In January 2000, Wirtgen opened discussions with Caltrans to explore the possibility of developing a Cold Foam In Place Recycling project. Caltrans had identified a section of highway 20 that was due for rehabilitation which is the ideal candidate for a recycling project.
The standard design procedures requires an asphalt rehabilitation of this road with a total of 708mm of various asphalt layers to be constructed. By using a recycling principle the existing material will be stabilised to a thickness of 225mm followed by a 46mm asphalt layer. Not only are the construction time reduced by using this method, but the amount of imported “virgin” material used during construction is limited to only the final asphalt layer that was constructed. An additional benefit is that the existing subgrade layers will not be disturbed.
The construction of this road was done in four phases. Phase one entailed the recycling of the westbound lane by using two Wirtgen WR2500 recyclers in echelon to stabilise the existing pavement with 2.5% foamed bitumen. Phase two entailed the construction of the asphalt layer on the newly constructed BSM layer. Phase three and four were similar to the first two phases, but for the eastbound lane.
Prior to recycling with foamed bitumen this section was a continual drain on maintenance capacity, since completion there have been no maintenance requirements. The road owner is completely satisfied with the recycling/rehabilitation process. The is no evidence of any pavement distress after an estimated 4,350,000 vehicles (20% trucks) used this section of highway 20.