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TECHNICAL PAPER

Table 3: Optimum dosage from mini slump test and
yield stress / plastic viscosity for pastes designed
for SCC with different w/b [8]

w/b (BY MINI OPTIMUM YIELD PLASTIC
VOLUME) SLUMP DOSAGE (% STRESS VISCOSITY
SPREAD BWOB) (Pa) (mPa.s)
(mm)
0.8 178 0.21 0 533
0.9 170 0.18 1.75 313
1.0 169 0.16 1.18 244
1.1 166 0.14 1.82 194
1.2 174 0.12 2.19 146

Figure 8: Relation between C u and packing density
[3]
(based on the study reported in )
Once the selection of the binder combination and SP/
VMA dosage is completed, the other primary component in
designing SCC is the choice of the blend of aggregate. For
this purpose, the concept of packing can again be applied.
As described in , an experimental approach can be used to
[3]
determine the extent of voids for a particular combination of
coarse, medium and fine aggregates. However, as the number
of trials to perform a complete set of experiments would be
too many, an optimization approach can be applied. Further,
the number of combinations can be brought down significantly
Figure 6: Spherical particle of aggregate suspended in a liquid medium by using a minimum of 40 % (and a possible maximum of
(based on )
[11]
60 %) fine aggregate in the blend, as that would be most
practical. However, for a one off design, when the aggregate
optimum dosages of the VMA were determined to be 0.007,
characteristics change often, it is possible to use a parameter
0.011, 0.014, and 0.021 for the pastes with w/b of 0.9, 1.0, 1.1 from the particle gradation of the aggregate to describe the
and 1.2 respectively. Using the optimum dosage of SP and ideal combined gradation. The work of Nanthagopalan and
VMA, concrete mixtures were designed for the assessment of Santhanam showed that the packing density of aggregate
[3]
segregation resistance, and the results are presented in Figure 7 is well related to the coefficient of uniformity of the blended
(from [11] ). It is clear from the results that for optimal dosages of aggregate, as shown in Figure 8.
SP and VMA, all concrete trials resulted in a non-segregating
mixture. Once the paste design is optimized with the correct dosage of
the SP and VMA, and the aggregate combination is yielding the
best packing density, the performance of the SCC can be better
controlled to yield the right flowability properties, as indicated
in Table 4. The result clearly indicates that for SCC designed

Table 4: Influence of packing density on flow and
strength, for SCC with fixed paste content of
3
388 litres/m and w/b of 1.0
PROPORTIONS OF PACKING SLUMP SLUMP COMPRESSIVE
AGGREGATES (BY DENSITY FLOW FLOW STRENGTH
VOL.) (mm) WITH J (MPa)
FA : CA 12.5 mm : RING (mm)
CA 20 mm
40 : 50 : 10 0.64 420 380 40.5
Figure 7: Concrete behavior at different SP and VMA dosages (from ) 40 : 30 : 30 0.66 500 465 42.7
[11]
– concretes designed with VMA dosages at or above optimum
show no segregation 40 : 10 : 50 0.68 615 600 45.6

54 THE INDIAN CONCRETE JOURNAL | JANUARY 2026