A mixture of fly ashes as road base construction material
Journal Article
·
· Waste Management
- TNO Environmental and Energy Research, Apeldoorn (Netherlands). Dept. of Environmental Technology
By order of NOVEM, a research was carried out by TNO Environmental and Energy Research into the formation, occurrence and disintegration of ettringite in stabilizations of a mixture of fluidized bed fly ash and powder coal fly ash. Two series of specimens were manufactured, one from fluidized bed fly ash only and one from a mixture of fluidized bed fly ash and powder coal fly ash. From both series of specimens the compressive strength and the formation of minerals were determined at different times between 2 and 890 days after manufacture. The quantity of ettringite present in the specimens and the compressive strength both show a maximum. During the first couple of weeks calcium hydroxide, calcium sulfate and aluminum hydroxide are transferred into ettringite. The formed ettringite fills the pores and thus contributes to the strength development. However, if too much ettringite is formed, the specimens explode due to expansion. In the course of time (100--200 days after manufacture) the formed ettringite again disintegrates, as a consequence of carbon dioxide attack. Then the compressive strength decreases, but stabilizes at a lower level. If the content of calcium oxide in the mixture of raw materials is not beyond 12%, and the mixture is allowed to react before manufacture of the specimens, the formed ettringite does not cause any crack formation in the specimens. It is possible to construct good and cheap stabilizations from a mixture of fluidized bed fly ash, powder coal fly ash and sand, without the addition of binding agents.
- OSTI ID:
- 464816
- Report Number(s):
- CONF-9509276--
- Journal Information:
- Waste Management, Journal Name: Waste Management Journal Issue: 1-3 Vol. 16; ISSN WAMAE2; ISSN 0956-053X
- Country of Publication:
- United States
- Language:
- English
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