Bad cement is the reason why many asphalt roads crack prematurely, city councillors were told Tuesday.
Specifically, road director Dave Shelsted said it's the quality of oil used in the asphalt cement that has failed on roads, particularly in southwestern Ontario.
They did a trial on a road in Timmins, he said, which determined the problem was with the cement. But there are several reasons road asphalt cracks prematurely, Shelsted said.
It depends on how many heavy trucks use the road for mining and logging transport, and the effect of extreme temperatures in the North.
“Unfortunately, we see a lot of this in Greater Sudbury,” Shelsted said. “And with our climate, we see extreme temperatures.”
There are good reasons to modify asphalt cement, he said, which makes up five per cent of the asphalt laid on roads. Adding bitumen can improve stiffness to increase rut resistance and cracking, and by improving elasticity, the road can resist fatigue cracking.
“In some instances, modifying the asphalt cement is beneficial,” Shelsted said.
But when used motor oil is used because it's cheaper, that's when problems occur. So the province has mandated a new mix formula to ensure the consistent quality of Ontario's roadways.
“Recently, for asphalt cement, there have been a lot of changes,” Shelsted said. “Right now, no waste oil can be used to modify asphalt cement.”
The city conducts quality control tests to ensure contractors are following the rules, he added. And the city now has a warranty on all roadwork.
“We've implemented that for all contracts in 2017.”
He said a fully reconstructed road with new asphalt should last 15-20 years, depending on traffic. Surface treatment – so-called shave and pave – will last five to seven years.
