Carbonation Behavior of Pure Cement Hydrates under Supercritical Carbon Dioxide Conditions - 12199
- Graduate School of Engineering, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya-shi, Aichi-ken, 464-8603 (Japan)
- EcoTopia Science Institute, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya-shi, Aichi-ken, 464-8603 (Japan)
- CEA, DEN, Marcoule, DTCD/SPDE/L2ED, BP 17171, F-30207 Bagnols-sur-Ceze (France)
- CEA, DEN, Marcoule, DTCD/SPDE/LFSM, BP 17171, F-30207 Bagnols-sur-Ceze (France)
- CEA, DEN, Marcoule, DTCD, BP 17171, F-30207 Bagnols-sur-Ceze (France)
Carbonation of cement-based waste forms using a supercritical carbon dioxide (SCCO{sub 2}) is a developing technology for the waste immobilization of radioactive and non-radioactive wastes. However, the detail carbonation behaviors of cement matrices under the SCCO{sub 2} condition are unknown, since cement matrices forms very complex phases. In this study, in order to clarify the crystal phases, we synthesized pure cement hydrate phases as each single phases; portlandite (Ca(OH){sub 2}), ettringite (Ca{sub 6}Al{sub 2}(SO{sub 4}){sub 3}(OH){sub 12}.26H{sub 2}O), and calcium silicate hydrate (n CaO---m SiO{sub 2} ---x H{sub 2}O), using suspensions containing a stoichiometric mixture of chemical regents, and performed carbonation experiments using an autoclave under supercritical condition for carbon dioxide. The XRD results revealed both the carbonate phases and co-product phases depending on the initial hydrate phases; gypsum for Ettringite, amorphous or crystalline silica for calcium silicate hydroxide. Thermogravimetric analysis was also performed to understand carbonation behaviors quantitatively. According to the experimental results, it was found that the major reaction was formation of calcium carbonate (CaCO{sub 3}) in all cases. However, the behaviors of H{sub 2}O and CO{sub 2} content were quietly different: Portlandite was most reactive for carbonation under SCCO{sub 2} conditions, and the CO{sub 2} content per one molar CaO was ranged from 0.96 ∼ 0.98. In the case of Ettringite, the experiment indicates partial decomposition of ettringite phase during carbonation. Ettringite was comparatively stable even under the SCCO{sub 2} conditions. Therefore, a part of ettringite remained and formed similar phases after the ettringite carbonation. The CO{sub 2} content for ettringite showed almost constant values around 0.86 ∼ 0.87. In the case of calcium silicate hydrate, the carbonation behavior was significantly influenced by the condition of SCCO{sub 2}. The CO{sub 2} content for the calcium silicate hydrate had values that ranged from 0.51 ∼ 1.01. The co-products of the carbonation were gypsum (CaSO{sub 4}) for ettringite, silica gel (SiO{sub x}) and silica (SiO{sub 2}) for calcium silicate hydrate, which also contributed to the densification of the particles. The production of co-products enhanced the change to their morphology after the carbonation. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 22293495
- Report Number(s):
- INIS-US-14-WM-12199; TRN: US14V1150115019
- Resource Relation:
- Conference: WM2012: Waste Management 2012 conference on improving the future in waste management, Phoenix, AZ (United States), 26 Feb - 1 Mar 2012; Other Information: Country of input: France; 6 refs.
- Country of Publication:
- United States
- Language:
- English
Similar Records
X-Ray Diffraction of Slag-Based Sodium Salt Waste Forms - 15513
Next generation enhancement of cements by the addition of industrial wastes and subsequent treatment with supercritical CO{sub 2}
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CALCIUM CARBONATES
CALCIUM HYDROXIDES
CALCIUM OXIDES
CALCIUM SILICATES
CALCIUM SULFATES
CARBON DIOXIDE
CEMENTS
CRYSTALS
DECOMPOSITION
HYDRATES
MIXTURES
NONRADIOACTIVE WASTES
SILICA
SILICON OXIDES
SUSPENSIONS
THERMAL GRAVIMETRIC ANALYSIS
WASTE FORMS
X-RAY DIFFRACTION