Improving Paved Lanes
The Ontario Ministry of Transportation (MTO) is constantly working to produce superior roads for Ontario drivers. In 1997, MTO's Bituminous Section initiated a series of trials with the intent of improving the quality of longitudinal joint construction in the paved lanes of the provincial highway system. The results of these trials have led to a recent proposal for new contract specifications aimed at improving province wide paving standards.
The quality of contractor work at longitudinal joints is a recurrent problem for the Ministry. The compaction (density) of joints is often poor due to the inadequacy of current pavement construction methods. Contractors use pavers to lay hot mix material, followed by roller equipment that compacts the lift of hot mix to appropriate densities to produce a durable roadway. Hot mix that is not paved against an existing lane edge spreads outward in response to the roller pressure - this can result in lower density at edges. Poor compaction can also occur at pavement joints that are confined by an existing edge, due to an insufficient amount of hot mix material at the joint to allow for proper compaction. Over time, the poor quality of longitudinal joints causes accelerated deterioration. Pavement materials ravel away and potholes and cracking form on the surface at the longitudinal joints, resulting in increased maintenance and reduced driving comfort for motorists.
Currently, MTO contracts do not require compaction testing at longitudinal joints within the 250mm strip alongside the paving lane. This often results in the production of substandard pavements.
The 1997 trials represented a new paving initiative, an attempt to prove that quality work could be achieved at longitudinal joints. The long-term goal was the removal of the provision that excluded joint compaction testing from paving contracts.
Four trials of longitudinal joint compaction took place on the surface course of the QEW westbound lanes from Casablanca Blvd. to Fruitland Road. Section one served as a control; longitudinal joints were constructed using normal paving and compaction equipment and techniques. The second section used Joint Match Heater equipment in an attempt to create a better joint by heating the edge of the previously laid pavement. The third section was created with another company's Joint Maker System, using compactor and kicker plates to profile and compact edges, and an electronic edge following device to aid compaction. The final test section used a combination of the Joint Match Heater and Joint Maker systems.
The immediate trial results, obtained from testing core samples, revealed that no one method could be classified as superior. All test sections produced lane edges with exceptional compaction rates of 95% or more. The trials proved that contractors were fully capable of producing quality lane edges without the use of any additional equipment or new techniques. Follow-up investigations, conducted at four and six-year milestones, determined the joints to be performing excellently with no cracking or defects evident.
Since the completion of the trials, a special provision for joint compaction was developed and applied to 12 MTO contracts to date. This provision temporarily altered MTO specifications and presented contractors with incentives and disincentives to encourage proper longitudinal joint compaction. The contractor was paid based on the percentage of the core test results that fell within a defined range. If less than 90% of the results met MTO standards, the contractor's pay was reduced. Bonus pay was awarded if 95% or more of the edge compaction results satisfied standards. A review of these contracts revealed that bonus and full pay was easily obtained on the majority of contracts without any drastic changes made to construction operations. The incentives and disincentives motivated contractors to produce quality pavements that enhanced highway service life.
Based on the success of these contracts, MTO's Bituminous Section has drafted an end-result specification (ERS), which would make incentives and disincentives for surface course joint compaction a standard throughout Ontario for all paving contracts using over 15,000 tons of hot mix. This specification is currently in the final stages of approval, and will be implemented this construction season if obtained.
This initiative to implement a new specification for longitudinal joint compaction represents a progressive MTO effort to ensure the long-term quality and durability of Ontario's highways.