Bitumen is an essential part of all flexible pavements and is used in large quantities in road construction in our country. When bitumen was being imported. it was coming packed in steel drums. These drums were discarded after they were transported to the site and cut open for taking out the bitumen. As the steel for drums has to be imported. this packing in drums adds considerably to the cost of bitumen and hence to the cost of road construction. It is in this context that the use of bulk bitumen in road construction needs to be encouraged
Apart from the economy achieved by eliminating the use of steel drums, the use of bulk bitumen has the following additional advantages:

(i)  Considerable saving of fuel used in reheating bitumen can be effected
(ii)  Temperature of bitumen can be accurately controlled for various range of       applications.
(iii) Contamination and leakage losses during transport and storage are       avoided
(iv) Better speed of construction and quality control can be achieved
(v)  Saving in foreign exchange is possible because of saving in quantity of        imported steel used for making drums.

For transportation of bitumen from the refinery, hot bitumen at 150 to 170°C is rtlled into tanks mounted on truck chassis or railway flats. These truck mounted tanks with a capacity of around 10 tonnes are well insulated to keep the product hot A dial gauge theremometer provided on the tank indicates the temperature of the bitumen. Drop in temperature of the bitumen while in the tank is 1/2°C - loC per hour depending upon the type of insulation and the ambient temperature. As such normally upto 30 hours from the time of loading, bitumen is hot enough to be pumped out without the necessity of reheating. If the temperature has fallen to such an extent that the bitumen cannot be pumped out, it is heated again by firing oil burners at the outer end of the flue tubes in the tanks. The hot gases traversing through the flue tubes running longitudinally inside the tank transfer heat to the bitumen to bring it to the desired temperature.

At the work site, mobile site storage tank of 3 tonne capacity are required in place of the conventional tar boilers. These mobile tanks are insulated and provided with heating arrangements similar to those of the tank truck and can be towed by means of truck/roller. Hot bitumen from the tank truck is delivered into these mobile site tanks. At work sites where Hot Mix Plants are operating, bigger site tanks of 6 tonne capacity may be provided

The ex-refinery selling price of bulk bitumen is about Rs 700 per M. T. less than that of packed bitumen. It has been estimated that bulk bitumen transported in tankers by road is economical if the destination is within a radius of 400 to 500 km of the refinery. There are a number of refineries in different parts of the country and thus a substantial part of bitumen consumption would fall within the economic ranges of these refineries.
Experience shows that there is some reluctance on the part of some State Public Works Departments to the usage of bulk bitumen. The main reasons for this are the lack of infrastructural storage facilities for bulk bitumen at various sites, consumption being too low or irregular, requirement of advance planning and uncertainties regarding avail- ability of funds. Further there are other problems such as need for reheating of bitumen and transportation of storage tanks in case it is not possible to use the bulk bitumen on the day of arrival Lack of coordination between the field engineer and supplier also discourages the use of bulk bitumen to some extent At present 'about 60 per cent of the bitumen requirement is being supplied in bulk and efforts are on to increase this share to atleast 66 per cent
The time is probably not yet ripe to switch over to bulk bitumen for all types of specifications even for works within the economic range of refineries. However, in situations where large scale works of bitumen-bound specifications are planned, there is definitely a case for use of bulk bitumen for better quality and less cost This would pre-suppose a good coordination and communication between the field engineer and the supply point so that day to day requirements are known well in advance and supply arranged accordingly. It needs a lot of careful planning and efforts to achieve this objective.
It must be emphasised that bitumen is a hazardous material when in a heated condition. All the prescribed safety standards for transportation and storage of such a material should, therefore, be followed as per the requirement of Rules 129 to 137 of the Motor Vehicle Act, 1989.

The Indian Roads Congress is shortly bringing out a Special Publication entitled "Guidelines on Bulk Bitumen Transportation and Storage Equipment". It is hoped that this effort in a modest way would make highway engineers more conversant with the equipment requirements ' for transportation and storage of bulk bitumen for different types of work and induce increased usage of bulk bitumen in the country thereby econo- mising on cost of road surfacing.