The relative increase in compressive strength of 20% of
BA blended concretes compared to control concrete for
all ages of curing is shown in Fig. 7. It can be seen that
relative increase in compressive strength attains the maximum
value (24.5%) at 7 days curing. At 14, 28 and 90
days, the relative increase in strength decreases. This
confirms the fact that concrete with BA up to 20% develops
early compressive strength as compared to control
concrete specimens. The reasons for early compressive
strength development of BA concretes and increase in
compressive strength up to 20% cement replacement of
BA may be due to silica content, fineness, amorphous
phase, specific surface area, degree of reactivity of BA
and pozzolanic reaction between calcium hydroxide and
reactive silica in BA in the alkaline environment as
reported by previous works [17–22]. At 25% and 30% of
BA, the strength decreases to lesser value when compared to that of control specimens. Therefore 20% BA seems to
be the optimal limit.