According to Girish Jaysing Arekar, council member of the Indian Road Congress, the use of substandard construction material, lack of road maintenance and heavy traffic are some of the factors responsible for the formation of potholes
An internal road at Everard Nagar, Sion East, yesterday. Pic/Kirti Surve Parade
Following a few spells of rain, potholes, the bane of all commuters, have once again started appearing on the city’s tar and asphalt roads. To understand why this phenomenon is unfailingly witnessed every monsoon season, mid-day turned to experts, who said craters primarily form due to water infiltration through cracks or poor drainage.
An Eastern Express Highway stretch near Priyadarshini junction in Sion East yesterday
Professor Manoranjan Parida, director, Central Road Research Institute (CSIR), said potholes primarily form due to water infiltration through cracks or poor drainage, which weakens the pavement structure. “Factors such as traffic loading, ageing of bitumen, poor construction practices, and pre-existing cracks further accelerate the deterioration. Improper implementation of the job mix formula [detailed recipe for creating a specific construction mixture] — such as insufficient binder content and poor-quality aggregates — also contributes to pothole formation,” he said.
An internal road near MMRDA Grounds, BKC
“Potholes are more common during the monsoon due to excessive moisture, which weakens pavement layers and accelerates deterioration. Continuous water flow washes out fine particles through cracks, while blocked drainage leads to water accumulation,” Prof Parida added. According to the CSIR director, key contributing factors to the creation of craters include inadequate pavement thickness, delayed maintenance, subgrade soil instability, and construction during wet conditions. “Timely crack sealing, proper drainage, use of high-quality materials (bitumen and aggregates), improved mix design, ensuring proper compaction and adequate layer bonding, and regular maintenance help in reducing pothole formation,” he said.
An internal road at Everard Nagar, Sion East. Pics/Kirti Surve Parade
According to Girish Jaysing Arekar, council member of the Indian Road Congress, the use of substandard construction material, lack of road maintenance and heavy traffic are some of the factors responsible for the formation of potholes. “Due to variation in temperature during the summer and monsoon season, road surfaces expand and contract, resulting in the formation of small cracks. When rainwater enters these cracks, they develop into potholes,” he said.
Water damage
Jagdeep Desai, architect, academician, founder-trustee and chairman of the Forum for Improving Quality of Life in Mumbai, said, “Asphalt roads require a well-compacted, appropriate base [foundation] to level the next layers. There must be a non-permeable film or sheet to minimise groundwater from seeping up, a specified sub-base and then the top surface, each with the required thickness and materials.”
Jagdeep Desai, chairman, Forum for Improving Quality of Life in Mumbai
He added, “Ideally, the base should be comprised of well-compacted rubble, then tar felt or asbestos cloth or chemical application, and a sub-base of cement concrete, with the asphalt, mastic on top. The entire process must be carried out in totally dry conditions to allow the hot surface to cool at the right temperature to gain the designed binding, bonding and finally hardness. Any crack will allow water to get in, and due to the constant vehicular movement, the materials get separated, forming potholes.”
Manoranjan Parida, director, Central Road Research Institute
“If there is no damp-proof layer, groundwater will cause the road to sink, creating a break in the surface. Once potholes are formed, repairing and resurfacing require exactly the same process. If the proper process is not followed or the right materials are not used, chances of potholes former during showers are high. The pothole has to be absolutely dry and free of any other particles.
The asphalt poured into it must be allowed to cool in dry conditions to ensure it is hardened,” said Desai. Desai also pointed out that as most of such work is done by unsupervised daily wage labourers, who work for the contractor with the lowest tender, and probably without following specifications. “Unless entire roads are redone in the specified manner, such defects will continue,” he added. Mumbai also faces the issue of waterlogging owing to the clogging of the drainage system with garbage and silt. Because of this, water accumulates on roads, resulting in potholes.
Weakening of bond
Biju Augustin, an independent civil engineer, said, “Bitumen, found in tar, asphalt and mastic, is a sticky substance made from the last remains of petroleum, which comes from deep under the sea. When asphalt stays wet for too long, the bond weakens, and the surface starts to break. Poor road slope, bad drainage, water sitting on the surface, weak base layers, and improper sealing allow water to seep in and damage the foundation. During the monsoon, water makes things worse by turning the base soft and unstable. Even when potholes are patched, the real issue, the untreated base, remains, so the problem keeps coming back.”
What is a pothole?
As per the experts, potholes can be defined as bowl-shaped cavities that form in the upper surface of a tar/asphalt/ bitumen road. Are classified in three categories: Small (25 mm deep and 200 mm wide), medium (25 mm to 50 mm deep and 500 mm wide) and large (more than 50 mm deep and 500 mm wide).
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