Adapt, Improvise and Overcome

The westbound bore lanes were to be closed from 9 p.m. Sunday, Sept. 10 through 9 a.m. Friday, Sept. 15 and again for this duration the week of Sept. 17 through Sept. 22. "The general contractor had some additional utility work in the westbound bore, so we had extra time," explains Adams. "We are going to be tight with the other tunnel."

The contractor faced stiff lane rental fees if these parameters were not met. The graduated fees start at $400 for the first hour and increase to $3,200 for the fourth hour and every hour thereafter. A maximum rental of up to $70,000 per day, per lane could have been assessed.

Laying a high quality mat was just as critical as meeting the time deadline. In addition to laying a mat void of segregation and flushing, Pavetec was required to meet the state's Category I Continuous Half Car Roughness Index (which measures both left- and right-hand wheel paths) of 135 inches per mile with no blanking band.

Original plans to use the contractor's existing 8-foot paver were scrapped in favor of a heavier, higher production 10-foot paver. Terex Roadbuilding supplied a Terex Cedarapids CR562 rubber track paver to help lay a smooth mat at the 13-foot paving widths. The Stretch 20 electric screed provided initial compaction of the tender mix.

"Giving the crew a new paver for a high profile project isn't the most ideal situation, but Pavetec's guys quickly became comfortable with the paver's operation," says Vince Egan, district manager for Terex Roadbuilding.

In order to help establish continuous, non-contact paving and ensure delivering a homogeneous mix to the paver, the Terex Cedarapids CR662RM RoadMix MTV was also added to the train. The RoadMix has a 16.7-ton receiving hopper that, when combined with the paver's hopper capacity, offers significant surge capacity for establishing non-stop paving. "Even with the low clearance inside the tunnel, we were able to use the RoadMix due to its 9-foot 2-inch operating height," adds Egan.

Inside the CR662RM's receiving hopper are four counter-rotating augers — grouped in sets of two — that continuously reblend the material. This helps to combat material segregation resulting from the storage, loading and transport stages.

More importantly for this project, the remixing process prevents thermal segregation, providing more uniform mat temperatures. This allowed the rollers to more readily reach specified densities, which ranged from 93 to 97 percent of the SMA mix's minimum specified gravity.

Overcoming trucking issues

While Pavetec used high production paving and compaction equipment for the project, the paving train would not be as effective if there weren't enough trucks to deliver mix to the site. Egan worked with Rusty Evans, transportation manager for Pavetec, to map and time the truck route to determine the right number of trucks.

"The site was about 17 miles from the plant, and it took approximately 40 minutes under ideal driving conditions," says Evans. "We concluded that 16 live bottom trucks would be necessary to establish continuous paving."

Pavetec could only use live bottom trucks inside the tunnel because of the low clearance, so Evans lined up the 16 trucks for paving the westbound bore the week of Sept. 17. On the first day of paving, however, there was an obvious problem.

"Only nine trucks showed up to deliver mix to the site," says Olson. Not only did this lead to long wait times between truck loads — poorly employing the production capacities of the MTV and paver — it put meeting the Friday, 9 a.m. deadline in jeopardy.

Key personnel from Pavetec, American Civil Contractors and Terex Roadbuilding met after the first day of paving to discuss possible solutions to the truck shortage.

"We decided to split up the paving train in order to increase the number of trucks delivering mix," recalls Egan. "This would use the equipment more efficiently and improve paving production, so Pavetec could get the job done on time."

The RoadMix MTV was moved outside the Eisenhower Tunnel, so Evans could add seven readily available end-dump trucks to the cycle.

"After a live-bottom truck delivered its load from the plant, we staged it by the conveyor of the MTV," says Olson. Pavetec then used the RoadMix to transfer mix from an end-dump truck to the live-bottom truck, so it could go back into the tunnel to deliver more asphalt to the paver.