Study On Partial Replacement Of Fine Aggregates In Concrete By Recycled Concrete Aggregates

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
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Study On Partial Replacement Of Fine Aggregates In Concrete By
Recycled Concrete Aggregates
Prof. Preethi AV1, Dr. Rajendra S 2, Mr. Sanjay HN 3
1Assistant Professor, Department of Civil Engineering, Vijaya Vittala Institute of Technology, Bengaluru,
Karnataka, India
2 Principal, Vijaya Vittala Institute of Technology, Bengaluru, Karnataka, India
3 Student, Department of Civil Engineering, Vijaya Vittala Institute of Technology, Bengaluru, Karnataka, India
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Abstract - In order to produce the concrete, a significant
amount of natural resources are needed, particularly in the
developing nations like India where urbanization and
infrastructure development are on therise. Thefineaggregate
is one such resource. Due to the gradual depletion of natural
sand resources and the major issues they pose to both the
environment and humanity, it has led to the exploration for
other acceptable alternatives. The present work investigates
about the development of a novel construction material by
utilizing Recycled Concrete Aggregate(RCA)assubstitutionof
natural fine aggregates in the production of concrete. The
replacement is done from 0% to 30% at an interval of 5%. The
grade of concrete used is M20 and w/c ratio maintained is 0.5.
The experimental investigations have been done to examine
the effect of RCA on the characteristics of concrete, including
workability, compressive strength, split tensile strength and
flexural strength. The results oftheexperimentalinvestigation
depict that the workability of the concrete reduces with
increase in percentage of RCA and the optimum replacement
of fine aggregates by RCA is 25%.
Key Words: Construction, Concrete, Fine Aggregates,
Workability, Strength.
1. INTRODUCTION
The combination of cement, fine aggregates, coarse
aggregates and water make up concrete and depending on
the requirements, admixtures or fibers or otheradditivesare
also added. It's a heterogeneous composite and without a
doubt, the most frequently utilized construction material in
the whole world. A semi-fluid mass may be created in the
presence of these components and can be molded into any
desired shape. Using proper curing techniques, concrete is
turned into a hard solid material that may survive for
hundreds of years. The versatility, dependability and
sustainability of concrete, as well as its strength, rigidity,
durability, mouldability, efficiency and economy are reasons
for its widespread use in the construction sector.
In influencing the fresh and curing properties, mix
proportions and costs of concrete, the fine and coarse
aggregates that make up 60 to 70 percent of the volume are
critical factors. Aggregate qualityand type are crucial factors
in concrete construction, since they are the basic building
blocks of the finished project.Gravel andstoneareoftenused
in concrete as coarse aggregates, whereas river sand or
natural sand is generally benefitted as fine aggregates. River
sand, a granular substance made up of fragmented rock and
mineral particles that occurs naturally. Sand from the river
has the potential to replenishitself. Silica(silicon dioxide), in
the form of quartz, accounts for the majority of the sand's
composition, due to its chemical inertness and substantial
hardness. The cost of natural sand grows as the supply
diminishes near the point of consumption, increasing the
entire building cost. Findinganalternatematerialthatfitsthe
technical criteria of fine aggregate and its wide accessibility
would help ensure long-term infrastructure expansion. Civil
engineers have been conducting a broad variety of studies in
an effort to locate an alternative supply of fine aggregates.
The bulk of the world's infrastructure is built using
concrete. As a consequence of the many concrete structures
have started to deteriorate due to the complicated
interactions between concrete and its surrounding
environment, as well as the lack of routine maintenance,
concrete recycling is becoming increasingly popular when
concreteconstructionsareremovedorrepaired.Itispossible
to ensure the long-term viability of concrete structures by
concrete recycling. Many locations can provide recycled
concreteaggregates. Demolitionwasteandprecastconcretes
are the most common sources of these aggregates. Recycled
concrete aggregates may be made from many crushing of
concrete debris. Cementitious renderings and masonry
mortars as a natural sand alternative, road construction and
filler material forgeo-synthetic reinforced buildings and soil
stabilization are all examples of low-grade applications
where they are now employed.
2. METHODOLOGY
The various methods that are employed in this study are
as follows.
 The materials needed for the developmentofconcrete,
including cement, river sand, RCA, and coarse
aggregates are obtained from various sources.

 The procured materials are subjected to basic testing
in the laboratory.
 The mix design for concrete grade M20 is performed in
accordance with IS: 10262-2009, with a w/c ratio of
0.5.
 The various mix combinations are determined by
replacing a portion of the fine aggregates in concrete
with RCA at 0%, 5%, 10%, 15%, 20%, 25%, and 30%.
 Before casting the specimen, the workability of
concrete is examined in accordance with IS: 1199-
1959.
 The specimens are casted on various mix
combinations and cured in accordance with the test
requirements.
 The compressive strength test is performed in
accordance withIS:516-1959on150mm*150mm*150
mm cube specimens cured for 3 days, 7 days, and 28
days.
 The split tensile strength is performed according to
IS:5816-1999 on cylindrical specimens with a
diameter of 150mm and a height of 300mm that cured
for 3 days, 7 days, and 28 days.
 The flexural strength is performed on 100mm*
100mm*500mm beam specimens cured for 28 days
according to IS: 516-1959.
3. MATERIALS
3.1 Cement
In a broader sense, cement refers to any adhesive
substance, but in more specific it refers to the binding
material used in building and civil engineering projects. The
cement is made of fine powder, that when combined with
water, solidify to form a solid mass. Hydration, the chemical
reaction of the cement compounds with water to produce
minute crystals or a gel like substance with a large surface
area, is what causes setting and hardening. Constructional
cement, which will even set and solidify under water, are
frequently referred to as hydraulic cements because of their
hydrating qualities. Of these, Portland Cement is the most
significant. The OPC cement of Ambuja of grade 53 in
accordance to IS: 12269-1987 is utilized throughout the
study. The basic properties of cement are given in the below
table 1.
Table -1: Properties of Cement
Sl. No. Properties Results
1 Specific Gravity 3.09
2 Standard Consistency 36%
3 Initial Setting Time 35 min.
4 Final Setting Time 360 min.
3.2 Fine Aggregates
Natural sand which is predominately utilized as fine
aggregates, which is a key component of concrete. The
hardened properties of the concrete are significantly
impacted by the quality and fine aggregate density. By
choosing fine aggregates based on grading zone, particle
form, surface texture, abrasion and skid resistance, one can
increase the strength, durability and affordability of the
concrete or mortar combination. The structural filler in
concrete mix formulas that takes up the majority of the
volume is fine aggregate. The significant outcome may be
affected by varying the composition, shape, size and other
characteristics of fine aggregate. The natural sand that is
readily available in the area is utilized. The size of the fine
aggregates passing through 4.75mm is considered. Tests
were carried out in accordance withIS2386(PART3)-1963.
The basic properties of natural sand are given in the below
table 2.
Table -2: Properties of Fine Aggregates
2 Sieve Analysis 2.67
3 Bulking 4%
3.3 Coarse Aggregates
Stone that has been shattered into small pieces and is
shaped erratically are considered as coarse aggregates. In
construction projects, aggregates like limestone,graniteand
river aggregate are used. Although there are numerous
elements or components used to make concrete mix, coarse
aggregates account for the majority of the mix volume and
are one of its most important constituents. The majority of
the times, these aggregates are obtained by blasting at stone
quarries, breaking them by hand, or using crushing
equipment. The coarse aggregate utilized in this project has
a maximum size of 20mm. The tests were carried out
according to the protocol outlinedinIS2386(PART3)-1963.
The basic properties of coarse aggregates are given in the
below table 3.

Table -3: Properties of Coarse Aggregates
SN. Properties Results
3 Water Absorption 0.45%
3.4 Recycled Concrete Aggregates
Multiple crushing of destroyed concrete yields the
recovered fine aggregates needed for new concrete
construction. For this project, 150 micron retained sieve
aggregates are employed. The properties of RCA aregiven in
the table 4.
Table -4: Properties of RCA
2 Bulking 9%
3.5 Water
Cement is mixed with water since it is the most cost
effectiveandappropriatecomponent.Whenmakingconcrete,
it is important to use water that is free of any dangerous
impurities, such as oil or alkalis or acids. In general, only
potable is importantthatthemanufactureofconcreteinclude
the usage of water. So long as the pH of the water remains
constant is within the range of 6.5 to 8.5 and the organic
materials are removed, it may be utilized to produce
concrete.
3.6 Mix Design
The mix design of concrete with M20 grade is carried out
as per IS:10262-2009. The water to cementratiomaintained
is 0.5. The obtained mix proportions are given in the table 5
and various mix designations are given in the table 6.
Table -5: Mix Proportion
Sl. No. Materials Proportion Weight (Kg/m3)
1 Cement 1 394.3
2 Fine Aggregates 1.58 624.9
3 Coarse Aggregates 2.93 1157
4 Water 0.5 197
Table -6: Mix Designation
Sl. No. Mix Designation
1 R0 0% RCA Replacement
4. RESULTS AND DISCUSSIONS
4.1 Workability Test
The results of the slump cone test of concrete are given
in the table 7. It can be observed that the workability of the
concrete decreases with increase in percentage of RCA. This
trend is observed because the water absorption of RCA is
more when compared to the natural sand. The graphical
results of workability test are given in the chart 1.
Table -7: Workability Test Results
Sl. No. Mix Designation Slump Value(mm)
1 R0 108
2 R1 107
3 R2 105
4 R3 103
5 R4 101
6 R5 98
7 R6 97
R0 R1 R2 R3 R4
Chart -1: Workability Test Results

4.2 Compressive Strength Test
The results of compressive strength test are given in
the table 8. The compressivestrengthat28daysishighestfor
R3 i.e., 29.33 N/mm2 and strength is increased by 6.42%
when compared to conventional concrete R0. The
compressive strength increases upto R3 and further rise in
RCA reduces the concrete’s compressive strength. It can also
be seen that the compressive strength of R4 is slightly higher
compared to the conventional concrete R0 and has the
satisfactory results. The graphical results of compressive
strength are shown in the chart 2.
Table -8: Compressive Strength Test Results
Sl. No. Mix
Designation
Compressive Strength(N/mm2)
3 Days 7 Days 28 Days
1 R0 18.32 22.35 27.56
2 R1 18.78 23.44 27.95
3 R2 19.32 24.67 28.44
4 R3 20.88 25.22 29.33
5 R4 19.64 24.33 28.20
6 R5 18.20 22.28 27.22
7 R6 17.67 22.12 26.20
Chart -2: Compressive Strength Test Results
4.3 Split Tensile Strength Test
The results of the split-tensile strength test are given
in the table 9. The split-tensile strength is highest for R3 i.e.,
4.08 N/mm2 and strength is increased by 9.1% when
compared to the conventional concrete R0. The further
increase in percentage of RCA reduces the tensile strength of
concrete. It can be observed that the split tensile strength of
R5 also has satisfactory results compared to theconventional
concrete R0. The graphical results of the split tensile strength
are drawn in the chart 3.
Table -9: Split Tensile Strength Test Results
Sl. No. Mix
Designation
Split-tensile Strength(N/mm2)
3 Days 7 Days 28 Days
1 R0 2.61 2.97 3.74
2 R1 2.68 3.04 3.82
3 R2 2.75 3.11 3.96
4 R3 2.78 3.16 4.08
5 R4 2.56 2.89 3.92
6 R5 2.48 2.75 3.86
7 R6 2.40 2.68 3.72
Chart -3: Split Tensile Strength Test Results
4.4 Flexural Strength Test
The results of flexural strength test aregiveninthetable
10. The flexural strength of conventional concrete R0 at 28
days is 5.87 N/mm2. The R3 has the highest flexural strength
of 6.37 N/mm2 at 28 days which is 8.5% more when
compared to the R0. It can be observed that R5 hasresultthat
is satisfactory to R0. The graphical resultsofflexural strength
test are given in the chart 3.
Table -10: Flexural Strength Test Results
SN. Mix Designation Flexural Strength(N/mm2)
1 R0 5.87
2 R1 6.12
3 R2 6.25
4 R3 6.37
5 R4 6.18
6 R5 5.92
7 R6 5.76

Chart 4: Flexural Strength Test Results
5. CONCLUSIONS
The conclusions that can be drawn from the study are as
follows.
 The workability of the concrete decreases with
increase in percentage replacement of RCA.
 The R3 has the highest compressive strength of 29.33
N/mm2 at 28 days which is 6.42% more when
compared to the R0.
 The highest split-tensile strength of 4.08 N/mm2 is
examined for R3 which is 9.1% more when compared
to the R0 at 28 days.
 The flexural strength at 28 days is highestfor R3 which
is 8.5% more when compared to the R0.
 The optimum replacement of fine aggregates by RCA
in concrete is 15%.
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Study On Partial Replacement Of Fine Aggregates In Concrete By Recycled Concrete Aggregates

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