Researchers at McGill University are working to develop a CO2 curing process for the precast concrete industry that can utilize CO2 as a reactant to accelerate strength gain, reduce energy consumption, and improve the durability of precast concrete products. Carbon dioxide curing of concrete is considered a CO2 storage process. As gaseous CO2 is converted to thermodynamically stable calcium carbonate, the CO2 becomes embedded in calcium silicate hydrate. Concrete masonry blocks and fiber-cement panels are ideal candidate building products for carbon storage, as they are mass-produced, and require steam curing. In order to make the process economically feasible, self-concentrating absorption technology will be studied to produce low cost CO2 for concrete curing and to capture residual CO2 after the curing process. The compact design of the CO2 chamber and low cost carbon capture technology should result in a net process cost of less than $10 per ton of CO2 stored. The proposed research will examine the possibility of achieving a cost-effective, high-performance concrete manufacturing process through a prototype production using specially designed chambers, called CO2 claves, to replace steam kilns and implement forced-diffusion technology to maximize carbon uptake at minimal process costs.
The Department of Energy’s (DOE) Carbon Storage Program encompasses five Technology Areas: (1) Geologic Storage and Simulation and Risk Assessment (GSRA), (2) Monitoring, Verification, Accounting and Assessment (MVAA), (3) Carbon Dioxide (CO2) Use and Re-Use, (4) Regional Carbon Sequestration Partnerships (RCSP), and (5) Focus Areas for Sequestration Science. The first three Technology Areas comprise the Core Research and Development (R&D), which includes studies ranging from applied laboratory to pilot-scale research focused on developing new technologies and systems for greenhouse gas (GHG) mitigation through carbon storage. This project is part of the Core R&D CO2 Use and Re-use Technology Area and focuses on developing pathways and novel approaches for reducing CO2 emissions in areas where geologic storage may not be an optimal solution. Carbon dioxide use and re-use applications could generate significant benefits through the capture or conversion of CO2 to useful products such as fuels, chemicals, or plastics. Revenue generated from these applications could offset a portion of the CO2 capture cost. The program’s R&D strategy includes adapting and applying existing technologies that can be utilized in the next five years, while concurrently developing innovative and advanced technologies that will be deployed in the decade beyond.
The area of CO2 use and re-use for carbon storage is relatively new and less well-known compared to other storage approaches, such as geologic storage. Many challenges exist for achieving successful CO2 use and re-use, including the development of technologies capable of economically fixing CO2 in stable products for indirect storage. More exploratory technological investigations are needed to discover new applications and reactions. Each CO2 use and re-use technology approach has a specific application, advantages over others, and challenges that are the focus of existing and future research. Technologies being developed will work towards meeting carbon storage programmatic goals; and these technologies may provide coal-based electric power generating facilities and other industrial CO2 emitters additional tools to manage CO2 emissions. The objective of this project is to develop a carbon dioxide curing process for pre-fabricated concrete forms. By utilizing carbon dioxide as a reactant, it will be stored within the concrete form. This process could improve the concrete mechanical properties and reduce energy consumption by eliminating the need for steam curing.
Precast concrete products are considered green building products because of their superior performance, minimal environmental impact, quick manufacturing turnaround, and reduced life cycle costs. Precast concrete can be an even more environmental friendly green building product if CO2 curing is used in place of steam curing. Carbonation curing is a chemical reaction of the cement binder with CO2 rather than water. This method of curing can make precast concrete products stronger, less porous, and more durable. Further, carbonation curing using CO2 could improve production cycle efficiency as compared to steam curing. The technology, if successfully demonstrated, will provide a useful application for CO2 that will reduce CO2 emissions associated with the pre-cast concrete production life cycle.
Additionally, the experience gained from this project will help promote application of the process to other products in the precast concrete industry to enhance CO2 utilization capacity. Although the project is still at laboratory scale, it is a complete study of prototype production and can be implemented by scale-up. This technology contributes to the Carbon Storage Program’s effort to identify and support cost-effective methods for CO2 use and re-use.
The goals of the project are to integrate CO2 into various precast concrete forms that consume less energy, generate minimal CO2, and have high performance. This project will be an interdisciplinary laboratory/engineering simulation process study with the following focus areas:
Design and test CO2 claves for concrete blocks and panels: Design and fabricate reaction chambers that will replace existing concrete production curing processes to help maximize CO2 uptake into the concrete structure at minimal costs.
Conduct concrete manufacturing process experiments with commercial sources of CO2: Concrete blocks and panels will be fabricated for varying specifications using a range of processing parameters to validate the design of the CO2 claves, measure the CO2 uptake, and the economic value of the process implemented during initial laboratory testing. The project target is to store approximately 0.75 pounds of CO2 into each 8-inch concrete block.
Performance evaluation of the carbonated products: Short-term (immediately after curing) and long-term (after 28-day subsequent hydration) performance evaluations will be conducted on carbonated products made using commercially produced and recovered gases. Performance testing parameters will include both physical and mechanical properties. Microstructure analysis will show if a carbonate bonded matrix has been formed. Comparisons will be made with commercial products to determine if the new process can be further optimized.
Production of carbonated products with recovered CO2: Carbon dioxide for use in manufacturing precast concrete products will be produced and captured using self-concentrating absorption technology. Carbon dioxide will be recovered for use from flue gas generated from a power plant or from a cement plant.
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