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5 posts categorized "Worker Safety"

October 26, 2016

SCDOT & Sloan Rebuild I-85

Sloan I85 recapAdapted from "Fast Fix for Failing Freeway" by Tom Kuennen for Asphalt Contractor

A unique design for warm mix asphalt (WMA) enabled the South Carolina DOT (SCDOT) and its contractor, Sloan Construction, to get a mid-winter start early in 2016 on urgent reconstruction of failing I-85 in the northwestern corner of the Palmetto State. Because WMA can be compacted to required density at lower ambient temperatures, it can lengthen the paving season by enabling winter paving.

The warm mix additive also served as a compaction aid that permitted Sloan to quickly get specified density on twin lifts totaling nine inches, in time-limited night work, to avoid severe penalties for failure to reopen the highway in time for the morning rush in the busy Spartanburg—Greenville corridor.

On this project, in a single one-night shift, as much as nine inches of delaminated, failed pavement would be milled, and the warm mix additive Evotherm® allowed placement of two, four and one-half inch lifts in that single shift, rather than the three, three-inch lifts that would have been required under standard specs, making it impossible to open the pavement by morning rush hour.

The I-85 work was taking place between mile marker 56 to 68, milling out left and center lanes from five to nine inches, and for the right hand lane, milling out 10 inches and putting nine inches back. 

"The DOT realized that, in starting the project last year, the structure of the road didn't hold up the way they wanted it," said Dennis Ayers, senior project manager for Sloan North Region. "They re-let the contract to put in a new base course and reconstruct the road to handle the traffic."

"When we first started we were going to do a two or four inch mill-and-fill," said Chad W. Hawkins, P.E., C.P.M., state materials engineer, SCDOT, Columbia. "But some of the milling process got down into delaminated areas, and that's when the project was put on hold, and we thought 'What do we do now?'".

The pavements in this section were constructed in the 1950s and 60s, so finding out what went wrong is problematic. "Realistically, our two, three and four inch mill-and-fills over the last 50 years have caught up with us," Hawkins said. "It's time to do a major reconstruction, and that's what were finding on a lot of our interstates. We're having to do more than put a four inch 'band-aid'."

On a night in the northbound lanes in July 2016, crews were milling out 10 inches of failed pavement, and were replacing it with two, four and one-half inch lifts of leveling course pavement. They paved 1,000 feet in a single night shift, leaving room for the final driving course.

There, Ingevity's Evotherm enabled Sloan to get density on the first lift, and place the second four and one-half inch lift right on top of the first. Both lifts cooled rapidly to permit timely opening to traffic on the second lift.

Target densities were being met on site and in test strips. Also, Sloan was getting 93 percent density on the cold longitudinal joints, which go down nine inches. "The job is going well," said Todd K. Carroll, P.E., resident construction engineer, SCDOT, Spartanburg County. "They are able to produce a lot of mix every night, very efficiently. We've had a good project so far."

Read the full article in Asphalt Contractor Magazine here.

 

February 17, 2014

Czech Repulbic's Blanka Tunnel

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The Blanka tunnel in the Czech Republic is the longest urban motorway tunnel in Europe. Evotherm WMA technology is being used to pave the 6-kilometer tunnel in order to achieve compaction while minimizing fumes in the confined space. The tunnel is part of the City Ring Road and will eliminate through traffic from the UNESCO historical center

The typical cross-section of pavement in the tunnel consists of a membrane on the concrete substrate of the road, followed by three asphalt mix layers: 20-mm asphalt for very thin layers, 85 mm asphalt binder course, and 35-mm stone mastic asphalt wearing course. All three asphalt mixes were made from highly modified SBS binders. Laboratory testing showed the Evotherm WMA mix designs to have improved water resistance while maintaining rutting resistance. 

Manufacturing temperatures at Eurovia's Klecany plant for all three mixes were approximately 145 C (293 F), or 35 C (63 F) lower than typical for the use of a PMB 25/55-60 binder. During whole day production of WMA, gas consumption for heating of aggregate decreased 25%.

Temperatures during lay down ranged from 130-135 C, nearly 40 C (72 F) below what would have been the case with similar hot mixes. The lower temperature dramatically reduced the asphalt fume emissions, especially with such modified binders, and greatly improved working conditions within the tight confines of the tunnel.

The MWV team was excited to validate for the first time in the Czech Republic and in the very prestigious location of the Blanka Tunnel the many technical advantages of the Evotherm WMA technology.

 

Author: Claude Giorgi

May 31, 2011

Cutting Paving Time at Echo Summit

Caltrans made a historic decision in allowing a California contractor, CC Myers, to close US 50 over the famed 7,382 foot Sierra pass called Echo Summit.  The city of South Lake Tahoe depends on this highway for its commercial and tourist needs.  MWV Asphalt Innovations with their partner, Telfer Oil Company, provided Evotherm on a Caltrans project to address cold weather paving concerns with a 90 minute haul and to reduce overall road closure time.

CC Meyers had two weeks to conduct a major reconstruction of safety walls and pavement before the Memorial Day Holiday. A snow storm dropped over a foot of snow on the project site just before the start. Finally, the clouds parted and allowed time for Don Garcia Paving to plow a foot of snow prior to milling of the surface. Teichert Aggregates produced the ¾” mix containing Evotherm in the town of Truckee, CA, over 90 minutes from the project location.  The State suggested that the use of WMA as a result of anticipated cold morning conditions with lows in the upper 20s.  

After a trek around the eastern shore of Lake Tahoe, the first trucks arrived onsite. The mix was windrowed on the milled surface and placed in a single 3” lift.  Don Garcia Paving achieved density with two passes even with mix temperatures behind the screed of 210F. The sheer rock face and over hanging rocks were a safety concern. Too much vibration could cause rocks to fall onto the paving operations. Achieving the necessary compaction during breakdown allowed the remaining rolling operations to be conducted in static mode and minimized rock falls.

Starting the paving operation in the early morning and completing the paving long after the sun had set, allowed Don Garcia Paving to complete paving in one day instead of two days.  CC Meyers reopened US50 to traffic two days ahead of schedule (Every Day Counts!). Evotherm once again showed its ability to be produced, hauled, and placed in low ambient temperatures.  How can you use Evotherm to improve your operations?

 
Author: Brandon Milar

May 03, 2011

Tunnel Time

The Jiaozhou Bay Tunnel paving trials with Evotherm WMA were completed last month. Evotherm exhibited good performance during road paving and minimized fumes during the tunnel application. The trial section is a 7 kilometers of polymer modified asphalt. The owner plans to pave the whole tunnel using Evotherm WMA. The tunnel project in Jiaozhou Bay in Qingdao, Shandong province is the second submarine tunnel in China. The project is a city tunnel that accommodates six-lane, two-way traffic.In a tunnel, the combination of hot mix asphalt fumes and high temperatures caused terrible working conditions. The lower temperatures improved the construction conditions greatly. The mixes made with Evotherm also achieved roadway densities more easily than the conventional HMA, creating a better quality road.

Hot-mix asphalt paving
Hot-mix asphalt paving

Tunnel-picture-2
Paving with Evotherm warm-mix asphalt

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