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28-day age, all mixes showed strengths higher than the design strength of
5,000 psi.
Also, all fly ash concrete mixes showed strengths higher than the control mix,
with the 40% cement replacement concrete showing the highest strength.
At the 56 and 91-day ages, the trend continued with the 50% cement
replacement concrete showing the highest strength. Even the 60% replacement
concrete showed 38% higher strength compared to the control mix at the 91­
day age.
Conclusions: 3000 psi; 4000 psi and 5000 psi Concrete
In conclusion, these tests establish that good quality structurally strong
concrete can be made with high cement replacements by fly ash. Even 50 and
60% replacements showed higher strengths than the control mixture at 56- and
91-day ages. But this level of cement replacement with fly ash generally will
not be made for structural grade concrete for flexural members, such as beams
where rapid form stripping is required.
However, these higher replacements may be used for mass concrete where
early age strength levels are not needed. At the 40% cement replacement
level, the strength levels at early ages are within acceptable limits and can be
used for structural grade concrete.
Therefore, it can be concluded that fly ash from Pleasant Prairie Power Plant
can be used in the manufacture of structural grade concrete with cement
replacement levels of up to 40%, on a 1.25 to 1 fly ash to cement weight basis
replacement ratio.
The following figures and tables show strength versus age and give the test
data.
AVERAGE COMPRESSIVE STRENGTH, PSI
7000
6000
5000
4000
3000
2000
1000
P4-1
P4-2
P4-3
P4-4
P4-5
P4-6
0
0 10 20 30 40 50 60 70 80 90 100
AGE, days
Figure 4–1: Compressive Strength vs. Age Comparison – Mix Nos. P4-1 through P4-6
We Energies 58
Coal Combustion Products
Utilization Handbook