The available surface friction between tarmac and tyres is a critical road-building parameter. It is determined according to the road’s designated speed and expected traffic load, so the asphalt formula used for, say, Kranji Way is very different from that of Kranji Expressway.
A few years ago, Samwoh was tasked to formulate a new asphalt with some peculiar specifications. It’s a high-performance grade with very high friction properties. The company eventually labelled it the “F1 Asphalt”, and continues to provide the material whenever there is a requirement to resurface the Marina Bay Street Circuit just before the Formula One race weekend.
On the subject of road maintenance, Samwoh’s Dr Lee told us that the company works closely with the Land Transport Authority (LTA). “We own a series of highly specialised laser and sonar equipment to analyse surface thickness, transverse and longitudinal deflection, 3-D profile, friction coefficient and wear pattern. The data we acquire is provided to the LTA for their input into the Pavement Management System or PMS”.
Thanks to the PMS, Singapore’s islandwide road maintenance is scheduled and carried out before the road surface wears to a point where holes and ruts begin to appear. “Corrective road maintenance is an extremely rare occurrence in Singapore,” added Dr Lee.
The road’s “Wearing Course” must be removed prior to any resurfacing. Those machines we often see with a long conveyor belt in front, following a tipper truck and spewing waste into it, are called milling machines. They grind off only the top of the blacktop, so to speak, leaving the other layers as they are.
All the material that is ground and removed isn’t dumped as waste – instead, it is reused as aggregate in new asphalt mix. A mixing-and-batching plant prepares the premix according to the required specifications for the particular road being repaved. Samwoh’s latest asphalt factory is designed to reuse the milled surface from roads undergoing refurbishment.
The final task is for the road-laying machine to fill up the milled sections with a fresh, clean, black and grippy “Wearing Course” for a smooth and comfortable ride on the road.