Effects of Ground Granulated Blast Furnace Slag in Portland Cement ...

Results of the SAI tests indicate low variability (Figures 1 to 4). Each monthly sample
deviates little from the 7-day and the 28-day averages for a given cement. GGBFS from this
particular ready-mix company appears to be quite stable when examining the results from
particle distribution, specific surface, chemical composition, and activity tests.
Figure 5 shows the differences in SAI among the different cements at 7 and 28 days for the
research GGBFS. Most specimens passed the minimum average SAI set forth by ASTM
C989 for 7 and 28 days. Cement A did not meet the minimum 28-day SAI of 95. It was near
the minimum with a SAI of 92. The 7-day averages were close to each other for all the
cements. Separation by compressive strength of the cements occurred at 28 days. Cement C
was clearly the strongest followed by B, D, and A. The reference cements met the strength
requirements of ASTM C989 as shown in Table 8 but only Cement C fell in the required
alkali range.
120
100
Activity Index
80
60
40
7 day
28 day
7 day average
28 day average
20
0
Research
Aug-02
Sep-02
Oct-02
Nov-02
Dec-02
Month
Jan-03
Apr-03
May-03
Jun-03
Jul-03
Figure 1. Monthly Sample Slag Activity Index for Cement A
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