A second-order polynomial equation was fit-
We recommend that additional studies be
done to evaluate the TDR response from a range
ted to the concrete data as shown in Figure 4. Also
of concretes. The concrete should include low to
shown is a 95% confidence band. This band sug-
high paste contents and small to large aggregates.
gests that we can be confident that 95% of the
time a dielectric constant measured with TDR
will be within this envelope. At best, this band is
LITERATURE CITED
within 1/2% of the curve fitted to the data. The
curve for concrete covers a range of water con-
Ansoult, M., L.W . DeBacker, and M. Declercq
tents from 4 to 11%. However, until studies on
(1984) Statistical relationship between apparent
other concretes are conducted, the following
dielectric constant and water content in porous
equation is considered usable only for the partic-
media. Journal of the Soil Science Society of America,
ular concrete used in this study:
48: 4750.
Fellner-Feldegg, J. (1969) The measurement of di-
ω = 0.0001928K 2 + 1.146K 4.425
(3)
electrics in the time domain. Journal of Physical
where ω is volumetric water content (%), and K is
Chemistry, 73: 616623.
the dielectric constant.
Handbook of Chemistry and Physics (1977) 58th
Edition, Cleveland, Ohio: Chemical Rubber Com-
pany Press.
CONCLUSIONS AND RECOMMENDATIONS
Lange's Handbook of Chemistry (1973) Eleventh
Edition (J.A. Dean, Ed.), New York: McGraw-Hill.
A relationship between the dielectric constant
Mindess, S., and J. F. Young (1981) Concrete. Engle-
and water content of a concrete has been devel-
wood Cliffs, New Jersey: Prentice-Hall.
oped. This relationship, a second-order polyno-
Mironov, S.A. (1977) Theory and methods of win-
mial, is considered valid for the Denver Interna-
ter concreting. USA Cold Regions Research and
tional Airport concrete pavement. The equation,
Engineering Laboratory, Draft Translation 636.
shown above, is appropriate for volumetric water
contents between 11 and 4% (5 to 2%, gravimet-
Press, W.H., B.P. Flannery, S.A. Teukolsky, and
ric), which encompass a wide range of pavement
W.T. Vetterling (1986) Numerical Recipes: The Art of
field conditions. Because the results showed that
Scientific Computing. New York: Cambridge Uni-
the TDR readings were different between mortar
versity Press.
and concrete and that aggregate size may affect
Topp, G. C., J. L. Davis, and A. P. Annan (1980)
readings, a family of curves may be more appro-
Electromagnetic determination of soil water con-
priate for concrete. Thus, we hesitate to recom-
tent: Measurement in coaxial transmission lines.
mend these results for other concretes until addi-
Water Resources Research, 16(3): 574582.
tional studies are done on concretes of other mix-
ture proportions.
7
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