15-09-2016, 11:04 AM
A Partial Replacement for Coarse Aggregate by Seashell and Cement By
Flyash In Concrete
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Abstract- In developing countries where concrete is
widely used, the high and steadily increasing cost of
concrete has made construction very expensive. This,
coupled with the deleterious effect of concrete
production on the environment has led to studies on
various materials which could be used as partial
replacement for coarse aggregate and cement. This
project is experimented to reduce the cost of concrete.
In this research work experiments have been conducted
with collection of materials required and the data
required for mix design are obtained by sieve analysis
and specific gravity test. Sieve analysis is carried out
from various fine aggregates (FA) and coarse
aggregates (CA) samples and the sample which suits the
requirement is selected. Specific gravity tests are
carried out for fine and coarse aggregate. In this
project, cement is replaced with fly ash of about 25%
along with the partial replacement of coarse aggregate
with seashell. The coarse aggregate is replaced with 10
%, 20%, and 30% by seashell. The design mix used to
execute this project is M20 grade concrete. This M20
grade concrete is designed as per Indian Standard Code
for both the conventional concrete and seashell
concrete. The water cement ratio is maintained for this
mix design is 0.5. Preliminary test comprising sieve
analysis, specific gravity, consistency, setting time and
soundness were conducted .workability and strength
test were also carried out on fresh and hardened
concrete made from the study material. The strength
obtained from seashell concrete is compared with the
conventional concrete. Finally to compare both normal
concrete and conventional concrete. Thus, 10%, 20%
replacement of seashell are recommended for
conventional concrete to increase the strength of
concrete and slightly decreased by 30% strength of
concrete to compare the normal concrete.
Keywords: cement, aggregate, fly ash, seashell (ss).
I.INTRODUCTION
As concrete is ubiquitous and its history can
be traced to ancient Egypt and Rome, it is often
falsely perceived as a "simple" material. Actually, the
microstructure of concrete tends to be highly
complex. Moreover, the structure and the properties
of this composite material can change over time. Most modern concrete structures are reinforced with steel,
since concrete itself displays relatively low strength
when loaded in tension. While steel reinforced
concrete is obviously a widely used, cost-effective
construction material, degradation of such structures
has become a major problem in many parts of the
world. The basic constituents of concrete are cement,
water and aggregate (and selected additives). Cement
is produced by heating limestone and clay to very
high temperatures in a rotating kiln. Cement is
produced by grinding the resulting clinker to a fine
powder. Water reacts chemically with cement to form
the cement paste, which essentially acts as the "glue"
(or binder) holding the aggregate together. The
reaction is an exothermic hydration reaction. The
water cement ratio is an important variable that needs
to be "optimized". High ratios produce relatively
porous concrete of low strength, whereas too low a
ratio will tend to make the mix unworkable.
Aggregates are usually described as inert "filler"
material of either the fine (sand) or coarse (stone)
variety. Aggregate tends to represent a relatively high
volume percentage of concrete, to minimize costs of
the material. Recent investigation of Indian sea shells
has indicated greater scope for their utilization as a
construction material. Greater utilization of sea shells
will lead to not only saving such construction material
but also assists in solving the problem of disposal of
this waste product. In present generation as the
population is increasing rapidly and construction
work is also increasing so to replace the old process
the new bricks like fly ash bricks came in to field
replacing the old lime bricks, whereas the cementing
material like mud, lime paste and gums is replaced by
the Cement of different kinds in different
construction. As the status of living is increasing their
needs for maintenance is also increasing more
structures and more vivid types of structures have
come to world. So the need for the replacement of the
present material that is the concrete manufacturing
has to be changed to meet the needs of the structures.
So the most economical, ecological, light – weight
and increasing the ease of work construction of the structure is important in the present economy. So the
role of the light – weight concrete has come into the
field. As modern engineering practices become more
demanding, there is a corresponding need for special
types of materials with novel properties. Scientists,
engineers and technologists are continuously on the
searching for materials, which can act as substitute for
conventional materials or which possess such
properties as would enable new designs and
innovations resulting in to economy, so that a
structure can be built economically. Many attempts
have been made to develop new materials, which is
the combination of two or more materials. Such
materials are called composite materials. Concrete
can be concluded as a composite material as it is a
mixture of different materials. For reducing the cost
of concrete, greater use of pozzolanic materials like
fly ash and blast furnace slag was suggested for the
cement, sea shells, glass and ceramic material are
used in case of fine aggregates, when coming to case
of course aggregates palm kernel shells, coconut
shells and sea shells. The use of these materials as the
substitute material in concrete would reduce the
disposal problem now faced by thermal power plants
and industrial plants, agricultural areas and at the
same time achieving the required strength of concrete.
Already many investigations have been going on the
partial replacement of coconut shells in place of
coarse aggregate. In the present investigation sea
shells has been used as partial replacement of coarse
aggregate and cement by fly ash. Seashells are also
available in large quantities. Tan et al [1] He
analyzed that the Supplementary materials such as fly
ash, slag and silica fume when used in concrete
production have been found to be beneficial in
improving several properties including strength (as a
result of pozzolanic reaction) and permeability (as a
result of reduction in porosity and refinement of the
microstructure) thereby reducing ingress of water and
other harmful salt solutions and in many cases
reducing the overall production cost. Strength
improvements due to the addition of mineral
admixtures is due to the pozzolanic reaction taking
place, which typically starts after seven days and
causes in increase in the amounts of C-S-H gel which
is known to be the strength imparting component in
concrete. Studies have also shown that a combination
of fly ash and slag improves the strength of concrete
at all ages similar to the addition of silica fume.
Gunasegaram[2] studied the properties of concrete
using coconut shell as coarse aggregate were
investigated in an experimental study. Compressive, flexural, splitting tensile strengths, impact resistance
and bond strength were measured and compared with
the theoretical values as recommended by the
standards. The bond properties were determined
through pull-out test. Coconut shell concrete can be
classified under structural lightweight concrete.O.T.
Olateju [3] in his paper reports the exploratory study
on the suitability of the periwinkle shells as partial or
in concrete works. Physical and mechanical properties
of periwinkle shell and crushed granite were
determined and compared. A total of 300 concrete
cubes of size 150 × 150 ×150 mm with different
percentages by weight of crushed granite to
periwinkle shells as coarse aggregate in the order
100:0, 75:25, 50:50, 25:75 and 0:100 were cast, tested
and their physical and mechanical properties
determined. A.P. Adewuyi and T. Adegoke[4]
Concluded The strength of periwinkle shell concrete
is determined based on the properties of the shells and
various percentage replacements; Concrete with
35.4% and 42.5% periwinkle shells inclusion can still
give the minimum 28-day cube strength values of 21
N/mm2 and 15 N/mm2 expected for concrete mixes
1:2:4 and 1:3:6, respectively. Concrete having up to
50% periwinkle shells inclusion can still be regarded
as normal weight concrete. Savings of about 14.8%
and 17.5% can be achieved by adopting 35.4% and
42.5% periwinkle inclusion for 1:2:4 and 1:3:6
concrete mixes, respectively. Nasser et alHe analyzed
that lower replacement levels of cement with fly ash
or slag in the range of 20-35% is optimum in order to
have satisfactory durability to frost conditions.
Concrete with higher water to binder (w/b) ratio is
more susceptible to problems related to deicer salt
scaling and internal micro cracking due to freeze and
thaw cycles. Also, problems of dispersion of the airentraining
agents due to high carbon contents in the
fly ash have been reported. Researchers have argued
that as long as sufficient air content and spacing
factor is provided, high carbon contents in fly ash do
not pose a problem.