Success Story

Based on the past success of the Stress Absorbing Mebrane Interlayer (SAMI) in similar conditions, Miller Paving worked very closely with the Region of York and the design consultant and suggested a double surface treatment with SAMI. This method prevents water ingress from the top and prevents water pumping up to the surface, thus eliminating distortions and extending pavement life. Because of this suggestion, the Region and design consultant agreed that the SAMI was the preferred road maintenance option.  The tender was issued and won for a fraction of the cost of the original proposal and lessened the environmental impact compared to a full road reconstruction.  As of the winter of 2018/19, the road is still well performing.  This initiative won the ORBA Green Award displaying efforts to continuously improve environmental sustainability.

The method used was a typical of a surface treatment operation. After the road surface is swept and cleaned of dust, a light tack coat is sprayed on the road, immediately followed by application of the geotextile. The bottom layer of emulsion is sprayed on top of the fabric, then the bottom coat of aggregate is dropped onto the surface and compacted with a rubber-tired roller. Traffic is allowed to drive on this surface while the adjacent lane receives the same treatment. Allowing traffic on immediately reduces the inconvenience to the travelling public. Emulsion is then sprayed again and the top coat of aggregate is then applied. The Clean Bond Coat fog seal follows thereafter, and traffic is allowed on the fresh surface within 30-60 minutes. At no time does excavation or pulverization of the road surface take place. The project was completed in 3 weeks during July – August of 2015. Selected areas were padded with hot mix or milled to adjust the profile prior to surface treating.

The tender price for this project was under $2 Million. Comparable options that the Owner was considering are shown in Table 1.

Table 1.0: Rehabilitation Options for Old Homestead Road

This situation is typical of rural areas with poor road bases and limited budgets. Option 1 is technically the best option (longest usable life of the road) but is far more expensive than the traffic volumes justify. Option 2 is more conventional, but the pulverization would bring deleterious material closer to the road surface and require more repairs in the near future. Miller’s suggested alternative to these resulted in a further cost savings at construction and in the future, as another seal coat can be applied in 5-7 years to preserve the road in good condition.

Aside from the tendered price of the project, additional savings came from reducing energy consumption. The method used requires 37% less energy per tonne and 78% less energy per square meter than hot mix asphalt (see table 2.0). This treatment used on this project reduces the energy required to heat the hot mix asphalt and the trucking associated with removing and replacing the existing material. Where a long stretch of rural road has a saturated base, full removal and replacement can be cost-prohibitive, while pulverizing would result in deleterious material being even closer to the surface. Future resurfacing with another chip seal or Slurry Seal would still consume a fraction of the energy per m2 that selective resurfacing with hot mix asphalt would. Material use was approximately 3900 tonnes of aggregate and 600 tonnes of emulsion, compared to 21,000 tonnes of a 65 mm hot mix overlay following pulverization, and over 400,000 tonnes of aggregate in a full remove-and-replace.

Table 2.0: Energy Savings of Paving Processes

In summary, using a Double Surface Treatment with Geotextile on this project provided a net benefit in terms of overall sustainability.  The Region of York used this method on two similar roads in their network, both in 2016 and both are performing well today. This is a great example of using the correct treatment on the correct road at the correct time.