To further optimize product quality, the City has mandated the use of Portland cement to increase retained stability and decrease the potential for post-construction raveling caused by weather since 2009. Although this mandate provided a significant increase in product quality, the City experienced many challenges with public vehicles traveling through the cement applied, causing many claims to clean vehicles, and complaints of fugitive dust. Again the City worked closely with the contractors to ensure that gaps between the cement spreader and the recycling train were kept to a minimum to avoid such claims and mandated the use of a spreading device that would minimize dust emissions. In addition, the City has been very active to improve curbside compaction through various compaction methods and auxiliary equipment against curb faces which has eliminated cracking against the curb.
Lowering of maintenance holes and valve chambers within this process initially seemed overwhelming but as both the owner and contractors became more experienced, the process went much smoother. Initially the contractors had many issues with hitting the plates covering the manhole cavity, therefore filling it with pulverized material causing sewer and water main plugs necessitating immediate cleaning and disposal. Paul’s team was able to embrace these challenges through his determination and was able to accept the growing pains of implementing a new process which ultimately led to further growth of the program. Although the quantity of FDR performed by the City varies from year to year depending on budget and scope of work, the average amount of FDR with Foamed Asphalt Stabilization is approximately 82,500 m2 (98,700 yd2) since 2002.
With Paul’s vision, the City of Markham has recognized the need to design the pavements according to the climate, pavement structure, and intended traffic and tracks the performance of strategies to determine the effectiveness of treatments utilized. Through their regimented asset management software, they determine which roads are suitable candidates for rehabilitation by performing pavement evaluations on each road section every two years. Once a pavement falls below a predetermined threshold, the asset management division provides mapping to the Operations department that identifies OCI (Overall Condition Ratings) to each street within the City. The Operations Department then reviews the map and past construction histories and prioritizes them. They have learned through the years that ARRA Award Winners
the software output needs to be confirmed with field evaluations to ensure that the software is predicting pavement performance accurately and ensure they are spending allocated funds appropriately. The City utilizes pre-engineering data and Annual Average Daily Traffic (AADT) volumes to assess the structural capacity of the potential candidates and confirm the feasibility of in-place asphalt recycling. The City then hires a consultant to perform a pavement evaluation and subsequent design considering all of the potential rehabilitation strategies such as FDR with Foamed Asphalt, and mill and overlay, with and without the use of Stress Absorbing Membrane Interlayer.
Markham reports that one of the added benefits of in-place full depth asphalt recycling is the ability to enhance a roadway’s structural capacity or Granular Base Equivalency (GBE), without the need to place additional lifts of hot mix below the wearing course. The placing of additional lifts of hot mix is not only very costly, but may also necessitate the reinstatement of concrete curbs to a higher elevation. The City has successfully employed FDR with Foamed Asphalt Stabilization on community center parking lots, local residential, local collector, and on both two-lane and four-lane major collector roadways with an AADT ranging between 500 – 15.
In 2012, the City performed nearly 40,000 m2 (47850 yd2) of FDR with Foamed Asphalt Stabilization.Prior to performing the in-place recycling process, structures such as maintenance holes, valve chambers, and valve boxes are lowered to sufficient depth to allow the recycling equipment to pass over without interference. Once these adjustments have been made, the area is pre-milled to the depth equivalent to the Hot Mix Overlay depth. Typically the City utilizes 50 mm on residential and collector roadways and up to 90 mm on arterial roadways, all according to the pavement design.