Civil Engineering Reference
In-Depth Information
The amounts of fine and coarse aggregates not used
are recorded on the data sheet in Column 3, and mass of
aggregates used (Column 2 minus Column 3) are noted in
Column 4. If the slump when tested had been greater than
that required, additional fine or coarse aggregates (or
both) would have been added to reduce slump. Had the
slump been less than required, water and cement in the
appropriate ratio (0.45) would have been added to in-
crease slump. It is impor-
tant that any additional
quantities be measured
accurately and recorded
on the data sheet.
Mixture Proportions.
Mixture proportions for
a cubic meter of concrete
are calculated in Column
5 of Fig. 9-6 by using the
batch yield (volume) and
density (unit weight).
For example, the number
of kilograms of cement
per cubic meter is deter-
mined by dividing one
cubic meter by the
volume of concrete in
the batch and multi-
plying the result by the
number of kilograms of
cement in the batch. The
percentage of fine aggre-
gate by mass of total
aggregate is also calcu-
lated. In this trial batch,
the cement content was
341 kg/m
3
and the fine
aggregate made up 38%
of the total aggregate by
mass. The air content
and slump were accept-
able. The 28-day strength
was 39.1 MPa, greater
than Â. The mixture in
Column 5, along with
slump and air content
limits of 40 (±20) mm
and 5% to 8%, respec-
tively, is now ready for
submission to the project
engineer.
Fig. 9-6. Trial mixture data sheet (metric).
Table 9-13. Example of Results of Laboratory Trial Mixtures (Metric)*
Fine aggregate,
Air content,
Density,
Cement
percent of total
Batch no.
Slump, mm
percent
kg/m
3
content, kg/m
3
aggregate
Workability
1
50
5.7
2341
346
28.6
Harsh
2
40
6.2
2332
337
33.3
Fair
3
45
7.5
2313
341
38.0
Good
4
36
6.8
2324
348
40.2
Good
*Water-cement ratio was 0.45.
