Amidst ferocious heat wave in the country, road surfaces have melted in several districts as most highways were constructed with traditional bitumen, which cannot withstand the extreme heat, according to experts.
They also suggest using polymer modified bitumen (PMB) to protect the highways in the ongoing extreme weather.
The PMB represents a group of road bituminous binders specifically designed and manufactured to improve the durability of asphalts and increase road traffic safety through the addition of specific polymers to the mix.
The mercury is now hovering above 40 degrees Celsius in most districts of Dhaka, Khulna and Rajshahi divisions with this season’s highest 42.7 degrees Celsius recorded in Chuadanga district twice.
However, experts said the melting of road surfaces outside Dhaka in the temperature from 37 degrees Celsius to 42.7 degrees Celsius is not normal, suspecting that tar might have been used in those roads instead of asphalt.
They suggested using PMB for road construction amid global warming. This type of bitumen is also used in the US and neighbouring India for longer durability of roads.
Noting that the quality of PMB goes down if it is kept stored for many days, the experts underscored the need for using PMB produced in the country instead of going for imports.
Prof M Hadiuzzaman, an infrastructure expert and a teacher at the Bangladesh University of Engineering and Technology, said the standard of polymer modified bitumen is fine and its heat-tolerant capacity is also high.
He, however, said the bitumen costs much if imported.
Generally, 60-70 grade bitumen, whose melting point is 48°C-52°C, is used for road construction. The melting point of asphalt produced by state-run Eastern Refinery is 52°C-58°C.
However, the melting point of PMB is over 70 degrees Celsius.
The existing rules allow vehicles having a maximum capacity of 18 tonnes to ply country’s roads. However, vehicles carrying as high as 40 tonnes are plying those violating the rules.
Meanwhile, polymer modified bitumen is being used for carpeting the Dhaka-Rangpur highway as part of the second phase of the South Asia Subregional Economic Cooperation (SASEC) project.
The experts said if the roads are constructed with PMB, vehicles with 50 tonnes to 70 tonnes will be able to run on those.
Bangladesh needs to ensure a sustainable communications system for becoming a developed country by 2041, the experts said, underling the need for using PMB for constructing roads and highways used by heavy vehicles.
BDST: 2015 HRS, April 29, 2024
MSK/SMS
