Incorrect cutting of expansion joints between slabs of concrete is being blamed for the extensive cracking of the bonded concrete overlay along 10.6-mi. of I-40 in Durham County, North Carolina.
The overlay, which was a $44.8 million road improvement project to relieve congestion in the Triangle Park area, was put down in 2003 and 2004. It began cracking in the summer of 2005. General contractor for the project was Granite Construction Company of Watsonville, Calif.
This stretch of road, which should have been good for the next 30 years, is now in need of $18.6 million in repairs.
The North Carolina Department of Transportation (NCDOT) and Federal Highway Administration (FHWA) staff reviewed and reported on the circumstances that led to the distress of the bonded concrete overlay. The final report was submitted in October 2006.
The report concluded that no specific individual was solely responsible for the circumstances that led to the break down of the pavement.
Granite Construction officials did not return calls seeking comment.
Limited Training Blamed for Problems
The report found that problems occurred because the NCDOT pavement experts were not trained properly on the bonded concrete overlay process, a paving method rarely used in North Carolina. In addition, when engineers drafted paving instructions in 2001, they lifted details from a smaller Raleigh-area paving project, mistakenly thinking it was similar to the I-40 project, the report said.
According to the report, a NHI Portland Cement Concrete Overlay course was held Oct. 21, 2003. While the contractor’s personnel were not present at the course, representatives from the private engineering firm hired to perform project inspections did attend the training. It said that at the course, two presentation slides showed that bonded concrete overlay joints must match joints in the underlying pavement and must be saw cut full depth if the depth of the overlay is 4 in. or less. If the depth of the overlay is greater than 4 in., the saw cut depth should be determined by the depth of the overlay divided by three.
Shallow Expansion Joints Used
The I-40 project involved pouring a 3-in. layer of concrete over the two outside lanes of I-40 in both directions. In addition, a third lane, using standard paving methods, was added in each direction.
The concrete layers were supposed to bond as a strong, single layer. The success of the process was dependent on sawing the expansion joints through the full depth of the top layer, making room for the concrete to expand and contract with changes in the weather.
According to the report, I-40 engineers, contractors and private engineering firm inspectors discussed full-depth joint cuts only once —in April 2003, shortly before the bonded overlay work began. NCDOT officials say they gave clear direction that day, but acknowledge that they violated their own policies by failing to put it in writing.
In August 2005, NCDOT inspectors noted that the concrete had begun cracking. After an investigation into the situation, it was found that most of the expansion joints were half as deep as they should have been.
In addition to these conclusions, a review team of state and federal officials also developed a comprehensive list of 21 recommendations to improve project delivery and oversight so this problem would not occur again.
Repairing the Situation
The NCDOT plans to remove the 3-in. layer of concrete from the two outside lanes in both directions —approximately 50,000 tons (45,000 t).
According to Jon Nance, director of NCDOT field operations, removal and disposal of the concrete will be handled by the paving contractor. Contractors typically use the concrete rubble as fill at commercial sites.
Nance said 51,455 tons (47,000 t) of asphalt and micro surfacing will be used on the new road.
The Federal Highway Administration agency paid approximately 80 percent of the original project cost and has agreed to cover a similar share of the new repair bill. Granite has already made approximately $3 million in repairs at its own expense and will not be responsible for any further repairs. The state will pick up the remaining cost.
“The contract availability date for the new paving job is April 2, 2007,” Nance said.
The completion date for the project is Nov. 15, 2007, exclusive of the micro surfacing. It is being let as a design-build contract, which allows the contractor some scheduling flexibility. CEG