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As seen through a wood structure erected for
the occasion, workers with the contractor, Kraemer North America, synchronize
their efforts with the Bidwell screed machine during the 14-hour effort Sept.
13-14 to level the concrete for the new interstate bridge over Cimarron
Street/Highway 24. The work covered an area 80 feet wide and 359 feet long.
14-hour concrete pour prepares first lengthwise 'half' of new Cimarron/I-25 bridge
A worker uses a long board Sept. 13 to check
the concrete that's been poured for the new interstate bridge's roadway over
Cimarron Street/Highway 24.
Westside Pioneer photo
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The work was accomplished by close to 100 workers with Kraemer North America - the contractor for the $113-million interchange replacement project by the Colorado Department of Transportation (CDOT) - in a non-stop endeavor between 3 p.m. Sept. 13 and 5 a.m. Sept. 14.
Because of the possibility of concrete dripping down, Cimarron Street (below the bridge) was closed for the night in both directions, once the pour got near to actually being over the roadway itself.
According to Don Garcia, deputy project manager with CDOT consultant Wilson & Company, the area of concentration covered a bridge area 359 feet in length and 80 feet in width, with the concrete needing to be leveled at 9½ inches high.
In all, the project required 760 yards of concrete. Putting that in perspective, a single concrete truck mixer holds a load of 7 yards, Garcia noted. So the pour needed more than 100 mixer loads.
During the work, the trucks could be seen lined up on a closed-off area below and to the west side of the bridge, where a machine attached to each truck in turn pumped its load upward through a line arching over and down to the bridge deck. The overall concrete travel distance was 183 feet, Garcia said.
A worker directs the flow of concrete from a
hose onto a cross-hatch of 3/4-inch rebar.
Westside Pioneer photo
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The pour used the Bidwell system, which, according to the Terex Bid-well website, was developed by South Dakota bridge contractor “Tex” Bidwell in 1961 and has since become the industry standard. As seen in photos with this article, a Bidwell consists of metal units bolted together as needed to match the width of a bridge. One type of Bidwell unit, called a “screed,” has an operator standing on top controlling mechanical equipment which handles the lion's share of the concrete-leveling chore.
During the Sept. 13-14 Cimarron/I-25 pour, the pumped concrete came out of a wide hose, whose steady flow was directed by a worker slogging at times through the concrete itself near the Bidwell. Slogging with him - and like him wearing high rubber boots for the purpose - were numerous fellow workers, who helped to distribute the liquid mass as evenly as possible to the 9 ½-inch height before it solidified. They were using shovels, hand-held leveling devices and vibrating tools that “assure the proper consolidation of the concrete around the rebar,” Garcia explained.
At 80 feet, the now-concreted bridge represents just over half of the planned, final interstate width over Cimarron. The rest of it, to be completed in 2017, will add 71 feet to the width, making it a total of 151 feet across. The 80-foot side has been called the "southbound" bridge (for ease of explanation), because at project's end it will carry the southbound lanes (and a little bit more). However, when engineers discuss the construction as a whole, they say that the coming 71 feet will be "added" to the 80 feet, meaning that technically the southbound and northbound sides will all be one big bridge.
Roadwork is still needed on a short stretch south of the bridge to link up with a new I-25 segment that was realigned between Cimarron and the Nevada/Tejon interchange this summer.
What will happen in October (date not yet specified) is that the 80-foot bridge portion and the southbound side to Nevada will start temporarily carrying both southbound and northbound traffic. It will be a tight three lanes each way, with narrower lanes and shoulders, but as Garcia explained, the project had to be done this way because the bridge couldn't be built any wider while the old northbound bridge at Cimarron was still handling traffic. That bridge can now be taken down. The demolition will happen later this year, the schedule shows. Built in its place, sometime in 2017 will be the new bridge's other "half."
Mark Bilby, a structural engineer with WSP Parsons Brinckerhoff, Inc., is quoted in a CDOT press release about the unique lengthwise stability of the new bridge. "There aren't many bridges in Colorado like the new I-25 bridge at the Cimarron Street/US 24 exit," Bilby said. "It's a highly efficient bridge for the size of girder being used, [with] three girder segments of varying lengths, that when spliced together with post-tensioned cables, creates an efficient two-span bridge... The pre-stressing and post-tensioning processes maximize the length of the bridge span and eliminate the need for another pier, which would otherwise need to be constructed in the middle of Cimarron Street.”
Westside Pioneer article
(Posted 9/16/16;
Transportation:Cimarron/I-25)
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Attached to a cement truck (not seen from this
angle) the concrete pumping rig at the lower left uses an arrangement of connected
pipes arching over and down to where the concrete flows from a hose directed by
a worker standing on the new bridge. The overall travel distance is 183 feet. At far
right is deputy project manager Don Garcia.
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In synchronization with the Bidwell screed's
leveling roller, workers shovel the wet concrete from high points to low points.
Standing on top of the screed is its operator. The Bidwell was moving lengthwise,
from the 359-foot-long bridge's south end (far right, where the worker is leaning
out with a leveling tool) to its north end.
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Another type of Bidwell, one that workers can
walk across to perform final leveling actions, is being bolted together for use later
in the concreting process.
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A steady procession of cement trucks kept the
pumping machine (far right) busy. Four mixers can be seen in this photo. The
photo looks northwest from the bridge construction area toward Cimarron Street
west of the I-25 interchange. At this time, Sept. 13 at about 5 p.m., Cimarron was
still open to traffic. But later in the evening, when the bridge concrete work -
moving south to north - was nearing the point where it would be above the
roadway, Cimarron was closed to traffic both ways (and remained closed until
Sept. 14 at about 5 a.m.) because of the risk of wet concrete slopping down on
cars. Note: The construction vehicles are parked on previously laid concrete that
will eventually become the new Cimarron Street alignment and the start of the
new southbound on-ramp.
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During the pour, a worker smooths concrete at
the east edge of the new bridge. Just to the east can be seen the northbound and
southbound lanes on the existing Cimarron/I-25 bridge, which will be demolished
this fall to make room for construction of the other lengthwise "half" of the new
bridge.
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