Reduction in the peak temperature
The percentage of reduction in the peak temperature (Prp) for each mix with
pozzolan was calculated using the following equation.
Prp=(Tcm- Tpm)/ Tcm Equation 5-1
Where:
Prp : Percentage of reduction in the peak temperature,
Tcm: Peak temperature of the control mix (the mix with plain cement),
Tpm: Peak temperature of the mix with pozzolan (20% fly ash, 35% fly ash, 50%
slag, 70% slag)
Using Prp eliminates the possible errors in the peak temperatures recorded by the
Sure Cure system because all the mixes were made and tested in the same condition. The
ratio between peak temperatures should therefore be correct even if an error exists in the
peak temperature number. In 5-5, Prp for different mixes is shown. The numbers could be
averaged because both cements A and B are Type II AASHTO cement.
Table 5-5 Effect of Pozzolans on the Peak Temperature of Concrete
Placing % Reduction in Peak Temperature (at 14 days)
Cement Source
Temperature 20% Fly Ash 35% Fly Ash 50% Slag 70% Slag
A 73F 12.7 17.2 8.2 21.2
B 73F 8.5 26.1 14.1 24.1
Average for Cements A & B 10.6 21.7 11.2 22.7
A 950F 1.9 8.0 0.1 23.4
B 950F 9.7 18.6 4.6 7.0
Average for Cements A & B 5.8 13.3 2.4 15.2
In Figures 5-5 and 5-6, the effect of using pozzolans on temperature at different
ages of concrete is shown. The percent of reduction in temperature (Pr ) was calculated
as:
Pr=(Tc- Tp)/ Tc
Equation 5-2