White-topping as pothole killer?
Rasheed Kappan and Madhuri Rao, DH News Services, Bengaluru, Oct 15 2017, 3:46 IST
Devastated by record rains, the city’s tattered roads have trapped Bengalureans in a twister of commute woes. In its frantic search for a late remedy, the government has a cure: White-topping, a massive, expensive project covering 29 roads dubbed as a final farewell to potholes. But does the civic agencies’ pathetic record in road works give public confidence?
A massive Rs 972.69 crore in two packages to cover six junctions and the roads. The project is huge by all accounts. Promised are pothole-free roads that last 20-30 years. “Long life, low maintenance cost, low lifecycle cost, improved safety and environmental benefits,” reads the concise project report issued by the Bruhat Bengaluru Mahanagara Palike (BBMP).
The citizens are now at their wit’s end negotiating the 30,000 plus potholes on existing roads. Would they digest it if the Rs 10.40 crore / km white-topping wears off once the spotlights shift elsewhere? Road engineers have already warned that the project will be disastrous if the work quality is poor and not executed with utmost care.
Simply put, white-topping is a cement concrete overlay on an existing bituminous pavement. The claim is that potholes and deformations such as rutting and cracking will be totally eliminated. Besides, the total load-carrying capacity of the existing pavement will increase.
Slopes for drainage
The project might sound great on paper. But unless the road surface is given proper finishing with longitudinal and latitudinal slopes (cambers) to help water drain out to the sides quickly, flooding will recur, warns M N Sreehari, a road engineering expert. “The potholes and all other unevenness should be leveled out. Quality control is extremely important in white-topping,” he reminds.
Great care is a must to maintain the right proportion of cement and concrete. Any dilution could weaken the road surface. “If they use less cement, it will become just like a bituminous road. Lack of adequate curing will shorten the lifespan. Also critical are the gaps between the slabs,” explains Sreehari. Regular maintenance is crucial too once the white-topped road is opened to traffic.
Although white-topped roads fare better in night visibility and lower lifecycle costs, having a proper drainage is a prerequisite, says Ashish Varma, Assistant Professor, Department of Civil Engineering, Indian Institute of Science.
No digging, absolutely
Besides, as both Varma and civic evangelist V Ravichander emphasise, white-topped roads should never be dug up for underground utility work. “Cross-service ducts should be provided to ensure that these roads are not dug. But inter-agency coordination is critical for this. Here, the different civic agencies do not even talk to each other,” points out Varma.
“There is a very important condition when you opt for white-topping a road. You should never touch it. Repairing a dug up white-topped road will lead to a scene far worse than a pothole on a black-topped road,” Ravichander says.
The message is clear: Never try white-topping a road if utility ducts and cross-ducts are not laid. “Increase the footpath width, plan the underground utilities and storm water drain well, and only then think of white-topping.”
A clear example of how not to do white-topping is the Kasturba Road stretch from Hudson Circle to Tiffany's Circle. No provision has been made on the road for utilities. One of the city's widest roads has a footpath that is barely two metres wide.
High traffic volumes
The city has a road network of nearly 14,000 kilometers of which about 1,500 kms covers the major arterial and sub-arterial roads. An estimated 200 km of the radial roads crisscross the Central Business District (CBD), where the traffic volumes are particulary high. Radial roads and the Outer Ring Roads collectively bear the load of about 70% of the average daily traffic.
The huge number of potholes on the existing asphalt roads has injected a sense of urgency into the white-topping project. Repairing the potholes has only been a temporary solution. The continuing rains have severely damaged the black bitumin emulsion used to tar the roads.
How does BBMP justify spending Rs 10.4 crore on every kilometer of white-topping? The Palike officials talk about durability while explaining the process. Says K T Nagaraj, the Palike's Chief Engineer (Roads): “In this project, we mill the roads using milling machines and the existing bituminous pavement is scraped for an equal surface. Once the bitumin is laid, a layer of quality cement concrete of 170 mm thickness will be applied.”
BBMP Commissioner N Manjunath Prasad claims the white topped roads will last 30-40 years. “This is low on maintenance. It also reduces the pollution since the concrete which is laid on the road can withstand the changes in weather,” he explains.
The project covering 29 roads was launched early October. Work has already started on Hennur Main Road and is expected to be completed in 11 months. The project has been divided into two packages and the contracts granted to two firms, the Nagarjuna Construction Company and Madhukon Project Limited.