Abstract
The microstructure of air voids in both air-entrained and non air-entrained paste, mortar, and concrete has been studied at different ages (5 min to 60 days) in order to understand how air-entrained voids form in portland-cement systems. Scanning electron micrographs of air voids are presented for different ages. The solidification process of portland-cement paste and mortar was frozen at different ages using a low temperature scanning electron microscope and freeze drying. At very early ages the air voids show thin shells made of very fine particles. The packing of the cement grains behind the air void varies, depending on the water-to-cement ratio. Air voids appear to have the same interface with the cement paste matrix as aggregates. No readily visible difference was found between entrapped and entrained air voids.
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References
F. H. Jackson, J. Am. Concrete Institute 15 (6), 509–569 (1944).
W. L. Dolch, in Concrete Admixtures Handbook, Properties, Science, and Technology, edited by S. Ramachandran, 1984, pp. 269–302.
F. H. Jackson and A. G. Timms, Public Roads 27, 259 (1954).
R. C. Mielenz, V. E. Wolkodoff, J. E. Backstrom, and H. L. Flack, J. Am. Concrete Institute, American Concrete Institute 30 (1), 95–122 (1958).
P. J. M. Monteiro, S. J. Bastacky, and T. L. Hayes, Cement and Concrete Res. 15, 687–693 (1985).
B. J. Dalgleish and P. L. Pratt, J. Mater. Sci. 17, 2199–2207 (1982)
P. Echlin, R. Paden, and R. Wart, Proc. 3rd Annual Scanning Electron Microscopy Symp., IIT Research Institute, Chicago, IL, 1970, p. 51.
P. Echlin, J. Microsc. 112, 47 (1977).
A.I. Rashed, P. J. M. Monteiro, R. B. Williamson, and J. astacky, ASTM Cement, Concrete & Aggregate 11 (2), 126–128 (1989).
P. K. Mehta, Concrete Structure, Properties, and Materials (Prentice-Hall, Englewood Cliffs, NJ, 1986).
H. J. Jennings, B. J. Dalgleish, and P. L. Pratt, J. Am. Ceram. Soc. 64, 567–572 (1981).
H. J. Jennings, “The Developing Microstructure in Portland Cement,” in Advances in Cement Technology (Pergamon Press, 1983).
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Rashed, A.I., Williamson, R.B. Microstructure of entrained air voids in concrete, Part I. Journal of Materials Research 6, 2004–2012 (1991). https://doi.org/10.1557/JMR.1991.2004
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DOI: https://doi.org/10.1557/JMR.1991.2004