2009 cold recycling on California highways - the pilot project process works.

by Donald Matthews, Pavement Recycling; Chuck Valentine, Valentine Surfacing Co.
Darren Coughlin, Coughlin Construction

Often a new roadway construction technology is not readily accepted by a contacting agency due a perceived failures with the first few projects constructed. These "failures" are often a result of the agency's lack of experience and poorly defined expectations among the parties involved as opposed to problems with the technology itself. In an attempt to successfully implement new pavement strategies and develop consistent expectations, Caltrans developed a pilot project process through the Pavement Preservation Task Group (PPTG). This pilot project process is intended to prevent hasty conclusions and provide all "new" technologies an opportunity to succeed.

Nothing illustrates the success of the process better than the five CIR contracts that were constructed by the State in 2009 (Table 1). Four different general contractors utilizing three different recycling subcontractors constructed these five CIR projects in three different districts. All five CIR projects were ultimately deemed a success, however one of them experienced significant problems. In addition, valuable lessons resulting in the continuing improvments of the CIR specification was the result of all of them. The most significant one is the Caltrans pilot project process calling for Just in Time Training (JITT) and post-construction reviews by the appropriate PPTG Subtask group is a significant means for ensuring ultimate success of a technology.

Caltrans CIR contracts FY 09/10

Contract	Location	Prime contractor	Recycling contractor	CIR depth	Square yards
06-0K6904	Kern SR 33 MP 40.3/45.5	Granite Construction Co.	Pavement Recycling Systems, Inc.	4-inches	79,000
06-0J4404	Kern SR-33 MP 45.5/54.8	W. Jaxon Baker, Inc	Valentine Surfacing Co.	4-inches	136,056
06-0F7404	Kern SR 33 MP 54.8/59.0	Granite Construction Co.	Pavement Recycling Systems, Inc	4-inches	63,702
09-336604	Mono SR 108 MP 9.8/15.1	Sierra Nevada Construction	Coughlin Company, Inc	4-inches	83,200
02-1E9804	Plumas SR 36 SR 12.3/14.0	Knife River Construction	Pavement Recycling Systems, Inc	4-inches	42,342

The importance of good communication and good JITT is clearly illustrated in the three District 6 recycling contracts. The three contracts for District 6 were all on State Route 33 in Kern County. The three seperate contracts ran in series, immediately adjacent to each other. The first CIR contract let, 06-0J4404, was also District 6's first attempt at cold recycling. This was the middle segment of the three projects on SR 33. The project called for four inches of CIR followed by a HMA overlay in some areas and a chip seal in other areas. As part of the mix design process, core samples were gathered by W. Jaxon Baker, the prime contractor, and sent to Asphalt Pavement and Recycling Technology (APART) to conduct the mix design in accordance with project specifications. The mix design called for 3.5% Pass R emulsified recycling agent from Western Emulsions, Inc. as the starting emulsion rate. As it turned out, due to the logistics of the project, this project was the only one of the five CIR projects in the State not to conduct JITT. This also turned out to be the CIR project that experienced the most problems.

Early on in the recycle operation on SR 33, the reycling subcontractor, Valentine Surfacing, recommended a reduction in the amount of emulsified recycling agent based upon the initial laydown performance and appearnce. This reduction was discussed among the prime contractor and Caltrans and it was agreed to reduce the emulsion content to 3% to remain withinthe +/- 0.5% recommendation of the mix design. However, after reducing the emulsion content to 3.0% the recycled material continued to appear to Valentine to be on the rich side and concerns were voiced about the stability of the mix when the weather in that area increased.

The daytime temperatures at the time of the recycling were mostly in the 70° and 80° F range with a few days reaching the 90° F level. Further discussions were held but it was decided to remain at the 3.0% emulsion rate with a concern about veering too far from the mix design recommendaton.

After the roadway was recycled, it was allowed to cure and was released to temporary traffic. During the curing period, temperatures in the area continued to climb into the high 90° F range. At intersections on the project, heavy truck traffic turning loads on to and off of the recycled pavement resulted in rutting and shoving of the cold recycled material. Isolated repairs had to be made to those areas and the project was eventually overlaid and chip sealed.

Granite Construction with Pavement Recycling Systems, Inc. as the subcontractor constructed the other two CIR projects on SR 33. In these two sections of roadway, JITT was conducted with all the parties beginning the project with a good undestanding of the expectations. These two projects utilized the same emulsified recycling agent and the same laboratory completed the mix designs. However, for these projects, the design emulsion content was reduced to 2.5% with one of the projects necessitating the emulsion to be reduced to 2.3% in some areas. These two projects were completed at both ends of the recycled section of SR 33 without experiencing any shoving at the intersections and truck access points.

District 2's CIR project on SR 36 in Plumas County, 02-1E9804, proved challenging in a different way with respect to the distress of the existing pavement and the esisting grades at intersections. However, good JITT provided all parties the clear understanding and the means and measures to handle the project challenges, especially at the difficult turnouts and abrupt stopping grades, General contractor, Knife River Construction and its subcontractor, Pavement Recycling Systems, Inc., made quick work in cold in-place recycling the approximate 42,000-sy project at four inches deep and constructing the 0.15-feet HMA overlay.

Finally, the District 9 SR108 Sonora Junction CIR project, 09-336604, built by Sierra Nevada Construction as the general and COughlin Construction Company as the recycling contractor proved again the value of good communication and defined expectations. This 7,000 feet evaluation Mono County project consisted of 5.5 miles of four-inch CIR with the roadway expanded from 24-feet to 26-feet during the recycling process. A final two-inch HMA overlay was used as the surface seal. The experiences gained by District 9 as relayed during the post-construction review with the PPTG Recycling Subtask Group, resulted in some significant refinements to the CIR specification, By fully implementing the pilot project process, the CIR pilot projects completed in 2009, and the resulting experiences gained by Caltrans provide the State with confidence and it prepares to embark on an aggressive recycling initiave to make the CIR strategy commonplace Statewide.

« Back to News