a study on recycled concrete aggregates · a study on recycled concrete aggregates pavan p s 1,...
Post on 15-Apr-2020
20 Views
Preview:
TRANSCRIPT
A STUDY ON RECYCLED CONCRETE AGGREGATES PAVAN P S
1, BABITHA RANI H
1,DEEPIKA GIRISH
1, RAGHAVENDRA K M
2,
VINOD P N1,DUSHYANTH.V.BABU.R
1,SHAIK NUMAN1
1Assistant Professor, Department of Civil Engineering, SET, Jain University.
2Student, Department of Civil Engineering, SET, Jain University.
Abstract
The amount of construction waste has been dramatically increased in the last decade, and
social and environmental concerns on the recycling of the waste have consequently been
increased. Many researchers state that recycled concrete aggregates (RCA) are only
suitable for non-structural concrete application. This research, however, shows that the
recycled aggregates that are obtained from concrete specimen make good quality concrete.
Concrete waste from demolished structure has been collected and coarse aggregate of
different percentages is used for preparing fresh concrete. In this study, for the 28th
day
cube compressive strength using OPC; the strength for 25%, 50%, 75% and 100% RCA
mixes were 23.5%, 33.5%, 32.4% and 10.7%, respectively less than 0% RCA mix whereas
for PSC, were 17.8%, 36.7%, 40.6% and 19.1% respectively less than normal concrete.
The cylinder compressive strengths at 28 days for 25%, 50%, 75% and 100% RCA mixes,
using OPC were 37.7%, 32.0%, 33.7% & 28.4% and using PSC were 20.5%, 27.5%,
25.1% & 30.3% respectively less than that of normal concrete mix. However, in split
tensile strength, a continuous decrease in strength was observed with addition of RCA. The
values obtained for 25%, 50%, 75% & 100% RCA, for OPC, were 20.6%, 33.0%, 34.9%
& 42.5% respectively less than 0% RCA concrete while for PSC, were 1.1%, 16.3%,
26.1% & 27.2% less correspondingly. This study proves that, though the strength of
concrete is affected by addition of RCA, the cost saving is upto 16% by 100% substitution
of natural aggregates. Moreover, the use of PSC instead of OPC leads upto 29% reduction
in cost.
Keywords: Recycled concrete aggregates, natural aggregates, compressive strength,
split tensile strength, Ordinary Portland cement, Portland Slag cement.
Introduction
Concrete is globally the most widely used material in the construction industry.
Basically, concrete is a manufactured product consisting of cement, aggregates, water
and admixture. The composition of aggregates forms a major portion of the mixture
consisting of sand, crushed stones and gravel which are inert granular materials.
Construction aggregates make up more than 80 percent of the total aggregate market
and are used mainly for building constructions and pavements. The word concrete
comes from the Latin word ‘‘concretus’’ (meaning compact or condensed), the perfect
passive participle of ‘‘concrescere’’, from the words ‘‘con’’ (together) and ‘‘crescere’’
(to grow). [1]
Fig. 1.1: Stress-Strain Relationship of Ordinary Concrete
International Journal of Pure and Applied MathematicsVolume 118 No. 18 2018, 3239-3263ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu
3239
S
RECYCLED CONCRETE AGGREGATES
Recycled aggregates are aggregates derived from the processing of materials previously used
in construction. Examples include recycled concrete from construction and demolition waste
material (C&D), reclaimed aggregate from asphalt pavement and scrap tyres. Coarse Recycled
Concrete Aggregate (RCA) is produced by crushing sound, clean demolition waste of at least
95% by weight of concrete, and having a total contaminant level typically lower than 1% of
the bulk mass. Other materials that may be present in RCA are gravel, crushed stone,
hydraulic-cement concrete or a combination deemed suitable for pre-mix concrete production.
LITERATURE REVIEW
Sowmya.et.al. (2000), some tests were conducted using the recycled aggregates to study
and compare the results with the naturally available aggregates. The tests were conducted
International Journal of Pure and Applied Mathematics Special Issue
3240
on the aggregates which weren’t subjected to any prior treatment. The impact value for
recycled aggregate was obtained as 35% and that for natural aggregate as 29.9%. The
abrasion value for recycled aggregate was obtained as 47.4% and that for natural aggregate
as 29.6%. Water absorption of recycled aggregate (4.2%) was found to be higher when
compared to the natural aggregate (0.4%). It was found that compressive strength of
concrete made from the recycled aggregate is about 76% of the strength of concrete
made from natural aggregate for normal strength concrete (M20). Flexural strength of
the recycled aggregate concrete is almost 85% and 80% of natural aggregate concrete.
Amnon.et.al (2002), concrete having a 28-day compressive strength of 28 MPa was
crushed at ages 1, 3 and 28 days to serve as a source of aggregate for new concrete,
simulating the situation prevailing in precast concrete plants. The properties of the
recycled aggregate and of the new concrete made from it, with nearly 100% of
aggregate replacement, were tested. The properties of the concrete made with recycled
aggregates were inferior to those of concrete made with virgin aggregates. Effects of
crushing age were moderate: concrete made with aggregates crushed at age 3 days
exhibited better properties than those made with aggregates of the other crushing ages.
Shailendrakumar.et.al. (2004), in this paper, the author found the relationship between
split tensile strength and compressive strength for RCA concrete as well as controlled
concrete. The recycled concrete aggregate used was that passing through IS sieve 40mm
and retained on IS sieve 4.75mm. For controlled concrete the natural stone chips of same
nominal size was used in making concrete. If required a dose of superplasticizer [Conplast
SP 430 (M)] was also added to ordinary tap water to obtain desired degree of workability.
In this study, 3 mixes were prepared i.e. replacement of natural aggregates by 0%, 50%
and 100% RCA. The strength was tested at 28 days maturity of casted concrete. It was
observed that recycled concrete aggregate has lower value of specific gravity and
moderately high values of water absorption, crushing value, impact value and abrasion
value. Furthermore, similar to concrete containing natural aggregate, tensile strength of
recycled aggregate concrete containing recycled concrete aggregate, mainly depends on
compressive strength. Chaurpagar.et.al. (2004), the author investigated physical and
mechanical properties of RCA with and without steel fibres and polymer against
controlled concrete. Specimens (cubes/beams/cylinders) were prepared by varying the
parameters like water cement ratio and volume of polymer (2.5%, 5.0%, and 10% by
International Journal of Pure and Applied Mathematics Special Issue
3241
parts weight of cement) and constant 0.5% steel fibre by volume of concrete. Recycled
Aggregate and Natural Aggregate shows that the former has high specific gravity, high
absorption capacity and low fineness modulus. Resistance to mechanical actions such
as crushing strength, impact value and abrasion value of recycled aggregates are
significantly higher than that of conventional aggregates. There is a marginal increase
in the compressive strength due to the addition of polymer-steel fiber in recycled
concrete. There is significant increase in split tensile strength and flexure strength at 90
days in polymer steel fiber recycled aggregate concrete as compared to conventional as
well as recycled aggregate concrete. Area under stress strain curve is higher, shows the
high toughness properties of concrete that it indicates that polymer concrete is more
suitable for the earthquake resisting structures. It is observed that there is an
improvement in the ductility with addition of 10% polymer & 0.5% steel fiber in the
concrete as compared to recycled aggregate concrete as well as conventional concrete.
Limbachiya.et.al. (2004), the report aimed at examining the performance of Portland
Cement Concrete produced with natural and coarse aggregates. The study showed that
because of attached cement paste in RCA, the density of these materials is about 3-
10% lower and water absorption is about 3-5 times higher than the corresponding
natural aggregates. The results also indicate that for RCA samples obtained from four
different sources, there was no significant variation in strength of concrete at a given
RCA content. Natesan.et.al. (2005), an experimental investigation was conducted to
study the mechanical properties of concrete where natural coarse aggregate is partially
replaced with recycled coarse aggregate. It was concluded that RCA increases the
mechanical properties of conventional concrete and it was observed that a mix of 75%
RCA and 25% Natural Aggregates has good mechanical properties. RCA with rough
surface allows better bonding with cement mix. Naik.et.al. (2006), this paper throws
some light on the production of recycled aggregates, their properties and their
suitability in the production of concrete. Also, the properties and the application of
recycled aggregate concrete are discussed in detail along with bringing out the
limitations of recycled aggregate concrete. This study showed that recycled aggregates
had higher water absorption value than natural aggregates but less density and strength.
Choudary.et.al. (2006), the author investigated workability and strength properties of
International Journal of Pure and Applied Mathematics Special Issue
3242
RCA. The recycled aggregate concrete is made by mixing 60% of recycled aggregates
with 40% of crushed stone chips. The aggregates used for concrete batching are
maintained at saturated surface dry condition. The workability of the recycled
aggregate concrete is slightly lower than that of the conventional concrete. The
compressive strength of the recycled aggregate concrete is slightly lower than that of
the conventional concrete and recycled concrete aggregate or recycled with
conventional concrete can be used in normal plain and reinforced concrete
construction. The recycled and conventional concrete containing 60% of recycled
aggregate and 40% of crushed natural stone chips occupies almost an intermediate
position is terms of workability and strength consideration between the others types of
concrete. So from economy and performance point of view, this type of concrete is
suitable only next to conventional concrete. Osei.et.al. (2013), in this study, the
compressive strength properties of concrete were investigated by completely replacing
Natural Aggregate (NA) with recycled concrete aggregate (RCA). Densities of both
RCA concrete and NA concrete were within the range of normal weight concrete. Both
RCA concrete and NA concrete showed the similar trends in the variation of strength
and density with time. Reduction in the 28-day compressive strength of concrete due to
complete replacement of natural aggregates with recycled concrete aggregate ranges
from 11% to 33%. RCA can replace NA in the production of both non-structural and
structural concrete. Patil.et.al. (2013), this study aimed to evaluate physical properties
of concrete using recycled coarse aggregate. In this research, concrete waste from
demolished structure has been collected and coarse aggregate of different percentages
is used for preparing fresh concrete (0%, 25%, 50%, 75% & 100%). The compressive
strength of recycled coarse aggregate (RCA) is found to be higher than the
compressive strength of normal concrete when used upto a certain percentage.
Recycled aggregate concrete is in close proximity to normal concrete in terms of split
tensile strength. The slump of recycled aggregate concrete is more than the normal
concrete. At the end, it can be said that the RCA upto 50 % can be used for obtaining
good quality concrete.
MATERIALS
International Journal of Pure and Applied Mathematics Special Issue
3243
Concrete is a composite material composed of water, coarse granular material (fine and
coarse aggregate) embedded in a hard matrix (cement or binder) that fills the space
among the aggregate particles and glues them together.
AGGREGATES: Aggregates used in concrete are divided into three categories:
Fine Aggregates: These aggregates passes through 4.75 mm I.S. sieve and retained on 150
micron. Coarse sand, it contains 90% of particles of size greater than 0.6 mm and less
than 2 mm .Medium sand, it contains 90% of particles size greater than 0.2 mm and less
than 0.6 mm, Fine sand, it contains 90% of particles of size greater than 0.06 mm and less
than 0.2 mm. Proper selection of sand is critical in the durability and performance of
concrete mixture
Coarse Aggregates: These aggregates passes through 63 mm I.S. sieve and retained on
4.75 micron. Coarse aggregates are particles greater than 4.75 mm, but generally range
between 9.5 mm to 37.5 mm in diameter. They can either be from Primary, Secondary or
Recycled sources.
Mixed Aggregate: Mixed aggregate is sometimes used for unimportant work without
separating into different sizes.
CEMENT: Another important material in concrete manufacture is cement. Cement is a
fine ground material consisting of compound of lime, silica, alumina and iron.
Discussions: The specific gravity of aggregates normally used in road construction ranges
from about 2.5 to 3.0 with an average of about 2.68. Though high specific gravity is
considered as an indication of high strength, it is not possible to judge the suitability of a
sample road aggregate without finding the mechanical properties such as aggregate
crushing, impact and abrasion values. Water absorption shall not be more than 0.6 per unit
by weight. From the above experiment, it is found that the specific gravity of RCA is
smaller than that of normal aggregate. Hence, RCA can be said to have less density than
normal aggregate and hence RCA is lighter. And also, it is found that water absorption is
higher in RCA than that of normal aggregates.
Fine Aggregates observations and Results
Determination of Moisture Content of Fine Aggregates by Pycnometer Method
International Journal of Pure and Applied Mathematics Special Issue
3244
Observations and Results: Trial No.
Sl. No. Observations and Calculations 1 2
1 Mass of empty pycnometer (M1 g) 684 g 654 g
2 Mass of pycnometer + fine aggregates (M2 g) 1184 g 1185 g
3 Mass of pycnometer + fine aggregates, filled with water (M3 g) 1869 g 1871 g
4 Mass of pycnometer filled with water only (M4 g)
Specific Gravity of Sand, G
5 Mass of fine aggregates, (M2 – M1)g 500 g 500 g
6 M3 – M4 328 g
7 (G – 1) / G 0.67
8 Moisture Content,
w = [(((M2-M1)/(M3-M4))((G-1)/G))-1] x 100 1.28 % 1.28 %
9 Average Moisture Content, wavg 1.28
Discussion: For fine aggregate, it is important to determine its moisture content because if
its water content is high, there will be an excess amount of water in the mixture. The
water-cement ratio used in the mixture is 0.5 and if the fine aggregates contain a certain
amount of water, this will have a considerable impact on the mixture and this may lead to
bleeding of concrete afterwards. Therefore, there is a need to ensure that the fine aggregate
is dry or if it is not the case, then the water content of the fine aggregates needs to be
reduced.
Coarse Aggregates - Oven Dry Method: Observations and Graph:
Table : Sieve Analysis of Fine Aggregates
Observations
and Results:
Conventional Recycled
Concrete
Aggregates Aggregates
Original
sample weight
(M1 g) 880 g 780 g
Oven dried
sample weight
(M2 g)
874 g 754 g
Moisture
content, w =
[(M1-M2) /
M2] × 100%
0.68% 3.44%
Table : Determination of Moisture
Content of Coarse Aggregates by Oven
Dry Method
Sieve
Size(mm)
Weight
Retained (Kg)
Percentage
Retained (%)
Cumulative
%
Retained
Cumulative
% Passing
4.75 0 0 0 0
2.36 0.014 1.4 1.4 98.6
1 0.302 30.2 31.6 68.4
0.0006 0.24 24 55.6 44.4
0.0003 0.354 35.4 91 9
0.00015 0.062 6.2 97.2 2.8
Pan 0.028 2.8 100 N/A
TOTAL 376.8
International Journal of Pure and Applied Mathematics Special Issue
3245
Graph 4.1: Particle Size Distribution Curve for Fine
Aggregates
Results: Effective size, in microns (D10,
sieve opening corresponding to 10% finer in
the graph) = 245 Microns. Uniformity
coefficient [(D60 / D10), D to be obtained
from the graph] = 310. Fineness modulus
(Sum of cumulative % weight retained / 100)
= 3.77
Discussion: According to IS 383 - 1970,
the fine aggregates belong to Zone II.
Table : Results for Effective Size, Uniformity
Coefficient and Fineness Modulus of Conventional and
Recycled Concrete Aggregates
Results:
Conventional
Recycled
Concrete
Aggregates Aggregates
Effective Size (D10) 7.6 mm 5.1 mm
Uniformity Coefficient
(D60/D10) 1.84 2.51
Fineness Modulus 2.78 2.53
Discussion: The D refers to the size or
apparent diameter of the soil particles while
the subscript (10, 30 and 60) denotes the
percent that is smaller than that diameter, e.g.
D10 = 0.16 mm means that 10% of the
sample grains have diameter smaller than
0.16 mm. A large value of Cu indicates that
the D10 and D60 sizes differ appreciably.
SHAPE TESTS: SHAPE TESTS: Flakiness Index and Elongation Index of Coarse
Aggregates
International Journal of Pure and Applied Mathematics Special Issue
3246
Table 4.1: Determination of Specific Gravity and Water Absorption of Coarse
Aggregates
Conventional Coarse Aggregates
Size of aggregates Weight of Thickness Weight of Length Weight of
Passing Retained Fraction gauge size, aggregates gauge Aggregates
through on IS Consisting mm in each size, in each
IS Sieve, Sieve, of at least Fraction mm Fraction
mm mm 200 pieces,
g
Thickness
gauge, mm passing
On length
gauge, mm
1 2
63 50
1 2 3 4 5 6 7
50 40 0 23.90 0 - -
40 31.5 0 19.50 0 58.00 0
31.5 25 0 16.95 0 - -
25 20 0 13.50 0 40.5 0
20 16 2000 10.80 550 32.4 220
16 12.5 850 8.55 69 25.5 175
12.5 10 500 6.75 150 20.2 98
10 6.6 110 4.89 22 14.7 0
TOTAL 3457 791 493
International Journal of Pure and Applied Mathematics Special Issue
3247
Table 4.9: Determination of Flakiness Index and Elongation Index of Conventional
Coarse Aggregates
Recycled Concrete Aggregates
Size of aggregates Weight of Thickness Weight of Length Weight of
Passing Retained Fraction gauge aggregates gauge aggregates
through on IS Consisting size, mm in each size, in each
IS
Sieve, Sieve, of at least - fraction mm fraction
Mm Mm 200 pieces,
g
- Passing
gauge, mm
- Retained on
gauge, mm
1 2 3 4 5 6 7
63 50 0 23.90 0 - -
50 40 0 27.00 0 81.00 0
40 31.5 0 19.50 0 58.00 0
31.5 25 0 16.95 0 - -
25 20 0 13.5 0 40.50 0
20 16 1540 10.80 26 32.4 72
16 12.5 920 8.55 16 25.5 159
12.5 10 420 6.75 11 20.2 85
10 6.3 400 4.89 0 14.7 113
TOTAL W=3280 X=53 Y=429
Table : Determination of Moisture Content of Fine Aggregates by Pycnometer Method
Discussion: For fine aggregate, it is important to determine its moisture content because if
its water content is high, there will be an excess amount of water in the mixture. The
water-cement ratio used in the mixture is 0.5 and if the fine aggregates contain a certain
amount of water, this will have a considerable impact on the mixture and this may lead to
bleeding of concrete afterwards. Therefore, there is a need to ensure that the fine aggregate
is dry or if it is not the case, then the water content of the fine aggregates needs to be
reduced.
Coarse Aggregates - Oven Dry Method:
International Journal of Pure and Applied Mathematics Special Issue
3248
Table 4.4: Determination of Moisture Content of
Coarse Aggregates by Oven Dry Method
Observations and Results:
Conventional
Recycled
Concrete
Aggregates Aggregates
Original sample weight (M1
g) 880 g 780 g
Oven dried sample weight
(M2 g) 874g 754g
Moisture content, 874 g 754 g
w = [(M1-M2) / M2] × 100% 0.68% 3.44%
Discussion: From the above results, it is
found that RCA contains more water than that
of conventional aggregates because RCA has
a higher amount of cement and thus absorbs
more water than normal aggregates due to
larger pore sizes and hence, there is a need to
encounter for water absorption. Due to this,
RCA will absorb the water during mixing of
concrete and this will lead to a bad mixture as
there will be a lack of water and thus there
will be a need to add more and more water.
Fine Aggregates:
Observations and Graph:
Sieve Size Weight Percentage Cumulative
%
Cumulative
%
(mm) Retained
(Kg)
Retained
(%) Retained Passing
4.75 0 0 0 100
2.36 0.014 1.4 1.4 98.6
1 0.302 30.2 31.6 68.4
0.0006 0.24 24 55.6 44.4
0.0003 0.354 35.4 91 9
0.00015 0.062 6.2 97.2 2.8
Pan 0.028 2.8 100 N/A
TOTAL 376.8
Table : Sieve Analysis of Fine Aggregates
Graph : Particle Size Distribution Curve for Fine
Aggregates
Results: Effective size, in microns (D10, sieve opening corresponding to 10% finer in the
graph) = 245 Microns. Uniformity coefficient [(D60 / D10), D to be obtained from the
graph] = 310. Fineness modulus (Sum of cumulative % weight retained / 100) = 3.77
Discussion: According to IS 383 - 1970, the fine aggregates belong to Zone II.
International Journal of Pure and Applied Mathematics Special Issue
3249
Graph : Particle Size Distribution Curve for Conventional Aggregates And Recycled Concrete
Aggregates
Discussion: The D refers to the size or apparent diameter of the soil particles while the
subscript (10, 30 and 60) denotes the percent that is smaller than that diameter, e.g. D10 =
0.16 mm means that 10% of the sample grains have diameter smaller than 0.16 mm. A
large value of Cu indicates that the D10 and D60 sizes differ appreciably.
Table 4.1: Determination of Specific Gravity and Water Absorption of Coarse Aggregates
Conventional Coarse Aggregates
Size of aggregates
Weight of Thickness Weight of Length Weight of
fraction gauge size, mm aggregates gauge aggregates
Passing Retained
through on IS consisting mm in each size, in each
Results:
Conventional
Recycled
Concrete
Aggregates Aggregates
Effective Size (D10) 7.6 mm 5.1 mm
Uniformity Coefficient
(D60/D10) 1.84 2.51
Fineness Modulus 2.78 2.53
Table : Results for Effective Size, Uniformity
Coefficient and Fineness Modulus of
Conventional and Recycled Concrete Aggregates
Coarse Aggregates, Observations and Graph:
Sieve Analysis on Conventional Coarse Aggregates
Sieve
Size Weight Percentage
Cumulative
%
Cumulative
%
(mm) Retained
(Kg)
Retained
(%)
Retained Passing
40 0 0 0 100
20 0 0 0 100
10 1.56 78 78 22
4.75 0.44 22 100 0
Pan 0 0 100 N/A
Table : Sieve Analysis on Conventional Coarse Aggregates
Sieve Analysis on Recycled Concrete Aggregates
Sieve
Size Weight Percentage
Cumulative
% Cumulative %
(mm)
Retained
(Kg) Retained
(%) Retained Passing
40 0 0 0 100
20 0 0 0 100
10 1.2 60 60 40
4.75 0.66 33 93 7
Pan 0.14 7 100 N/A
TOTAL 253
International Journal of Pure and Applied Mathematics Special Issue
3250
IS Sieve, mm Sieve, mm of at least 200 pieces, -
Fraction passing
thickness gauge,
mm mm
Fraction retained
on length gauge,
mm
1
2 3 4 5 6 7 63 50 0 23.90 0 - -
50 40 0 27.00 0 81.00 0
40 31.5 0 19.50 0 58.00 0
31.5 25 0 16.95 0 - -
25 20 0 13.50 0 40.5 0
20 16 2000 10.80 550 32.4 220
16 12.5 850 8.55 69 25.5 175
12.5 10 500 6.75 150 20.2 98
10 6.3 110 4.89 22 14.7 0
TOTAL 3457 - 791 - 493
Table : Determination of Flakiness Index and Elongation Index of Conventional Coarse Aggregates Recycled Concrete Aggregates
Size of aggregates Weight of Thickness Weight of Length Weight of
Passing Retained fraction gauge aggregates gauge Aggregates
through on IS consisting size, mm in each size, mm in each
IS Sieve, mm Sieve, mm of at least200 pieces, g -
Fraction passing
thickness gauge, mm
fraction retained on
length gauge, mm
1 2 3 4 5 6 7
63 50 0 23.90 0 - -
50 40 0 27.00 0 81.00 0
40 31.5 0 19.50 0 58.00 0
31.5 25 0 16.95 0 - -
25 20 0 13.50 0 40.5 0
20 16 1540 10.80 26 32.4 72
16 12.5 920 8.55 16 25.5 159
12.5 10 420 6075 11 20.22 85
10 6.3 400 4.89 0 14.7 113
TOTAL W = 3280 - X = 53 - Y = 429
International Journal of Pure and Applied Mathematics Special Issue
3251
Table 4.10: Determination of Flakiness Index and Elongation Index of
Recycled Concrete Aggregates
Results:
Conventional
Recycled
Concrete
Aggregates Aggregates
Flakiness Index = [(X1+ X2+…..) / (W1 + W2
+….)] × 100 22.88% 1.62%
Elongation Index = [(Y1 + Y2 +…) / (W1 + W2
+….)] × 100 14.26% 13.10%
Discussions: Flaky and elongated
particles should be avoided in
pavement construction, particularly
in surface course. If such particles
are present in appreciable
proportions, the strength of
pavement layer would be adversely
affected due to possibility of
breaking under loads. Workability is
reduced for cement concrete. As per
IRC recommendations, the
conventional aggregates tested
proved to be within permissible
limits for use in all types of
pavements except for bituminous
macadam and WBM base course
and surface course ones. The
recycled concrete aggregates are
within limits for all types of
pavements and may be used for
anyone based on its flakiness index.
Results for Flakiness Index and Elongation Index of
Conventional and Recycled Concrete Aggregates
Angularity Number
Observations and Results : Conventional
Recycled
Concrete
Aggregates Aggregates
W = Mean weight of
aggregates in the cylinder, g 4310 g 4225 g
C = Weight of water required
to fill the cylinder, g 3000 g 3000 g
G = Specific gravity of aggregate 2.73 2.46
Angularity number = 67-100
W/CG 14 10
Discussion: From the values obtained
above, it is found that the angularity number
of conventional aggregates is higher than
that of RCA. Thus, higher the angularity
number, more angular and less workable is
the aggregate mix.In cement concrete mix,
rounded aggregates may be preferred
because of better workability, lesser specific
surface and higher strength for particular
cement content. In addition, the more
angular shape of the RCA and its rougher
surface texture are also what contribute
AGGREGATE IMPACT TEST
International Journal of Pure and Applied Mathematics Special Issue
3252
Table : Determination of Aggregate Impact Value for Conventional
and Recycled Concrete Aggregates
Results:
Conventional
Recycled
Concrete
Aggregates Aggregates
Original weight of aggregates, W1 g 320 g 300 g
Weight of fraction passing
through 2.36mm IS sieve, W2 g 100 g 100 g
Aggregate Impact Value = (W2 / W1) ×
100% 31.30% 33.30%
Discussion:10% →
Exceptionally strong.10–20%
→ Strong.20–30% →
Satisfactory for road surfacing. >
35% → Weak for road surfacing.
STANDARD CONSISTENCY OF CEMENT
Portland
Cement
(OPC)
Slag
Cement
(PSC)
Weight of empty dry bottle,
W1 g 66.3 g 80.3 g
Weight of empty bottle +
water, W2 g 176.9 g 178.8 g
Weight of empty bottle +
kerosene, W3 g 153.4 g 157.6 g
Weight of cement, W4 g 57.6 g 49.3 g
Weight of bottle + cement +
kerosene, W5 g 196.5 g
193.9 g
Specific gravity of kerosene,
‘g’ 0.79
0.79
Specific gravity of cement,
G = {W4 (W3-W1)} /
{(W4+W3-W5)(W2-W1)}
3.15 3.00
Table: Determination of Specific Gravity of Cement
SPECIFIC GRAVITY OF A CEMENT
Discussion :
The specific gravity of Ordinary Portland
Cement (OPC) varies from 3.1 to 3.15
and that of Portland Blast Furnace Slag
Cement varies from 3.0 to 3.05.
International Journal of Pure and Applied Mathematics Special Issue
3253
Observations and Results:
Ordinary Portland Portland Slag
Cement (OPC) Cement (PSC)
Weight of cement
taken (W1 g) 400 g 400 g
Quantity of water
added to cement
(W2 ml)
150 ml 116 ml
Depth of penetration
(mm) 5 mm 8 mm
Normal Consistency =
(W2/W1) X 100 % 37.5 % 29.0 %
Table : Determination of Normal Consistency of Cement
Discussion:
The basic aim is to find out the water
content required to produce a cement
paste of standard consistency as
specified by the IS: 4031 (Part 4) –
1988. From the above results, normal
consistency of OPC is more than that
of PSC. It is seen that more water is
required to produce a cement paste in
OPC and hence OPC requires more
water to be able to produce a reliable
cement paste whereas with lesser
amount of water in PSC, depth of
penetration is more and thus, more
workable is the paste.
INITIAL AND FINAL SETTING TIME OF CEMENT
Results :
Ordinary Portland
Cement Portland Slag Cement
(OPC) (PSC)
Initial Setting
Time 156 mins 160 mins
Final Setting
Time 194 mins 215 mins
Discussion: From the above values,
OPC takes lesser time than PSC to
set. Hence, once the mixing is done,
the concrete has to be used quickly
compared to PSC which takes more
time to set.
METHODOLOGY
SOURCES OF MATERIALS
Different materials were obtained from different sources and the laboratory tests were
performed. The recycled aggregates were obtained from a demolished house which was
about 30 years old. The concrete used in Mauritius is usually M20 grade one. The slab,
columns and beams of the demolished building were made of this grade of concrete and
the walls were made of concrete hollow blocks.
International Journal of Pure and Applied Mathematics Special Issue
3254
SCHEDULE OF WORK
The time plan prepared for casting of concrete and also for testing of the concrete cubes
and cylinders after acquiring all the required materials is as shown below
Monday Tuesday Wednesday Thursday Friday Saturday Sunday
17-Mar 18-Mar 19-Mar 3/27/2014 -
75%
3/28/2014
- 0%
22-Mar 23-Mar
3/24/2014 3/25/2014 /26/2014 - 50% 3/29/2014
4 - 100% RPC
(OPC)
25% RCA RCA (OPC) RCA (OPC) RPC (OPC) RPC (OPC) 30-Mar
4/1/2014 4/2/2014 - 50%
RCA (PSC) +
4/3/2014 - 25%
RCA (PSC)
+
4/4/2014 - 75%
RCA
(PSC) +
4/5/2014 - TEST 0%
RCA
6-Apr
31-Mar
(PSC) + TEST
4/9/2014 - TEST
TEST 50% TEST 75% (PSC) -
100% RCA OPC) RCA (OPC RCA (OPC)
7-Apr 8-Apr 100% RCA
(PSC)
TEST 50%
RCA (PSC)
TEST 25%
RCA (PSC)
TEST 75%
RCA (PSC) 13-Apr
14-Apr 15-Apr 16-Apr 17-Apr 18-Apr 4/19/2014 TEST 0%
OPC
20-Apr
21-Apr
4/22/2014 –
TEST
100% RCA
(OPC)
4/23/2014 – TEST
25% RCA
(OPC)
4/24/2014 –
TEST 50%
RCA (OPC)
4/25/2014 –
TEST 865
% RCA (OPC)
TEST 0%
RCA (PSC) 27-Apr
28-Apr 29-Apr
4/30/2014 –
TEST 100% RCA (PSC)
5/01/2014 –
TEST 50% RCA (PSC)
5/02/2014 –
TEST 25%
RCA (PSC)
5/03/2014 –
TEST 75% RCA (PSC)
4-May
International Journal of Pure and Applied Mathematics Special Issue
3255
- Casting of Concrete
- 7th
Day Test on Cubes and Cylinders
- 28th
Day Test on Cubes and Cylinders
Table 5.1: Work Schedule
MIX DESIGN AND CALCULATIONS
For each mix specimen, the quantity of materials required for concrete mixing has been
calculated and tabulated. The water/cement ratio is kept constant but however, the water
content may vary for the slag cement due to its property to improve workability. For each
mix specimen, the following are to be cast for the basic tests:
6 cubes for compressive strength test - 3 at the age of 7 days
- 3 at the age of 28 days
6 cylinders for compressive strength test
- 3 at the age of 7 days
- 3 at the age of 28 days
International Journal of Pure and Applied Mathematics Special Issue
3256
6
cylinder
s for
split-
tensile
strength
test
- 3 at the age of 7 days
- 3 at the age of 28 days
Quantity of Materials
Type of
Cement Ratio
Mix Specimen Cement
(kg)
Water
(L)
Fine
Aggregates
(kg)
Coarse Aggregates (kg)
W/C
Ratio RCA
Conventio
nal
Mix1 0% RCA 38.2 19.1 76.4 0 112.6 0.5
Ordinary Mix 2 25% RCA 38.2 19.1 76.4 28.1 84.4 0.5
Portland Mix 3 50% RCA 38.2 19.1 76.4 56.3 56.3 0.5
Cement
(OPC) Mix 4 75% RCA 38.2 19.1 76.4 84.4 28.1 0.5
Cement Mix 5 100% RCA 38.2 19.1 76.4 112.6 0 0.5
(OPC) Mix 6 0% RCA 38.2 19.1 76.4 0 112.6 0.5
Portland Mix 7 25% RCA 38.2 19.1 76.4 28.1 84.4 0.5
Slag Mix 8 50% RCA 38.2 19.1 76.4 56.3 56.3 0.5
Cement Mix 9 75% RCA 38.2 19.1 76.4 84.4 28.1 0.5
(PSC) Mix 10 100%RCA 38.2 19.1 76.4 112.6 0 0.5
Total for 6 cubes
and 12 OPC 191 95.5 382 281.4 281.4
Cylinders PSC 191 95.5 382 281.4 281.4
Table : Determination of Slump Values of Concrete using OPC and PSC
International Journal of Pure and Applied Mathematics Special Issue
3257
Table : Quantity of Materials Required Slump Values for Concrete
with Water Cement Ratio = 0.5
0 %
RCA
25 %
RCA 50 % RCA
75 %
RCA 100 % RCA
Using OPC 100 mm 110 mm 115 mm 110 mm 110 mm
Using PSC 100 mm 100 mm 90 mm 115 mm 100 mm
Discussion: The standard slump values for normal RCC work
ranges from 80-150 mm. If the concrete mixture is too wet, it
will have a greater slump and the coarse aggregates will settle at
the bottom of concrete mass, i.e. it will collapse and as a result
concrete becomes a non-uniform composition. If the concrete
mixture is too dry, it will have a lesser slump value
Results: Compaction Factor for Concrete with Water
Cement Ratio = 0.5 Using OPC
0 % 25 %
50
%
75
%
100
%
RCA RCA RCA RCA RCA
Weight of empty
cylinder (W,g) 11,980 g 11,980 g 11,980g 11,980 g 11,980 g
Weight of cylinder
with
partially compacted
concrete
(W1g)
23,180 g 23,320 g 23,420g 23,160 g 23,200 g
Weight of cylinder
with fully compacted
concrete (W2 g)
24,520 g 24,140 g 23,960g 23,900 g 24,110 g
Compaction Factor
= (W1-W / W2-W) 0.89 0.93 0.95 0.93 0.92
Compaction Factor for Concrete with Water Cement
Ratio= 0.5 Using PSC
0 % 25 %
50
%
75
% 100 %
RCA RCA RCA RCA RCA
Weight of empty
cylinder (W,g) 11,980 g 11,980 g 11,980g 11,980 g 11,980 g
Weight of cylinder
with
partially compacted
concrete
(W1g)
23,440 g 23,480 g 22,700 g 23,480 g 22,660 g
Weight of cylinder
with fully
compacted concrete
(W2 g)
24,700g 24,460g 24,260g 24,160g 23,780g
Compaction Factor
= (W1-W / W2-W) 0.9 0.92 0.87 0.94 0.91
Discussion: Following is a table showing the standard limits
for compaction factor of concrete: Table : Standard Values for Compaction Factor
Degree of
workability
Compacting factor
Small
apparatus
Large
apparatus
Very low 0.78 0.80
Low 0.85 0.87
Medium 0.92 0.935
High 0.95 0.96
Very high - -
Vee-Bee Degrees for Concrete with Water Cement Ratio = 0.5
Table : Determination of Vee-Bee Degrees for Concrete with
Different Percentage of RCA using OPC and PSC
0 % 25 % 50 % 75 % 100 %
RCA RCA RCA RCA RCA Using 9.3 7.1 6.8 7.2 7.0
OPC VB-
degrees
VB degrees VB Degrees
Using 9.1 9.5 11.3 6.9 8.9
PSC VB-
degrees
VB-
degrees
VB-
degrees
VB-
degrees
VB-degrees
Discussion:Following is a table showing the standard limits of Vee-Bee test on concrete:
Workability description Vee-Bee time, in seconds
Extremely dry 32-18
Very stiff 18-10
Stiff 10-5
Stiff plastic 5-3
Plastic 3-0
Flowing -
Table : Standard limits for Vee - Bee test on concrete
RESULTS AND DISCUSSIONS In this chapter, the results obtained by performing tests on hardened concrete
are displayed and explained. These tests have been explained in detail in . Firstly, compressive strength tests were
performed on concrete cubes and cylinders after 7 and 28 days of curing. Secondly, split tensile strength test was
performed on concrete cylinders at 7 and 28 days of curing as well. The tests were done on concrete with RCA
proportions using both Ordinary Portland Cement (OPC) and Portland Slag Cement (PSC).
International Journal of Pure and Applied Mathematics Special Issue
3258
International Journal of Pure and Applied Mathematics Special Issue
3259
ACKNOWLEDGMENT
This Research work was supported by DST FIST(No: SR/FST/ETT-378/2014,Dated 24/11/2015) in SET-JU. We
are thankful to our organization that provided expertise that greatly assisted the research
Reference
1. Concrete - Wikipedia, http://en.wikepedia.org/wiki/concrete.
2. Stress - Strain Behaviour of Concrete, http://www.theconcreteportal.com/cons_rel.html.
3. Waste Management at the Construction Site, http://www.intechopen.com/books/integrated-waste-
management-volume-i/wastemanagement-at-the-construction-site
4. Cement Concrete and Aggregates Australia, Uses of Recycled Aggregates in Construction, May 2008.
5. Recycled Aggregates, http://www.cement.org/for-concrete-books-learning/concretetechnology/concrete-
design-production/recycled-aggregates
6. Concrete Recycling- Wikipedia, http://en.wikepedia.org/wiki/concrete-recycling.
7. M.S. Shetty, “Concrete Technology: Theory And Practice”, S. Chand & Company Ltd., 2009
8. Sowmya T, Srikanth. M. Naik, Dr. B. V. Venkatasubramanya., Application of Recycled Aggregates in
Construction, 2000.
9. Ammon Katz., Properties of Concrete Made with Recycled Aggregate from Partially Hydrated Old Concrete,
October 2002, Cement and concrete research 33 (2003), pp 703-711.
10. Shailendrakumar, Dr. A. K. Choudhary, Dr. B. P. Verma., Prediction of Splitting Tensile Strength of Recycled
Aggregate Concrete, 2004.
11. K V Chaurpagar., Study of Polymer Modified Recycled Aggregate Concrete with Steel Fibers, 2004.
International Journal of Pure and Applied Mathematics Special Issue
3260
12. M C Limbachiya, a Kolouris, J J Roberts and A N Fried., Performance of Recycled Aggregate Concrete, 2004.
13. Dr S.C. Natesan, C Lavana Kumar and Chandra Mohan M P., Strength Properties of Concrete Using
Demolished Waste as Partial Replacement Coarse Aggregate, 2005.
14. Rohini R Naik, M. Manjunath, Dr. K. B. Prakash., Stability of Recycled Aggregate in Construction, 2006.
15. S. S. Choudhary, J. P. Nayak., Structural Behaviour of Concrete, 2006.
16. Daniel Yaw Osei., Compressive Strength of Concrete Using Recycled Concrete Aggregate as Complete
Replacement of Natural Aggregate, October 2013, Volume 2, No.10.
17. Sudhir P. Patil, Ganesh S. Ingle, Prashant D. Sathe., Recycled Coarse Aggregates, 2013.
18. Hubert Chang, Ryan Morgan, Umet Aziz, Simon Herfellner, Kenneth Ho., Performance and Implementation
of Low Quality Recycled Concrete Aggregate, 2013, Vol 10, Iss 1, Pp 74-84.
19. IS 383:1970, “Specification for Coarse and Fine Aggregates from Natural Sources for Concrete”, 2nd Revision.
20. IS 455:1989, “Specification for Portland slag cement”, 4th Revision.
International Journal of Pure and Applied Mathematics Special Issue
3261
SHAPE TESTS:
International Journal of Pure and Applied Mathematics Special Issue
3262
3263
3264
top related