CANTON, S.D., U.S.A, For the City of Atlanta, what happened on the evening of Thursday, March 30, was the nightmare scenario. Fire blazed out of control underneath a busy elevated section of Interstate 85 near the Downtown District. Intense flames burned so hot that the fire weakened part of the northbound lane structure, causing it to collapse and severing the artery used more than 243,000 vehicles per day.

“It is one of the most critical interstate sections near downtown Atlanta, and the project needed to be started immediately and finished quickly,” explains Dan Garcia, president of C.W. Matthews, Marietta,Ga., the contractor selected for the reconstruction project. “Originally, it was thought that only the collapsed northbound span required replacement, but the inspection unveiled six damaged spans for replacement – three northbound and three southbound.” With both lane directions closed to traffic, vehicles were quickly rerouted to the nearby Buford-Spring Connector and other routes. Georgia’s Governor worked with Federal Highway Administration officials to obtain a special waiver to circumvent the typical bid-letting process. Instead, the Georgia Department of Transportation called on local contractor C.W. Matthews with whom the department had a long and successful relationship.

While working out the details with the Georgia D.O.T for the eventual U.S. $11.6 million contract to reconstruct the damaged spans, C.W. Matthews’ crews began removal of 13 million pounds of debris to make way for the new construction. The final bridge span reconstruction contract included a June 15, 2017 deadline, a mere 75 days after the spans collapsed, and up to U.S. $3.1 million in incentives to get the project completed earlier.

Need for Speed

With so many people impacted by the I-85 closure, all eyes were on C.W. Matthews’ crews to safely and efficiently complete the repairs, so Atlanta could get back to normal. “We were just doing our job,” comments Adam Grist, vice President of structures for C.W. Matthews, “and initially we didn’t recognize how high-profile this job was.” Everything had to perfectly fall into place for the project to be completed on time. Due to the project’s importance, any mishap or delay would be magnified exponentially, as C.W. Matthews prepared to com press a typical 10- to 12-month project into a contracted time of just over two months. The biggest obstacle, according to Garcia, would be getting the concrete beams for the bridge reconstruction. “These beams aren’t just sitting around in inventory,” explains Garcia. “They had to be cast, and we needed 61 beams. The supplier started casting the Monday after the collapse (April 3) and did an excellent job delivering them on time.” The lane closures not only affected local traffic, but it also impacted material delivery to the project site. Grist mentions that special efforts were taken to expedite delivery of items like the concrete beams. “We had police officer escorts for beam shipments,” he says.

C.W. Matthews lined up crews to work around the clock for the project. “We employed two 12-hour shifts,” says Garcia. Communication was key to the success between the day and night crews. “We held daily status meetings between the day and night crew leaders to make sure we were on schedule and to help us to accommodate any delays encountered,” adds Grist. They started with rebuilding the support structure for the deck while the beams were being cast. “We built four intermediate piers, 13 columns and four caps,” says Grist. “To save construction time, we used an accelerated concrete with fibre additive to gain the design compressive strength in 24 hours.” C.W. Matthews maximized virtually every time-saving opportunity conceivable to quickly reopen I-85. For concrete delivery, supplier ThomasConcrete reportedly delivered a majority of the concrete using front discharge mixer trucks, which included a fleet of Terex Advance trucks. “Because front discharge mixer trucks are driven right into the jobsite, offer a high discharge point and drivers discharge the load from inside the cab, material is unloaded faster than with rear discharge trucks,” explains Mark Aubry, director of customer engagement strategy, sales and service organization for Terex Advance. Even though C.W. Matthews has its own fleet of crawler cranes, the company rented a 700-tonne (800-ton) capacity class Terex AC 700 all-terrain crane from Southway Crane & Rigging of Atlanta to save time. “The all-terrain crane sets up quicker and is more mobile than our crawlers,” explains Grist. “We used it to set 40 large beams, and we used another 500-tonne (550-ton) class rental crane to set the other 21 beams.”

Alternating Deck Pours

Even with deck paving, C.W. Matthews looked to save every minute possible. Project managers devised a plan of alternating pours between the southbound and northbound lanes using a special concrete to compress nearly two months of paving into just 12 days. “We used a 3,500 psi Georgia D.O.T Type 3 concrete to speed up cure time for reaching compressive strength,” explains Grist. “It achieved design strength in 36 to 48 hours and included a shrinkage admixture to prevent cracking.” C.W. Matthews had not used this type of concrete prior to the I-85 project, and there was some concern during the first pour. However, “It finished similar to that of regular concrete, so there were no issues,” continues Grist. Deck width for both bridge structures measured 24.3 m (79-ft, 7.5 in) across, allowing each to accommodate five vehicle travel lanes. The paving plan called for a total of six segmented pours, three each for the northbound andsouthbound structures. With the smallest pour of 144.5 m3 (189 yd3) and the largest being 235.5 m3 (308 yd3), deck pours averaged roughly 191.1 m3 (250 yd3), accounting for roughly 1,146.8 m3 (1,500 yd3) of the project’s total 1607.9 m3 (2,103 yd3) of concrete. C.W. Matthews used two of its Terex Bid-Well automatic roller pavers to finish the deck, a 3600 paver for the northbound span and the 4800 forthe southbound. The 3600 paver was purchased in 2016, but the 4800 included components from two pavers, both more than a decade old. “One machine was purchased in 2002 and the other in 1995,” mentions Larry Eben, regional sales manager for Terex Bid-Well. Some contractors may be hesitant to use such a seasoned paver on a high-profile, time-sensitive project like I-85, but Grist explained there was no concern. “We have poured tens-of-thousands of yards of concrete with the 4800 paver,” he says, “and it has been well maintained and performs well.” The 4800 was selected specifically for the southbound bridge due to its trapezoidal design. “The first pour with the 4800was made square to the centreline joint,” mentions Grist. “For the second span, we had to adjust the machine to pave at the bridge’s 55° skew angle.” Eben adds, “Crews added a 3.7-m (12-ft) and a 1.8-m (6-ft) segment the frame to extend machine length for paving at the skew.” Both the 3600 and 4800 machine widths were set to 25.6 m (84 ft) when paving square to the centreline. Offering 26.2- and 35.4-m (86- and 116-ft) standard maximum paving widths respectively, both the 3600 and 4800 pavers easily accommodated the square width. When paving at the skew, however, paver length reached 31.1m (102 ft). That’s where having the larger 4800 paver paid off.

C.W. Matthews added transition inserts to the machine’s frame for paving at the skew, which expanded frame height from 111.8 to 167.6 cm (48 to 66 in) at the centre to improve rigidity. “We were getting to a long machine span, so it was good to have the inserts to prevent deflection,” says Grist. “It took less than four hours to add the extra frame components. Both pavers set up quickly.” Deck paving started the evening Monday, April 24, with the first pour of the northbound span. Concrete was delivered to the deck via a 46-m concrete boom pump. To accommodate the faster curing time with the concrete, C.W. Matthews added four finishers to the crew. “On a typical bridge job, we would use a 16- to 18-person crew. On this one, we had a 20- to 22-person crew,” says Grist. Alternating between the northbound and southbound lanes, pours continued on Wednesday, Saturday, Sunday, Tuesday and finally Friday, May 5, and incredibly there was only one pour postponed due to weather. All bridges were built to a 4.5 percent super elevation without a crown, so when it came time to pave at the skew angle, the 4800 paver and its paving carriage were adjusted to the skew without the need of Terex Bid-Well’s skew bar kit. By Sunday, May 14, C.W. Matthews had completed the finishing touches on both the northbound and southbound spans of I-85, and they were reopened to traffic a full 32 days ahead of schedule. The contractor’s amazing efforts resulted in the completion of nearly a year’s worth of work in just less than 45 days. “I am so proud of our team and excited about the outcome,” says Garcia. “I am proud of our crews’ work and am even a bit surprised as to what was accomplished so quickly,” Grist adds. “This project showcased our company’s skilled expertise. It also shows just what can be accomplished in a short period of time when building an outstanding working partnership between all parties involved.”