4. Test results of marble dust blended cement
4.1. Water requirements and setting times
Fig. 3 shows the standard water requirement needed to produce
standard cement paste according to the E.S.S. 2421-1993. From this
figure it is observed that there is no obvious variance in water
requirements among samples made with marble dust modified cement
and the control (OPC) sample.
Initial and final setting times of plain and blended cement with
5.0%, 7.5%, 10.0% and 15.0% marble dust are given in Fig. 4. The initial
setting time must be greater than 45 min and the final setting
time must not exceed 10 h (600 min).
From this figure, it can be seen that there is no noticeable effect
occurred when using up to 15.0% marble dust as cement replacement.
Also, all of test specimens comply with the limits of E.S.S.
2421-1993.
4.2. Expansion of cement paste (Le Chatelier method)
Fig. 5 shows the measured expansions for marble dust blended
cement compared to plain cement. From this figure, it is found that
the expansion value is not so much affected by the replacement of
marble dust. Expansion values comply with the limits of E.S.S.
2421-1993,where the allowable expansion should not exceed
10 mm.
4.3. Fineness of cement
The fineness of cement is expressed as the percentage retained
on sieve No. 170 according to E.S.S. 2421-1993 The fineness of
marble dust blended cement is calculated according to replacement
ratios, based on the fineness of plain cement and marble
dust. The calculated retained percentages are given in Fig. 6. From
this figure, the marble dust blended cement has lower fineness
compared with unblended cement.
4.4. Tricalcium aluminate (C3A) content
Fig. 7 represents the calculated tricalcium aluminate (C3A) content
of plain cement and marble dust blended cement. C3A content
was calculated using Bogue equations [13]. Calculations are based
on the chemical analysis of both plain cement and marble dust in
addition to the replacement ratios of marble dust. It is observed
that the higher values of marble dust decreases the C3A content
compared to plain cement. For 15.0% marble dust, C3A decreases
by 10.9% compared to plain cement. This is due to the small
amount of Al2O3 and Fe2O3 in marble dust compared to plain
cement.