A team from Purdue University has developed a new type of cement that cures in below-freezing temperatures, an innovation which is expected to save vast amounts of money that are spent heating construction sites.
The team is led by Charles J Korhonen, a research civil engineer with the U.S. Army Engineer Research and Development Center’s Cold Regions Research and Engineering Laboratory in Hanover, N.H.
Korhonen has received a national award for developing the cement to solve a problem at the Sequoyah Nuclear Power Plant, operated by the Tennessee Valley Authority and located near Chattanooga, Tenn.
The concrete floors in the plant’s ice-storage rooms had heaved upward because of frost action and needed to be repaired. The dilemma was that the work had to be done under the tight time constraints of a nuclear refueling outage and at minus 8 degrees Celsius, the operating temperature of the ice-storage rooms. The storage room temperature was too cold for ordinary concrete to cure properly. Shutdown of the rooms was not possible, since each day of shutting down the plant represented $1 million in lost revenue and service interruptions to utility customers.
Korhonen, in a joint effort with the Tennessee Valley Authority, S&ME Singleton Labs in Louisville, Tenn., and a private material and concrete construction consultant, developed a lightweight Portland cement mixture that allowed repairs without shutting down the nuclear plant or disrupting service.
‘This technology for placing concrete at sub-freezing temperatures could extend the concrete construction season by several months in much of North America,’ said Korhonen. ‘Currently, the U.S. construction industry spends about $1 billion dollars per year to provide heated enclosures for placing concrete at below-freezing outdoor temperatures. Approximately $800 million of that cost is in heat from non-renewable fossil fuels, much of which could be saved by adopting this new low-temperature concrete technology.’
Current construction techniques for using concrete in cold weather have remained largely unchanged since the 1950s, said Menashi Cohen, a professor of civil engineering at Purdue and Korhonen’s advisor. The ingredients in concrete have to be heated to melt any ice, and the concrete must be kept warm until it gains sufficient strength. Korhonen’s work shows that concrete can gain strength at below-freezing temperatures without the need for heat, he said.
As part of his doctoral thesis, Korhonen is investigating how durable low-temperature concrete mixtures are in terms of how well they stand up to the constant freezing and thawing of everyday use. This question is important because the freeze-thaw cycle is a major cause of damage in concrete structures.