Pore structures of fly ashes activated by Ca(OH)[sub 2] and CaSO[sub 4] [center dot] 2H[sub 2]O

Journal Article · Wed Feb 01 00:00:00 EST 1995 · Cement and Concrete Research; (United States)

DOI:https://doi.org/10.1016/0008-8846(95)00027-5· OSTI ID:6476324

Ma, W; Liu, C; Brown, P W; Komarneni, S ^[1]

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1. Pennsylvania State Univ., University Park, PA (United States)

The nature of the pore structure which develops when low-lime fly ash reacts with Ca(OH)[sub 2] and CaSO[sub 4] [center dot] 2H[sub 2]O under hydrothermal treatment has been investigated. The nitrogen adsorption-desorption isotherms of hydrothermally treated samples of fly ash and activated fly ash were analyzed. X-ray diffractometry was used to characterize the hydration products and SEM was used to analyze microstructure. The shapes and sizes of the hysteresis loops of isotherms and the pore size distribution data indicated that the pore structures of samples were comprised primarily of wedge-shaped pores with open ends. The surface area obtained when fly ash reacted with Ca(OH)[sub 2] under hydrothermal treatment at 100 C was 33.4 m[sup 2]/g, while that of untreated fly ash was only 1.3 m[sup 2]/g. The surface area of fly ash after reaction with CaSO[sub 4] [center dot] 2H[sub 2]O was 2.9 m[sup 2]/g. For fly ash reacted with Ca(OH)[sub 2], the volumes of the pores with radii of 19[angstrom] increased with increasing temperature of thermal treatment. Depending on the temperature, calcium silicate hydrate, calcite and anhydrite formed. Because the pozzolanic reaction produces calcium silicate hydrate with a very large surface area, it controls the pore structures in which fly ash is activated by Ca(OH)[sub 2]. Therefore, a realistic assessment of the pore structure of activated fly ash is needed to understand those important physical and mechanical properties of concrete.

• DOE Contract Number: FG22-91PC91302
• OSTI ID: 6476324
• Journal Information: Cement and Concrete Research; (United States), Vol. 25:2; ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
36 MATERIALS SCIENCE
CONCRETES
MECHANICAL PROPERTIES
PHYSICAL PROPERTIES
FLY ASH
PORE STRUCTURE
WASTE PRODUCT UTILIZATION
ADSORPTION ISOTHERMS
CALCIUM HYDROXIDES
CALCIUM SULFATES
CHEMICAL ACTIVATION
HYDRATES
AEROSOL WASTES
ALKALINE EARTH METAL COMPOUNDS
ASHES
BUILDING MATERIALS
CALCIUM COMPOUNDS
COMBUSTION PRODUCTS
HYDROGEN COMPOUNDS
HYDROXIDES
ISOTHERMS
MATERIALS
MICROSTRUCTURE
OXYGEN COMPOUNDS
RESIDUES
SULFATES
SULFUR COMPOUNDS
WASTES
010800* - Coal
Lignite
& Peat- Waste Management
360603 - Materials- Properties
360606 - Other Materials- Physical Properties- (1992-)