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Green is the New Gray
When 725 Ponce opens in 2019, the new 15-level high rise will be the largest structure ever built with CarbonCure.
Eco-friendly concrete measures help construct 725 Ponce high rise in Atlanta
STURTEVANT, WISCONSIN (October 29, 2018) – A new mixed-use development in one of Atlanta's trendiest neighborhoods – 725 Ponce – is a real-life example of the impact of building a high rise with eco-friendly concrete measures. Atlanta-based companies Thomas Concrete supplied a “green” carbon neutral concrete, and Pioneer Concrete Pumping pumped it using a strategic selection of Putzmeister concrete placing system, which also offered environmental benefits.
Concrete is the most abundant man-made material on earth. However, it has an emissions problem. The process of making cement, its essential ingredient, requires superheating calcium carbonate, or limestone, which releases carbon dioxide (CO2) into the atmosphere. As a result, cement is responsible for up to seven percent of global man-made greenhouse emissions. However, new technology creates concrete that traps CO2 emissions forever.
A few companies provide variations of this technology. The type used for 725 Ponce is CarbonCure™, which ready mixed supplier Thomas Concrete has been using since 2016. The propriety system takes captured and recycled CO2 and injects it into concrete as it's being mixed. Once the concrete hardens, the carbon is sequestered forever. The gas will never be re-emitted into the air because it's been chemically converted into a solid calcium carbonate mineral embedded in the concrete. Plus, the mineral itself improves the compressive strength of the concrete. However, the same compressive strength of traditional concrete can be achieved by simply using less cement.
To create the green concrete, Thomas pays a fee to use CarbonCure's signature system and then buys captured CO2 from a fertilizer plant where it's emitted, but the company says those costs can even out with what they save by using less cement. On 725 Ponce, it was between five to 12 percent less cement depending on the specific mix, which ranged from 3,000 to 8,000 psi.
“After discussions with the project’s owner to the structural engineer, everyone was on board to pump this project with CarbonCure technology, and everything went off like clockwork, from the mix design to pumping it without any issues,” said Justin Lazenby, Manager of Technical Services at Thomas Concrete. An external test lab monitored the results.
When 725 Ponce opens in 2019, the new 15-level high rise will be the largest structure ever built with CarbonCure. The mix was incorporated into the three-level underground parking structure and 12-story 360,000-square-foot (33,445m²) Class A office building that will include a 60,000-square-foot (5,574m²) Kroger grocery store on the first floor.
Looks the Same
Brasfield and Gorri is the general contractor. They, in turn, selected Pioneer to pump the concrete, as they have relied upon the pumping company's services for numerous projects over the years. Pioneer offers 40 years of experience in the concrete industry, provides ACPA-certified operators and features an expansive fleet of truck-mounted boom pumps, trailer-mounted pumps, truck-mounted line pumps (City PumpsTM), and separate placing booms – with almost every size available.
"Our Putzmeister pumps can handle the harshest mixes, so we're prepared to pump tough mixes when our equipment shows up at a pour. However, the concrete dispatched to this job didn't look any different than traditional concrete, and we had no issues pumping it," says Dan Inglese, Pioneer's National Sales Manager for the Atlanta and Dallas markets.
When starting the project, various sizes of truck-mounted boom pumps handled concrete placement on the lower levels. Jobsite congestion meant equipment setup was challenging. When required to position a boom pump in tight spots, Putzmeister’s exclusive one-sided support (OSS) outrigger system on the boom pumps allowed the operator to reduce the outriggers on the non-working side of the unit. This feature removes the option for operators to 'short-rig' machines without the proper safety systems employed.
When the climb up the high rise began, two Putzmeister MX 36/40Z separate placing booms were selected for their maximum horizontal reach of 115' 2" (35.10m). They were attached to two RS 750 pin towers. To get a jump start on the project, a 50-foot (15.24m) tower and two 10-foot (3.05m) tower sections were combined to attain a 70-foot (21.34m) height. The tower was bolted to the slab using four corner plates.
"This approach offered the ability to start placing concrete sooner on the project," says Lee Bentley, a project sales rep for Pioneer with more than 35 years of experience in the concrete pumping industry. The setup allowed for concrete placement on the first deck while avoiding dragging hose over the post tension cables. The 70-foot (21.34m) tower was used for the first four levels, at which point, the crane then lifted and removed the two 10-foot (3.05m) sections.
"The process of removing the tower sections was so easy – just pop out four pins and lift,” said Bentley. Once the sections were removed, the tower was converted to a standard 50-foot (15.24m) self-jacking tower, the same as the other tower on the project.
When pumping the concrete, scaffolding in the basement was in the way so crews turned to a 40Z-meter truck-mounted boom pump to set up on the congested site and extend its boom to reach an open section on the podium level. At this point, the boom hooked into five-inch (125mm) delivery line, which travelled 80 foot (24.38m) to one placing boom tower, and 120 foot (36.58m) to the other tower in the opposite direction. A 90-degree elbow was used to switch the delivery line from one direction to the other.
When the scaffolding was removed, a City Pump line pump was positioned inside the building on the lower parking deck to pump the concrete. "The line pump never missed a beat," says Inglese. "The contractor wanted 80 cubic yards an hour (60m³/hr) and the machine easily delivered." The line pump is capable of a maximum output of 139 yd³/hr (106m³/hr) and maximum pressure of 2,176 psi (150 bar) – on the rod side.
The City Pump CP 2100 HP-D model is a recent addition to Pioneer's fleet and has a Kenworth T880 chassis with a Tier 4 diesel engine designed to reduce emissions. The vehicle used a Diesel Exhaust Fluid (DEF), which was sprayed into the exhaust stream of the diesel vehicle to break down dangerous Nitrogen Oxides (NOx) emissions into harmless nitrogen and water.
"Using this model made a really big difference,” said Bentley. "It was extremely quiet; and although the contractor vented the exhaust stack, it wasn’t necessary because the diesel burned cleaner. Exhaust did not come out like big black bursts of smoke that would spot the structure above and require extensive power washing and cleanup afterwards.”
The overall placing system setup helped accomplish three pours per floor to finish a floor a week, handling 400 cubic yards (305m³) per pour. Meanwhile, the crew worked five days a week to keep the process moving on a fast track.
Construction of the $200 million building consumed 48,000 total cubic yards (36,700m³) of concrete made with CarbonCure. Ultimately, 725 Ponce will save 1.5 million pounds (680 metric tons) in CO2 from being released into the air – the same amount 800 acres of forest would need to sequester (or absorb) in a year to help reduce greenhouse gas emissions.
Lazenby notes, “We feel this technology will become more common,” and CarbonCure claims that by realizing the full potential of their portfolio of technologies, up to 700 megatons of CO2 emissions could be saved annually, which is the same as taking 150 million cars off the road every year.
Also assisting in the green initiative, Tier 4 compliant engines, as found on today’s newer concrete pumps, are also significantly reducing emissions. Consequently, 725 Ponce is a step in an environmentally conscious direction, and more of that gray concrete and the equipment placing it are showing major signs of going green.
Architect: Cooper Carry, Inc. —Atlanta, Georgia
General Contractor: Brasfield & Gorrie—Kennesaw, Georgia
Concrete Supplier: Thomas Concrete—Buckhead, Georgia
Concrete Placing Company Pioneer Concrete Pumping—Smyrna, Georgia (Atlanta) headquarters with locations in Dallas, San Antonio and Nashville
Equipment: Putzmeister MX 36/40Z separate placing booms (2), Putzmeister RS 750 pin towers (2) with floor plate set, City PumpTM CP 2110 HP-D truck-mounted line pump, and various truck-mounted boom pump models
725 Ponce is a real-life example of the impact of building with eco-friendly concrete measures.
As scaffolding in the basement was in the way, a 40Z-meter boom pump was used to pump concrete to each placing boom tower, extending its boom to hook into five-inch (125mm) delivery line that traveled distances up to 120 feet (36.58m).
A 70-foot (21.34m) tall Putzmeister placing boom tower, bolted tot the slab with a floor plate set, allowed crews to start placing concrete sooner.
The high pressure and high input of the City PumpTM line pump was used for pumping concrete for the upper levels of 725 Ponce.