Making concrete structure without compaction has
been done in the past. Like placement of concrete underwater by the use of
termie without compaction. Inaccessible areas were concreted using such
techniques. The production of such mixes often used expensive admixtures and
very large quantity of cement. But such concrete was generally of lower
strength and difficult to obtain. This lead to the development of Self
Compacting Concrete (SCC). The workability properties of SCC such as filling
ability, passing ability and segregation resistance are evaluated using
workability tests such as slump flow, V funnel and L-Box tests.
The present work deals with addition of Nano-silica
to concrete as partial replacement to cement in dosages of 1%, 1.5% and 2% by
weight of cement. Based on early research M25 grade concrete has
been chosen for this work. The mix design was prepared using IS: 10262-2009 Guidelines
for concrete mix design proportioning. In the present work 24 numbers of cube moulds
and 12 numbers of cylinder moulds were casted with addition of Nano-silica with
different proportions which are tested for compressive strength and split
tensile strength. Addition of Nano-silica to normal cement concrete show increase
in compressive strength and decrease in splitting tensile strength.
The compressive strength of
cement concrete can be increased considerably by the addition of Nano-silica.
Based on the experimental results, use of Nano-Silica as partial replacement of
cement in small quantities is advantageous on the performance of concrete.
Nano-Silica added in small quantities can improve the compressive strength. The
increase in various strength characteristics of concrete containing nano-silica
content can be due to the availability of additional binder in the presence of
nano-silica. Nano silica has high amorphous silicon dioxide content. The
Portland cement in concrete releases calcium hydroxide during the hydration
process. The nano silica reacts with the calcium hydroxide to form additional
binder material. The availability of additional binder leads to increase in the
paste-aggregate bond, results improved strength properties of the concrete
prepared with nano-silica combination.
Keywords: Self Compacting Concrete, flow ability, passing
ability, nano silica, superplasticizer.