Chloride Extraction

Nova Award

The NOVA Award, which has been referred to as the "Nobel Prize" for construction was awarded to the Norcure system in 1996. It is awarded annually to noteworthy innovative solutions, processes or products that improve the quality, efficiency and cost effectiveness of construction.

The Norcure system was nominated by David Whitmore of Vector Construction, Fargo, ND.

The Norcure system is a rehabilitation method developed to remove salt (chloride ions) from salt contaminated concrete structures. The removal of chloride ions stops the corrosion of embedded reinforcing steel and greatly extends the service life of salt contaminated structures.

Conventional methods to deal with chloride contaminated concrete require the removal of the contaminated concrete and replacement with uncontaminated concrete. These conventional methods are noisy, dirty, time consuming, costly, and some cases, structurally detrimental.

In the Norcure system, chloride ions are drawn out of the concrete by applying a low voltage, direct current electric field between a temporary anode on the surface of the structure and the reinforcing steel within the concrete. Chloride ions migrate from areas near the reinforcing steel toward the anode and out of the concrete. At the same time as chlorides are being removed, hydroxyl ions are produced at the surface of the rebar within the structure. The production of hydroxyl ions restores the alkalinity of the concrete. This feature of the Norcure system allows it to be used to re-alkalize carbonated concrete.

The Norcure process is a quiet, clean and nondestructive method. The process takes about six to ten weeks to reduce the chloride ions in the vicinity of the reinforcing steel to levels required to prevent rusting. Experimental work is underway where lithium-based electrolytes are being tested for their ability to mitigate damage caused by alkali-silica reactive aggregate in concrete.

The idea of electrochemical treatment started in the 1970s. Battelle Institute in Columbus, Ohio, worked together with Kansas DOT using very high voltage in a short time. This heated the concrete and cause some undesirable physical changes, and the efforts were abandoned. About 1988, a Norwegian company, now known as Norwegian Concrete Technologies (NCT), and their lead research engineer, John Miller, began further work in this area. They determined the causes of the previously unacceptable side effects and developed criteria and equipment to eliminate them.

Trial demonstration projects using the Norcure system began in 1989. The first trial project in North America was for the Ontario Ministry of Transportation on a portion of the substructure of the Burlington Skyway. This project was completed as part of the Strategic Highway Research Program (SHRP) which is a jointly funded program of the U.S. and Canada. The first full-scale commercial project in North America was completed n 1994 on a bridge substructure for Saskatchewan Highways and Transportation. The project included the treatment of 24 salt contaminated columns.

There are desalination projects in Norway, Sweden, England, Germany, U.S.A., Canada, Japan, Switzerland and Italy. Altogether, about 50 chloride removal projects have been installed, including those in the U.S.A. Acceptance of the system seems to be growing rapidly now that the long-term results of the early SHRP test projects are available. The Federal Highway Administration is actively trying to promote the use of this technology to state DOT's. Approximately 1,500.000 sq. ft. of concrete has been treated to date.

Other 1996 winners of the NOVA award include a new bolt for use with structural steel, a system for recycling concrete in highway construction, a unique labor bargaining agreement, and a 11,400 sq. ft. pier made out of recycled plastic.

More than 600 construction industry representatives from throughout the United States attended the Annual Innovation Celebration Banquet held March 14 at the Laurel Manor in Livonia, Michigan.

The Construction Innovation Forum is an international, non-profit organization established in 1987. Roger Lane of the Detroit Edison Company is the organization's chair. The Forum is located in Ann Arbor, Michigan at 1000 Campus Drive, Suite 100, Ann Arbor, Michigan 48104-6792. Telephone 313-995-1855; fax 313-995-5002; e-mail: cif@pwb.com