Up against a looming implementation deadline, Caltrans and the asphalt pavement industry are stepping up efforts to hammer out an agreement over a "Superpave" specification that will replace the current asphalt specifications that rely on outdated testing procedures.
In 2011 Caltrans announced that it was going to adopt the Superpave mix design method effective July 1, 2014. The current "Hveem" mix design method was originally developed in the 1930s by Francis Hveem, an engineer with the California Department of Public Works, Division of Highways, as Caltrans was known at the time. The new "Superpave" name is derived from "SUPerior PERforming asphalt PAVEments," and was a state highway agency initiative of the 1990s. California and Nevada are the only states that have not fully implemented Superpave.
Superpave is a performance-based suite of test procedures for materials selection and design of asphalt mixes. The highly focused, product-oriented research program was funded by the states through the American Association of State Highway & Transportation Officials (AASHTO) and administered by the Strategic Highway Research Program (SHRP). It is a comprehensive method of designing asphalt mixes tailored to specific and unique performance requirements governed by climate and traffic. One aspect of Superpave, the performance-grade (PG) system of classifying binders, has already been implemented in California.
Caltrans has said its goal in transitioning to Superpave is to help the state adapt to changing environmental conditions, new binder grading systems and changes in traffic patterns. In moving to Superpave, California will also capitalize on the many national research efforts undertaken in support of the Superpave mix design methodology.
To begin the Superpave implementation process Caltrans held several meetings with its Industry counterparts to discuss the implementation plan. In early 2012 Caltrans formed a Superpave Subtask Group (STG) under the auspices of the Caltrans-Industry Rock Products Committee. Initial Superpave implementation activities began with a draft specification to be administered on "pilot projects." Following a short review period, the STG identified 105 areas of concern. After further review and discussion, the initial list of concerns was condensed to 85. The first working Superpave STG meeting was held Feb. 12 in Sacramento with subsequent monthly meetings alternating between Northern and Southern California.
Because a number of the Superpave provisions are untested, industry stakeholders have continually expressed a high level of concern regarding the risk to bidders and holders of contracts, industry has expressed concern about the risks in bidding and building these projects. Conceptually, contractors can "try out" the new specifications prior to bid. However, in reality some of the Superpave provisions impart more stringent material requirements that may necessitate significant changes to the material processing and plant production.
Those challenges notwithstanding, collaboration between Caltrans and Industry has been good resulting in considerable progress since the initial STG meeting, says Tony Limas of Granite Construction, committee co-chairman. As of August the current list of concerns has been reduced to 14 issues. The department has pledged that final disposition of the remaining issues will be revisited pending data collected from the pilot projects. It is anticipated that regular Superpave projects will be out to bid in January to meet the July 1, 2014 implementation date. With only limited data from pilot projects received so far, Caltrans and Industry are working feverishly to gather and analyze the data as quickly as possible to put the finishing touches on a Superpave specification by the end of the year.