In cold temperatures, fresh concrete can be irreversibly damaged by internal freezing before adequate strength has developed, and the rate at which strength develops is slowed. Industry-standard cold weather protection measures are frequently laborious, expensive and time-consuming. In cold regions, more conservative approaches involving active heating are often the default choice, resulting in considerable added cost.
U.S. Army Engineer Research and Development Center (ERDC) researchers have developed Additive Regulated Concrete for Thermally Extreme Conditions – or ARCTEC – to enable the use of commonly available concrete additives as alternative freeze-protection in cold conditions. ARCTEC builds upon pioneering work performed at ERDC over the last several decades, with the goal of improving the user-friendliness, economy and utility of the technology.
Dr. Ben Watts and Danielle Kennedy, both research civil engineers at the ERDC Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, New Hampshire, have been refining and expanding ARCTEC applications.
“ARCTEC addresses the problem of protecting concrete from freezing during winter construction, which normally requires energy, labor and resource-intensive measures such as heated enclosures,” Watts said. “These methods slow the pace of construction, create additional CO2 emissions, and fail to fully leverage the heat released by concrete naturally.”
A core component of ARCTEC is guidance to recommend the required dosage of additives for a successful concrete placement. This recommendation depends upon multiple aspects of a placement, including geometry, mixture proportions, ambient temperature, wind and time of placement.
The number of unique cases required for general guidance precludes physical testing of every possibility, so a temperature rise model was created to simulate the effects of placement characteristics on the evolving thermal behavior of concrete placed at a range of additive dosages. Inputs for this model were obtained through laboratory characterization of the thermal and mechanical behavior of concrete at multiple curing temperatures and additive dosages.
When combined with synthetic daily temperature profiles, variable convective boundary conditions, a range of placement geometries and constructions, and maturity-informed success criteria, these inputs result in the ability to define the optimal additive dosage over a broad range of possible placement configurations.
“ERDC developed ARCTEC through collaborations with USACE Great Lakes and Ohio River Division, Pittsburgh District, and the Maine Army National Guard, to provide a process to quantify and regulate the natural heat release of curing concrete, combined with a methodology to evaluate the effects of changing heat release on the behavior of concrete placements in cold environments,” Kennedy said.
“The ARCTEC methodology accounts for differences in placement size and shape, mixture design and ambient temperature and provides the user with an additive dosage recommendation to protect from freezing in those conditions.”
Another benefit to using ARTEC is that it can be used in any application where concrete construction in cold weather is required.
“In the near future, ARCTEC research is focused on the refinement of generic guidance for end users; publication of simple, standardized testing procedures for heat-release measurement; and the incorporation of ARCTEC methods into industry-standard cold-weather concrete guidance,” Watts said.
ARCTEC is also being evaluated in the context of military engineering for use in extreme cold applications. Within this research area, future efforts will focus on developing novel additives and extreme cold placement techniques.
During a visit to CRREL in New Hampshire, Dr. Steven Wax, acting Assistant Secretary of Defense for Science and Technology in the Office of the Under Secretary of Defense for Research and Engineering said, “Material performance in the cold is different, and we must understand this to adapt to support current operations.”
As one of the world’s premier centers for cold regions research, CRREL is uniquely positioned to meet the challenges encountered in some of Earth’s harshest and most austere cold environments.
“ARCTEC is a tool which enables cost and schedule savings for construction and repair of civil and military infrastructure,” Watts said. “Decades of research and collaborative partnerships went into development of ARCTEC, which we believe will be a game changer for construction in cold weather.”