal variety of stones was set up a year ago following instructions from Chief Minister Mamata Banerjee during her visit to the area.

The committee, entrusted to combine a report on the usability of these stones, will submit a report to the state government soon. The five-member committee comprises senior officers of the state Public Works Department including the engineer-in-chief and experts from IIT Kharagpur, Jalpaiguri Engineering College and Rites. They are two senior officials of the PWD in the committee as invitee members as well.

It was in mid-2016 when the Chief Minister went to North Bengal and found that this variety of stones was dumped at a particular place. The whitish-coloured stones attracted the attention of the Chief Minister as they looked very different unlike those from Pakur, that are usually black or dark grey in colour and irregular in shape. Basically, this variety of stone is obtained from the river beds at certain places in North Bengal.

After inquiring, the Chief Minister came to know that the stones were brought for construction of roads. In a bid to know whether such stones are fit for construction of roads and heavy concrete structures, the state government had set up the committee.

Tests on this variety of stones have been carried out in laboratories by experts and they have also gone through several related reports of Rites. At the same time, different varieties of stones were being compared with those of the North Bengal variety. The experts had carried out the study on different types of North Bengal variety of stones.

Following the necessary tests, members of the committee held a meeting at the state Secretariat, Nabanna, a few days ago in which they came to a final conclusion regarding the matter.

Sources said the experts have come to a conclusion that the North Bengal variety of stones is unfit to construct the bituminous layer of roads. But it can be used for laying the "under layers" and that too only after properly judging its quality which will be done based on the place from where it has been excavated and other relevant aspects.

Similarly, it has been found unfit to construct heavy concrete structures as well. However, it can be used in construction of minor "low-strength" structures.