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Table 4-53: Compressive Strength of Concrete Mixture
Mixture
No.
Fly Ash
Content, %
[FA/(C+FA)]
Compressive Strength (psi)
3-day 16-day 28-day 42-day
Act. Avg. Act. Avg Act. Avg. Act. Avg.
-- 80 145 1265 1345
CON-C 42 -- -- 50 60 145 135 1355
-- 50 120 1410
Electrical Properties
The electrical resistivities obtained for the concrete Mixture CON-C are given
in Table 4-54 and Figure 4-29. Overall, resistivities of both air-dried and
saturated specimens were comparable with, approximately 40 to 50 ohms-cm
at the age of 16 days and 60 to 70 ohms-cm at the age of 42 days. Although
the compressive strengths were much lower for the Mixture CON-C than a
typical concrete used for many construction applications, the lower resistivity
values achieved through the incorporation of high-carbon fly ash and carbon
fibers are very promising for potential grounding applications. Further
refinement of the carbon fiber content to optimize the resistivity and strength
properties of the concrete is needed as a part of future laboratory studies. The
permeability values show only a slight increase between 16 and 28 days. The
relative electrical permeability of air-dried and saturated specimens were
typically within 1.01.
For CON-C, air-dried specimens also had a higher electrical resistivity at the
age of 42 days, but the difference between saturated and air-dried specimens
were much less. Typically the difference between air-dried and saturated
specimens was 10 ohm-cm or less. This may be attributed to the conductivity
of the carbon fibers used in the mixtures.
127 We Energies
Coal Combustion Products
Utilization Handbook