As the United Kingdom experiences record-breaking temperatures above 40 degrees Celsius, a peculiar phenomenon has captured public attention: roads are melting across the country. This has sparked curiosity about why British roads soften and deform under heat that is common during Indian summers, where roads remain largely intact despite temperatures often exceeding 50 degrees Celsius.
Asphalt Composition Differs Between UK and India
The primary reason lies in the type of asphalt used. In the UK, roads are typically surfaced with a bitumen-based asphalt that has a softening point around 45-50 degrees Celsius. This formulation is designed for the country's normally mild climate, where temperatures rarely exceed 30 degrees Celsius. When the mercury hits 40 degrees Celsius, the asphalt softens, becoming pliable under the weight of traffic, leading to ruts, cracks, and surface deformation.
In contrast, Indian roads use a harder grade of bitumen with a higher softening point, often above 55 degrees Celsius. According to the Indian Road Congress, specifications require bitumen to withstand extreme heat. Additionally, Indian road construction incorporates larger aggregates and stone chips that provide structural integrity even when the binder softens.
Construction Techniques and Climate Adaptation
Indian road builders also employ different techniques. They use a thicker base layer and often include a mix of concrete in high-traffic areas. The use of stone mastic asphalt, which is more resistant to deformation, is common. Moreover, roads in India are designed with drainage systems to prevent water damage, which can exacerbate heat-related softening.
Dr. Rajesh Kumar, a civil engineer at the Indian Institute of Technology, explained: "Indian roads are built to withstand extreme temperature variations. The binder used is of higher viscosity, and the aggregate interlock provides additional stability. In the UK, the focus is on preventing cracking due to cold and freeze-thaw cycles, not heat."
Climate and Maintenance Differences
The UK's sudden heatwave is an anomaly; the country's infrastructure is not designed for such extremes. The Met Office reported that temperatures in July 2022 exceeded 40 degrees Celsius for the first time. In response, many roads were temporarily closed or speed restrictions were imposed to prevent damage.
India, on the other hand, experiences sustained high temperatures for months. The Ministry of Road Transport and Highways mandates that all national highways use bitumen with a softening point of at least 55 degrees Celsius, and in some regions, polymer-modified bitumen is used to further enhance resistance.
Global Implications for Infrastructure
This contrast highlights the importance of climate-adapted infrastructure. As global temperatures rise, countries like the UK may need to reconsider their road construction standards. The UK's Department for Transport has acknowledged that more resilient materials may be needed in the future.
In India, while roads survive the heat, they face other challenges such as monsoon damage and heavy traffic loads. Nonetheless, the comparison underscores how localized engineering solutions effectively address specific environmental conditions.
