Background: Portland cement traditionally used with inert aggregates to form construction concrete is made in a high-temperature process that releases large amounts of carbon dioxide (CO2). With rising energy costs, high temperature processes depress profits, and release of CO2 is undesirable from an environmental perspective. It would be ideal if Portland cement could be replaced in some circumstances with an alternative material that could be made at ambient temperatures and that consumed, rather than released, CO2. This technology provides such an alternative.
Applications:• When a conformable building material, substitutable for Portland cement-based concrete, is needed• Where strong, environmentally benign building materials called for• When high strength/cross section required
Advantages:• Surpasses Portland cement in compressive strength• Carbon dioxide absorbed into the concrete during the curing process, rather than released• Eliminates need for high-temperature firing, reducing energy costs• Consumes coal fly-ash and other high silicate wastes; can be used for long-term sequestration of toxic waste material
The Technology: This iron-based cement hardens through a benign chemical equivalent of corrosion. Under proper conditions, the energy released can be used to form strong bonds between sand grains and other aggregates. In Portland cement and other hydraulic cements, bonds between growing crystals are formed by hydration. In this new cement, crystals grow by reacting with carbon dioxide to form iron carbonates, so carbon dioxide becomes an integral, permanent part of the crystalline matrix. The result is a pioneering example of a new class of carbonate cements. Traditional concrete includes silicate materials like sand and gravel. Recently, finer forms of silica like fly ash (waste from coal-burning power plants) have been substituted, and can increase the density and strength of concrete. The new iron cement takes this approach further, using much more fly ash and creating stronger bonds between the silica particles, thus yielding a material with a compressive strength higher than that of Portland cement. Unlike the production of Portland cement, which consumes enormous energy and releases large amounts of environmentally undesirable CO2, this new cement is produced in a process that consumes CO2 and takes place at ambient temperatures.
Stage of Development: Tested on laboratory scale
Lead Inventor: David A. Stone, Ph.D.
Status: US, EP and Canadian patent applications filed.
Refer to Case No. UA06-001