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TECHNICAL PAPER

Figure 2: Ideal grading curve for q = 0.26 and actual overall particle size Figure 3: Finalized cementitious material quantities for the mixtures
distribution for the mix DM1

were prepared in which the combined granular gradation This substantial reduction in cement content for high strength
was adjusted to meet the ‘ideal’ gradation suggested by the and durable concretes has obvious benefits in respect of
model (‘q’ value was chosen between 0.26 and 0.27). One cost. More important, however, is the reduction in cement
such gradation is shown in Figure 2, for mix DM1, which had consumption, which would lead to a decrease in the release
a combination of quartz powder and silica fume. The finalized of CO 2 and global warming. The reduced cement content in
cementitious material quantities for the mixtures are presented concrete also implies reduced heat of hydration. While the
in Figure 3, while the primary results are tabulated in Table 2. For benefits of particle packing are clearly evident from the study,
all the concretes, the SP dosage was adjusted to obtain a slump it should be noted that the design of complex systems like self-
compacting concrete or 3D printed concrete also involves the
of 80-100 mm, retained for 1 hour after mixing.
control of the rheology of the mixture. This aspect cannot be
From Figure 3 and Table 2, it is apparent that the binary addressed by particle packing alone. The subsequent studies
blended mixtures with quartz powder and fly ash were able to describe how a combination of particle packing and rheology
almost match the strength performance of the control mixture can be applied to the mixture design of such concretes.
CEM, while the mixture with microsilica showed a significantly
improved performance owing to the ability to provide particles 3. BINDER SELECTION AND AGGREGATE
in the 0.1-1 µm range, as evident from Figure 2. The same effect OPTIMIZATION FOR SCC
of the fine particles of silica fume is seen in the ternary-blended SCC typically utilizes binary or ternary combinations of
systems DM1 and DM2, which were designed to get as close cementitious materials in order to reduce the quantity of
as possible to the ideal gradation. In these two cases, even plain cement, and to satisfy the need of a high binder content
3
with cement contents of 270 and 240 kg/m respectively, the to provide stability to the flowable concrete. In most cases,
performance was significantly improved over the control mixture. fly ash is an ideal replacement material for cement in SCC.
While the extent of fly ash replacement is regulated by
The durability parameters, namely Chloride permeability (RCPT codes and specifications, it is often advantageous to utilize
- charge passed less than 500 Coulombs) and Water Penetration the maximum quantity to extend the binder as well as bring
(WPT) were also improved noticeably in the mixtures with about a good control on the flow properties. One potential
reduced cement content which included microsilica, that were question therefore could be how to rationalize the extent of
proportioned to match the modified Andreassen ideal particle replacement. A possible answer to this lies in exploring the use
packing curve (DM1 and DM2). of particle packing experiments to determine the proportion of

Table 2: Strength and durability parameters for concretes in the study reported in [6]
CEM QPM FAM MSM DM1 DM2
Compressive strength (MPa) at 28 days 67 67 61 78 82 71
Flexural strength (MPa) at 28 days 4.9 5.5 4.3 7.3 6.8 5.2
Water penetration (mm) as per DIN 1048 12 11 10 7 6 6
Charge passed (Coulombs) as per ASTM C1202 2500 2100 1400 400 450 400

52 THE INDIAN CONCRETE JOURNAL | JANUARY 2026