Next generation enhancement of cements by the addition of industrial wastes and subsequent treatment with supercritical CO{sub 2}
- Los Alamos National Lab., NM (United States)
- Materials Technology Ltd., Reno, NV (United States)
- Univ. of Nevada, Reno, NV (United States). Chemical Physics Program
The natural curing reactions which occur in a standard portland cement involve the formation of portlandite, Ca(OH){sub 2}, and calcium silicate hydrates, CSH. Over time, the cured cement abstracts carbon dioxide, CO{sub 2}, from the air, converting the portlandite and CSH to calcium carbonate, CaCO{sub 3}. It turns out, however, that this secondary conversion results in the blockage and/or closure of pores, drastically slowing the reaction rate with time. By exposing a portland cement to supercritical CO{sub 2} (SCCO{sub 2}), it is found that the carbonation reaction can be greatly accelerated. This acceleration is due to (1) the ability of the supercritical fluid to penetrate into the pores of the cement, providing continuous availability of fresh reactant, in hyper-stoichiometric concentrations; and (2) the solubility of the reaction product in the supercritical fluid, facilitating its removal. By accelerating the natural aging reactions, a chemically stable product is formed having reduced porosity, permeability and pH, while at the same time significantly enhancing the mechanical strength. The supercritical CO{sub 2} treatment process also removes a majority of the hydrogenous material from the cement, and sequesters large amounts of carbon dioxide, permanently removing it from the environment. The authors describe the general features of supercritical fluids, as well as the application of these fluids to the treatment of cements containing industrial waste. Some of the issues concerning the economic feasibility of industrial scale-up will be addressed. Finally, some initial results of physical property measurements made on portland cements before and after supercritical fluid CO{sub 2} treatment will be presented.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Human Resources and Administration, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 541797
- Report Number(s):
- LA-UR-97-2104; CONF-9706177-; ON: DE97008975; TRN: AHC29723%%14
- Resource Relation:
- Conference: 1997 green chemistry and engineering conference: implementing vision 2020 for the environment, Washington, DC (United States), 23-25 Jun 1997; Other Information: PBD: [1997]
- Country of Publication:
- United States
- Language:
- English
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