Why Indian roads crumble every monsoon: the science

Monsoon rains wreck Indian roads through four distinct mechanisms, the Central Road Research Institute (CRRI) explains. Water strips the bitumen coating from stone chips, softens the ground beneath, builds up hydraulic pressure that hollows out layers, and combines with the extreme summer heat that softens the binder and lets tyres rut the surface. India's highway rulebook (Section 500) requires anti-stripping additives only when the contractor's chosen stone is known to bond poorly, leaving wide discretion at field level.

Stripping is the primary cause: many Indian stones, especially granites and quartzites, are water-loving and bond better with water than with bitumen. Anti-stripping additives such as hydrated lime can fix the issue, but the contractor decides when to use them. The cycle of summer softening and monsoon saturation then fatigues the pavement from opposite directions across the year.