Long Life Pavements

Our newest initiative involves rapid rehabilitation/reconstruction of high volume highway facilities. This initiative was the parting challenge of retired Caltrans Chief Engineer Richard Weaver. Approximately 75% of the lane-miles on the California State Highway System were constructed between 1965 and 1973. Some of these pavements are over thirty years old and have exceeded their design life. One of the greatest challenges facing Caltrans and other owner agencies is the reconstruction/rehabilitation of a highway system which has typically carried traffic volumes far in excess of that envisioned by its designers. In addition, the drastic increase in the number of highway users, even through off-peak hours, have driven up the user costs which would occur if any high volume facility were shut down.

The rehabilitation/reconstruction scheme envisioned by Mr. Weaver involves shutting down a small segment of a highway after the Friday night commute, removing the existing concrete slabs, performing the necessary base preparation, pouring fresh concrete, curing the concrete, and reopening the segment in time for the Monday morning commute. Weekend traffic would be diverted to other routes to lessen the impact. Not necessarily all the lanes would be closed, but the capacity of the reduced lane facility would be significantly reduced.

The success of this strategy is largely dependent on orchestration, or getting the resources (i.e. people, equipment, and materials) in the right place at the right time. Timing is particularly crucial with the fast-setting, high early strength, high ultimate strength, hydraulic cement concrete which is intended to give the fresh pavement a thirty year design life. The strength of this concrete is partly derived from chemical admixtures, which cause rapid setting and high early strength. Thus time constraints will include not only the limited haul time from concrete plant to construction site, but also the smaller window of opportunity between the addition of chemical admixtures and the pour.

A task group of pavement designers and researchers from Caltrans, FHWA, and the University of California at Berkeley has been assembled to guide this initiative through design, construction, and monitoring details. The Caltrans Accelerated Pavement Testing Machine (CAL/APT) will be used to conduct field performance trials. Performance models will be developed to guide future designs.

The primary advantage of this initiative is that it provides reconstruction when and where it is most needed. A second advantage is that, if successful, the fresh pavement will not need to be revisited except for programmed rehabilitation and maintenance. Results from this initiative may drive pavement policy for years to come.

The disadvantages of this initiative are primarily inconvenience to the highway users, diverted traffic and traffic delays.