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Fly Ash As A Binder in Aggregate Base Courses

Published online by Cambridge University Press:  21 February 2011

Petros Zenieris  and
Joakim G. Laguros
Petros Zenieris
Affiliation:
Standard Testing and Engineering Co., Oklahoma City, Oklahoma 73105
Joakim G. Laguros
Affiliation:
School of Civil Engineering and Environmental Science, The University of Oklahoma, Norman, Oklahoma 73019 USA
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Abstract

The benefit of adding up to 35 wt% Class C high calcium fly ash to various types of fine and coarse aggregate pavement mixes is described and quantified. The mixes, which were compacted to maximum dry density at optimum moisture content, had variable compressive strengths during the first 28 days of curing; after that they assumed a relatively uniform pattern of strength gain reaching values as high as 11 MPa (1600 psi). Mixes containing 15% fly ash gave unacceptably low strengths. XRD measurements indicated massive formation of ettringite, transforming to monosulfoaluminate and the poorly crystallized hydrated phases of C-A-H, C-A-S-H and C-S-H. This transformation helps explain the gain in strength of the mixes with extended curing. SEM observations depicted progressive packing and densification of the skeletal matrix as the hexagonal phases and C-S-H gained higher crystallinity and formed aggregated masses. Furthermore, these observations suggest that fly ash acts predominantly as a chemical binder and partly as a filler in the aggregate mixes tested.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 113: Symposium Q – Fly Ash and Coal Conversion By-Products IV , 1987 , 231
Copyright
Copyright © Materials Research Society 1988

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References

REFERENCES

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