Teamwork makes the dream work at the U.S. Army Engineer Research and Development Center (ERDC). Two ERDC laboratories, the Geotechnical and Structures Laboratory (GSL) and Cold Regions Research Engineering Laboratory (CRREL), collaborated to conduct several full-scale placements of JetCon JC400 rapid-setting concrete as a part of the Office of the Under Secretary of Defense for Research and Engineering’s Foreign Comparative Testing program.
“Working with CRREL was great,” said Will Carruth, a research civil engineer with GSL. “They possessed the technical knowledge and experience needed to properly investigate placing rapid-setting concrete in cold temperatures as well as the required facilities.”
The collaborative effort was conducted in CRREL’s Frost Effects Research Facility where ambient temperatures were held at approximately 25ºF. Placements were heavily instrumented with temperature sensors at locations and depths within the test slab. Core samples were extracted for strength testing, and overall stiffness was evaluated with a heavy weight deflectometer.
“The testing is expected to be incorporated into tactics, techniques and procedures — or TTPs — for using JetCon JC400 in subfreezing temperatures,” said Carruth. “Use of an accelerator — aluminum sulfate — was shown to be effective at mitigating the effects of the cold temperatures, which otherwise would have slowed the set time.”
Researchers say this type of testing is important as JetCon JC400 is a rapid-setting concrete product manufactured in South Korea and previously performed well under simulated aircraft traffic in temperate climates but had not been evaluated in sub-freezing temperatures. While initial laboratory testing was helpful, laboratory samples lack the thermal mass to allow the hydration process to initiate, which is needed to properly represent the curing conditions of a larger concrete repair.
The temperature data collected will also inform a modeling effort that will give users the ability to predict set time based on the temperatures of the ambient air, mix water, dry materials and the ground surrounding the repair.