Influence of Residual Carbon in Fly Ash on Microstructure and Strength Development of Mortars and Concretes

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Title: Influence of Residual Carbon in Fly Ash on Microstructure and Strength Development of Mortars and Concretes

Author(s): H. Hornain, F. L. Miersman, and J. Marchand

Publication: Special Publication

Volume: 132

Issue:

Appears on pages(s): 21-36

Keywords: carbon; compressive strength; flexural strength; fly ash; microstructure; porosity; scanning electron microscope; strength; Materials Research

Date: 5/1/1992

Abstract:
Effect of residual carbon content in fly ash on the hardened cement paste properties was investigated. Mortars and concretes were prepared with three different aluminosilicate-type fly ashes of the same mineralogical composition but containing, respectively, 5, 7, and 12 percent of residual carbon. Mixtures containing 15 and 30 percent of fly ash, as replacement of cement, were studied. The microstructure was studied by means of SEM observations and EDS analysis. Pore-size distributions were determined by mercury intrusion porosimetry. Compressive and flexural strengths were measured after 2, 7, 28, and 90 days. Results indicate that the residual carbon content in fly ash does not have any detrimental influence on the microstructure and on the mechanical strength development even at the highest carbon content.