ForConstructionPros.com

Any cold joint is a huge problem,” says Mick Carricaburu, paving superintendent of Skanska USA Civil West, Riverside, CA, acknowledging what every paving contractor knows.

The reason is simple: As hot mix asphalt cools it becomes less pliable, making compaction more difficult. From the time it takes a paver to start a paving pass, complete the pass, and then return to begin a new adjacent pass, the mat is cooling. And even though the roller is working closely behind the paver, by the time the paver begins its pass up against the previous edge, that edge has cooled. And when an edge is exposed for even longer times, it becomes difficult to achieve proper density.

According to the Asphalt Institute’s The Asphalt Handbook, compaction density needs to be at least 92 percent to be effective, and contracts often specify a minimum density that must be attained. Contractors following standard hot mix placement and compaction procedures can meet that requirement. But if acceptable density is not achieved, the joint because a fault in the pavement, an entryway for water to work its way into the base and subbase, the first step in pavement deterioration.

So what can a contractor do when faced with a job where the density requirements are not only greater, but the penalty for not achieving those density goals is potentially very damaging? Such was the case with the job Skanska took on paving the reservoir at Tehachapi East Afterbay, near Gorman, CA.

Given that the project was a 71-acre reservoir, designed to hold water from the California Aquaduct, California’s Department of Water resources placed significant emphasis on achieving density - not only of the 6-inch mat but of all the joints in the 100,000-ton job. Specifically, if joints weren’t compacted to the required density the reservoir would leak, so Skanska had little margin for error. The state’s specification allowed no deviation from its density specifications.