For construction and concrete pumping professionals confronted with challenges, thinking outside of the box is part of the job description. Innovation must have seemed like the order of the day for McShane Construction on a project to construct a new distribution center in Thief River Falls, Minnesota. Dealing with a massive footprint and battling a winter that was harsh even by Minnesota standards, the company drew upon a range of solutions, including pre-warming ready mixed trucks, heated aggregate, hose pulling gear, geo piers, stacked precast panels and more. And helping make it all happen was a pair of concrete pumps that delivered mud through as much as 575 feet of system to keep the project on track. The fact that they pumped the above grade stories from the upper floors down to the lower should not come as a surprise at all.
With a footprint of more than 1 million square feet, the project in which McShane is involved is unarguably huge. Placing it in northwestern Minnesota, however, makes its size and significance all the more impressive. According to McKinley Geiger, project manager for Rosemont, Illinois-based McShane, because of the size, the job is being done in three separate phases, with each phase representing roughly one-third of the overall building.
“The layout of this structure is interesting, in that there are sections of each floor that do not extend the entire length of the building,” he said. “So, in the first section, there are really only two small mezzanines on the second and fourth floors—everything else is clear to the top to make way for automated racking systems which will be installed later. In the second part of the structure, the third floor exists only on the north half of the building, while the second and fourth floors are on the south half—they never overlap. And then there is a fifth floor which is also just a fraction of the full footprint. That made things interesting as we pumped each floor, doing each section from the top down.”
McShane’s decision to pour the project in that manner is being done to accommodate one very basic principle: gravity. Because each floor consists of metal pan decks, anything that they would pour on an upper floor would put the completed floor below it at risk from dripping from above.
“Instead, when you start top down, if anything falls to the deck below—as long as it is not a large amount of concrete which could mess with the structural integrity of the deck—we can just cover it up with the next pour,” said Geiger. “A bit unconventional, but effective nevertheless.”
DIFFERENT IS THE DIFFERENCE
As one might imagine, the pumping effort at the Thief River Falls site was herculean. To make it all happen, McShane subcontracted to Millennium Concrete (Coralville, Iowa), which supplied the Ductilcrete material and technology used for the slab on grade. For the massive day-to-day pumping effort, they, in turn, hired Parkers Prairie, Minnesota-based Bob’s Concrete Pumping. Facing some daunting lengths for the pours, innovation once again ruled the day, according to Geiger.
“Despite one side of the structure being nearly a quarter mile long, the pumper got the job done with a pair of Schwing pumps—an S 36 X and an S 38 SX—as well as some additional placement equipment,” he said. “We did so many different things on this project in order to deal with challenges, including everything from the structure’s size to the weather, which seemed unrelenting at times.”
GETTING FULL EXTENSION
The pumper made use of an area in the middle of sections two and three, which offered a ground-to-roof opening that allowed them to get the S 38 SX pump in and up. While doing so guaranteed access to each floor, that only solved part of the problem. According to Bob Swenson, owner of Bob’s Concrete Pumping, it was the unique design of that pump which really made the difference.
“This was a challenging project, in that we needed to get at five levels of mezzanine decks with really limited overhead space,” he said. “But that’s exactly why we bought the 38 SX and why it handled about 95 percent of the pumping for us out there. That particular boom offers a hyper extension feature at every section, which meant we were able to sit closer and get in further than any other pump in our fleet would have been able to do.”
He added that some of the farthest reaches were nearly 600 feet in, so even though a lot of system would still be necessary, they benefited from every inch of extra reach the 38 SX got them. “The design of that unit’s boom allowed us to get in much further than a standard roll and fold,” he said. “It proved so successful for us, in fact, that the customer is discussing another 70- to 80,000-yard project with us this coming winter. They were definitely pleased.”
As mentioned, even with the 38-meter boom fully extended, the farthest reaches of the decks made the addition of more than 450 feet of system necessary. To help deal with that, the pumper used a pair of radio-controlled Line Dragons to help get line to where it was needed.
“I have a background in concrete work and I’d never seen that before — it was very effective,” said Geiger. “But the fact that those boom pumps were able to efficiently get mud to areas as much as 575 feet away can’t be overstated.”
KEEP THE FIRES BURNING
Geiger said that they were initially looking for concrete production rates in the 30,000 square-feet-per-day range. However, after getting on site and finding the permafrost still several feet down, they quickly learned that Mother Nature had other plans.
“This past winter was not a great one for pouring concrete,” he said. “Even with our planning, we still missed a lot of days. To try to cope with the cold, if we knew we were going to pour the next day, we would have Davidson (the ready mixed contractor) bring some of his trucks over and park them inside a building that was heated. In that way, the steel in the trucks was kept warmer, so that when they loaded up the concrete, it was going into a better environment than a truck that had been sitting outside all night in 30 below zero weather.”
Obviously, McShane was not alone in dealing with the bitter cold of a northwest Minnesota winter. The local office of Davidson Ready Mix & Construction had prepared for the sub-zero temps by having a wood-fired system in place to keep the aggregate pile warm for the project throughout even the coldest months.
“They did a great job of keeping it usable all winter,” said Geiger. “Because all the gravel pits in the area were frozen solid, we couldn’t even get stone for the job site, so their efforts really helped out.”
The massive, million-plus-square-foot slab-on-grade sits atop a series of spread foundation footings which, because of the heavy, fatty clay content of the area soil, needed better support than could be achieved with a grade beam. Geiger said a rammed aggregate pier system proved the solution for that challenge.
“We used an Iowa company called Foundation Service Corporation that came in and drilled what they call geo piers,” he said. “In areas where footings are designed to go, an excavator with an auger attachment at the end drills a hole—or series of holes—removing the material. (Because it is clay, it does not close in on itself.) Then, sand is placed in each hole and another excavator equipped with a ram attachment hammers downward, compressing the material. This is repeated in roughly one-foot lifts until each hole is completely filled, resulting in a solid pier. Some footers have five geo piers supporting them, some have 20. The bottom line was we now had soil stability where there was none before.”
GAINING SOME PERSPECTIVE
To put the size of the project into better perspective from a concrete pumping point of view, consider this: Bob’s Concrete Pumping pumped concrete to five partial floors of pan decks—no slab, no footers or piers—and still pumped more than 25,000 cubic yards on the job. And in many cases, they ran as much as 450 feet of additional system and still kept production rates up.
“There’s no doubt the pumps have been an integral part of this project,” said Geiger. “Any time you are on a tight schedule, dealing with days lost to weather, and having to innovate to make sure reach is never an issue, it gets challenging. But the pumper came armed with equipment that rose to the occasion, ensuring that each of those issues was addressed. This has been an impressive project so far and everyone involved in it has really risen to the challenge.”
The new distribution facility is slated for a 2020 opening.
This article was originally published in Concrete Pumping magazine with contribution by McShane Construction Project Manager, McKinley Geiger. Click here to view the original article.