Bitumen spray sealing looks simple from the roadside, a truck sprays hot binder, another spreads stone, a roller follows. In reality it is a precise piece of timing and temperature control, and it is the reason so many of our rural roads survive the Gippsland winter.
The seal itself is a thin waterproof membrane. The sprayed bitumen binds to the pavement and locks in a single layer of aggregate, keeping water out of the underlying base. Keep water out and a pavement can last for decades; let it in and the base softens, the surface cracks and the whole road starts to fail.
Getting it right means matching binder application rates to the aggregate size, reading the pavement temperature and sealing in the right weather window. Done well, a spray seal buys years of service life for a fraction of the cost of a full asphalt resurface, which is exactly why it remains a workhorse of regional road maintenance.