Available alkalis in fly ash and their effects on alkali-aggregate reaction

Thesis/Dissertation · Wed Jan 01 00:00:00 EST 1986

OSTI ID:6446640

Lee, C

The available alkalis of four Class C and two Class F fly ashes were evaluated according to ASTM C 311. The effects of alkalis in three Class C fly ashes on expansion of mortar bars with high and low-alkali cements were studied using the procedures described in ASTM C 441. This research studied: (1) the significance of the standard available alkali test for analyzing different fly ashes, (2) the possibility of reducing the time required to complete the test, (3) the significance of the standard mortar bar test in determining the degree to which high and low-alkali cements could be replaced by Class C fly ashes, (4) effect of fly ash alkali contents on alkali reactivity, and (5) the ability of Class C fly ash to improve concrete's resistance to external alkali attack. The results indicated that the ASTM C 311 tends to underestimate the ultimate available alkali content in Class C fly ash. An empirical equation was developed to estimate the ultimate concentration of available alkalis in fly ash or of active alkalis in cement fly ash paste from the known total equivalent Na2O/SiO2 (N/S) mole ratio. The results also indicated that replacements of small amounts of high-alkali cement with Class C fly ash resulted in increased expansion as compared to plain cement mortars. Replacements of low-alkali cement with Class C fly ash up to 40% also increased expansion. A critical N/S mole ratio was identified and found to characterize alkali reactivity. The replacement of the cement with fly ash was found to provide a degree of protection from external alkali attack. Expansions caused by external alkali attack were found to be inversely related to N/S mole ratio of the cementitious materials.

• Research Organization: Iowa State Univ. of Science and Technology, Ames (USA)
• OSTI ID: 6446640
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
CONCRETES
WASTE PRODUCT UTILIZATION
FLY ASH
CHEMICAL ANALYSIS
HYDROXIDES
AVAILABILITY
CEMENTS
COMPARATIVE EVALUATIONS
CORROSION RESISTANCE
CURING
EQUATIONS
EXPANSION
MEASURING METHODS
MORTARS
SILICON OXIDES
SODIUM OXIDES
TIME DEPENDENCE
AEROSOL WASTES
ALKALI METAL COMPOUNDS
ASHES
BUILDING MATERIALS
CHALCOGENIDES
HYDROGEN COMPOUNDS
MATERIALS
OXIDES
OXYGEN COMPOUNDS
RESIDUES
SILICON COMPOUNDS
SODIUM COMPOUNDS
WASTES
010800* - Coal
Lignite
& Peat- Waste Management
010600 - Coal
Lignite
& Peat- Properties & Composition