A selective hydration treatment to enhance the utilization of CFBC ash in concrete
- Centre d`Etudes et de Recherches du Charbon, Mazingarbe (France). Groupe Charbonnages de France
- CANMET, Ottawa, Ontario (Canada). Energy Research Labs.
Circulating FBC ash does not normally conform either to North American or European standards as a component or additive to concrete. This is because sulfur capture produces SO{sub 3} contents which are too high, and SiO{sub 2}, Al{sub 2}O{sub 3} contents which are too low. Moreover, the available free lime content can cause structural damage in concrete despite CFBC cementitious properties. A new selective treatment has been developed which allows quantitative conversion of free lime content to Portlandite. This hydration treatment is selective and doesn`t affect the hydraulic or pozzolanic potential of CFBC ash. A new method now also exists to determine the residual CaO content in presence of Ca(OH){sub 2}, which provides the possibility of rapid and cheap quality control for the treated ashes. This hydration treatment can significantly enhance CFBC ash utilization in many areas: concrete, road subbase, or use in embankments and also backfill applications or landfill disposal. In addition, the method offers additional benefits in terms of reduced water demand, reduction in heat release from ash on placement in a landfill or use in cementitious applications. It also causes significant reduction in the swelling behavior and hence dimensional instability in hardened pastes, for cementitious applications, which otherwise result from delayed hydration or unreacted CaO in the CFBC residues. Results are presented from standardized tests, applied to CFBC ash use in concrete, which demonstrate the considerable advantages of the new hydration process for utilization of CFBC ash in concrete.
- OSTI ID:
- 287974
- Report Number(s):
- CONF-950522--; ISBN 0-7918-1305-3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM OXIDES
ASHES
BACKFILLING
CALCIUM HYDROXIDES
CALCIUM OXIDES
COMPRESSION STRENGTH
CONCRETES
CURING
EXPANSION
EXPERIMENTAL DATA
FLUIDIZED-BED COMBUSTORS
FOUNDATIONS
GROUND DISPOSAL
HYDRATION
ROADS
SILICON OXIDES
SORBENT INJECTION PROCESSES
SULFUR TRIOXIDE
SWELLING
WASTE PRODUCT UTILIZATION