Composition effects on durability of aggregates made from coal combustion by-products
- CONSOL Inc., Library, PA (United States)
High-strength aggregates were made by pelletizing coal combustion by-products from the fluidized-bed combustion (FBC) and spray dryer absorption (SDA) FGD processes. The aggregates made from the FBC by-product meet the American Association of State Highway and Transportation Officials (AASHTO) soundness index and other specifications for Grade A course aggregate used as the surface-wearing course in road construction. However, the aggregates degraded when they were fully immersed in water during long-term natural weathering and laboratory freeze/thaw tests. Characterization of the degraded aggregates indicates that the slow hydration of anhydrite (CaSO{sub 4}) to gypsum (CaSO{sub 4}{center_dot}2H{sub 2}O) is the major cause for the degradation. Aggregate durability was improved by blending the FBC by-product with fly ash and by coating with asphalt. Aggregate durability is being tested under heavy truck traffic in a flexible bituminous asphalt test patch in which FBC by-product aggregate constitutes 50% of the coarse aggregate. In contrast to FBC by-product, most of the spent sorbent in spray dryer FGD by-product is in the form of calcium sulfite, rather than calcium sulfate anhydrite. Synthetic aggregates made with spray dryer by-product and no additive have good durability in both long-term weathering and laboratory freeze/thaw tests.
- OSTI ID:
- 257017
- Report Number(s):
- CONF-950952-; TRN: IM9631%%223
- Resource Relation:
- Conference: 12. annual international Pittsburgh coal conference, Pittsburgh, PA (United States), 11-15 Sep 1995; Other Information: PBD: 1995; Related Information: Is Part Of Twelfth annual international Pittsburgh coal conference: Proceedings. Coal -- Energy and the environment; Chiang, S.H. [ed.]; PB: 1248 p.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
ASHES
WASTE PRODUCT UTILIZATION
SLUDGES
GRANULAR MATERIALS
MECHANICAL PROPERTIES
PAVEMENTS
CALCIUM SULFATES
HYDRATION
FLY ASH
ADDITIVES
PROTECTIVE COATINGS
FREEZING
THAWING
BITUMINOUS COAL
COMBUSTION
CHEMICAL COMPOSITION
ABRASION
COMPRESSION STRENGTH
DENSITY
PARTICLE SIZE
EXPERIMENTAL DATA