Effect of Recycled Coarse Aggregates in Concrete

Prepared by
Nirmal Krishnan A K

INTRODUCTION
 Concrete
 World’s second most consumed material.
 Basic need for urban development.
 Out of all construction materials concrete is the main constituent.
 It is estimated that 25 billion tonnes of concrete is manufactured each year.
 Ingredients
 Cement
 Aggregate
 Water
 Admixtures

INTRODUCTION (contd.)
 Construction and demolition waste
 Demolition waste
 Construction waste
 Road work waste
 Other construction waste
 Environmental problems
 Scarcity of landfills
 Non biodegradable
 Solution
 RECYCLE
 REUSE

RECYCLING OF CONCRETE
 BENEFITS
 Saves landfill space
 Use as gravel reduces need for gravel mining
 Use as base material for roadways reduce the pollution involved in
trucking material
 Recycling of 1 ton of concrete could save 1360 gallons of water, 900
Kg of CO2
 Rubblization

RECYCLED AGGREGATES
 Production of recycled aggregates
 Uses of recycled aggregates
 Types of recycled aggregates
 Recycled coarse aggregate(RCA)
 Recycled fine aggregate(RFA)

METHODS TO PRODUCE RECYCLED
AGGREGATES
 HEATING AND RUBBING METHOD
 ECCENTRIC-SHAFT ROTOR METHOD
 MECHANICAL GRINDING METHOD
 ELECTRIC PULSE POWER METHOD

LITERATURE REVIEW
Sl.no Author Year Work done
1 P.C Khergamwala et al 2013 Studied on recycled coarse aggregates from
fresh concrete waste
2 N. Sivakumar et al 2013 Study on recycled coarse aggregate made
from demolition waste
3 Mamery Sérifou et al 2014 Studied about the possibility of using fresh
concrete waste as recycled aggregates in
concrete
7

CASE STUDY
 CASE STUDY 1-EXPERIMENTAL STUDIES ON HIGH STRENGTH
CONCRETE BY USING RECYCLED COARSE AGGREGATE
 CASE STUDY 2-EFFECT OF RECYCLED COARSE AGGREGATES ON
CHARACTERISTIC STRENGTH OF DIFFERENT GRADES OF CONCRETE

CASE STUDY 1
 High strength concrete(HSC)
Concrete with characteristic compressive strength higher than
40MPa
Materials used
Cement
Water
Fine aggregate
Coarse aggregate
Mix design
1:1.97:3.35
wc ratio 0.4

Mix
 HSC
 0% recycled coarse aggregates
 50% recycled coarse aggregates with reduced w/c ratio

TEST ON HSC
TEST ON FOR DURABILITY
HSC
 Acid resistance test
 Saturated water absorption
test
 Porosity test
TEST FOR STRENGTH ON
HSC
 Slump test
 Compression test
 Indirect tensile test
 Modulus of elasticity

SLUMP TEST
 Slump cone or Abrams cone
 Filling and tamping of mix
 Removal of cone
 Measurement of slump
 Result
Fig.1 Graph showing the result of slump test
(Source: N.Sivakumar et al, 2014)

COMPRESSION TEST
 Compression testing machine
 Specimen 150mm CUBE
 After 24 hours immerse in water for curing
 Strength after 7 and 28 day curing
 Load till failure
 Compressive strength is the ratio between load at failure to cross
sectional area

Fig.3 Variation of compressive strength after 28 days
Fig.2 Variation of compressive strength after 7 days

Fig.4 Graph showing percentage of Compressive Strength remained

INDIRECT TENSILE TEST
 Cylinder of size 300mm AND 150mm diameter
 After 24 hours immerse in water for curing
 Strength after7 and 28 day curing
 Loading as specified in figure
 Load till failure
Fig.5 schematic representation of indirect tensile test

Fig.6 Variation of Tensile strength after 7
days (Source: N.Sivakumar et al, 2014)
Fig.7 Variation of Tensile strength after 28 days

Fig.8 Graph showing percentage of Tensile Strength remained

MODULUS OF ELASTICITY TEST
 Specimen 152mm diameter and 312mm long cylinder
 Fix the specimen in the compressometer and place it in compression testing
machine
 Measure the average deformation of two diametrically opposite locations to
the nearest 5 millionths of strain
 The modulus of elasticity is calculated
 Obtain a stress-strain curve

Fig.9 Stress and Strain Relationship for 0%
RCA replacement(Source: N.Sivakumar et al,
2014)
Fig.10 Stress and Strain Relationship for 50%
RCA replacement (Source: N.Sivakumar et al,
2014)

Fig.11 Graph showing variation of modulus of elasticity

ACID RESISTANCE TEST
 Specimen 150mm cubes
 Weighed
 Immersed in 3% Sulphuric acid for 45 days
 Surface dried and weighed
 The percentage loss in weight and the percentage loss in compressive strengths
are calculated

Table.1 Reduction in Compressive Strength based on Acid resistance Test
Percentage replaced
28 day compressive
strength (MPa)
After 45 days immersion of cubes in Sulphuric acid solution
Percentage reduction
in weight
Compressive strength (MPa)
Percentage reduction in
compressive strength compared
to 28 day strength
0 42.1 0.42 38.3 9.03
10 38.2 0.47 33.8 11.52
20 35.3 0.51 31.1 11.9
30 32.5 0.56 28 13.85
40 30 0.59 25 16.67
50 26.6 0.63 21.3 19.92
50 % with reduced water
content
37 0.52 32 12.33

SATURATED WATER ABSORPTION AND
POROSITY
 Procedure
SPECIMEN 100mm CUBES
After 24 hours immerse in water for curing
After 28 and 90 days of curing
Weighed and dried at 1050C
Continued till weight at consecutive days remains same
Cooled at room temperature and immersed in water
Continued till weight at consecutive days remains same

SATURATED WATER ABSORPTION AND
POROSITY (contd.)
 Saturated water absorption
Percentage water absorption =
(𝑊𝑠−𝑊𝑑)
𝑊𝑑
x 100
 Porosity
Effective porosity =
(Ws –Wd )
(𝑊𝑠−𝑊𝑠𝑢𝑏)
x 100

Table.2 Test for saturated water absorption & porosity
Percentage
replaced
Saturated
water
absorption
Percentage
increase in
saturated water
absorption
Effective
porosity
Percentage
increase in
Effective
porosity
0 1.10 0 3.30 0
10 1.24 12 3.51 6
20 1.38 25 3.85 16
30 1.56 41 3.90 18
40 1.66 50 3.97 20
50 1.74 57 4.05 22
50% with
reduced w/c
ratio
1.37 24 3.59 9

CASE STUDY 2
 Materials
 Cement :- OPC grade 43
 Fly ash :- the 45 micron passing fraction in the unprocessed fly ash
was more than 90 percent
 Fine aggregates :-specific gravity 2.61
 Coarse aggregates :-
 Natural aggregates specific gravity:2.7
 Recycled coarse aggregates made from laboratory waste and left over fresh
concrete specific gravity:2.45
 Water

MIX DESIGN
MIX
MIX
PROPORTION
FLY ASH%
CONSTITUTIONS (Kg/M3)
W/C RATIO
CEMENT SAND AGGREGATES
M20 1:1.5:3.4 25 400 600 1360 0.5
M30 1:1.25:2.75 25 450 562.5 1237.6 0.5
Table.3 Mix proportions for different mixes (Source: P.C
Khergamwala et al, 2013)

Mix
 M20 concrete
 25% recycled coarse aggregate
 75%recycled coarse aggregate
 M30 concrete

COMPRESSIVE STRENGTH TEST
 Cubes of size 150 mm are casted for all the mixes
 Immersed in water for curing
 Compressive strength at 7 day and 28 days of curing is fount out
using compression testing machine
 Compressive strength is the ratio between load at failure to cross
sectional area
 Percentage reduction in characteristic compressive strength is
calculated

Table.4 Compressive strength (N/mm2) of concrete mixes
(Source: P.C Khergamwala et al, 2013)
Recycled
aggregate
(%)
M20 Compressive
strength
%
Reduction in
fck
M30 Compressive
strength
%
Reduction
in fck
7 days 28days 7 days 28 days
0 18.2 25.9 - 23.5 34.2 -
25 17.4 25.8 0.4 20.4 32.1 6.1
50 18.7 26.7 3% increase 21.9 33.3 2.6
75 12.4 18.6 28.2 17.2 26.7 21.9
100 16.4 21.3 17.8 21.2 29.8 12.9

Fig.12 Compressive strength of concrete at 7
days(Source: P.C Khergamwala et al, 2013)
Fig.13 Compressive strength of concrete at
28 days (Source: P.C Khergamwala et al,
2013)

SUMMARY
 Specific gravity of RCA is lower and Water absorption of RCA is higher than
natural aggregate.
 The compressive strength of concrete containing 25% and 50% RCA is in close
proximity to that of normal concrete.
 For M 20 it was seen that compressive strength increased by 3 % with addition of
RCA but only up to 50%.
 When amount of RCA is increased above 50%, it adversely affects the
compressive strength of concrete.

CONCLUSIONS
 Recycled aggregates can be used as an alternative for natural aggregates.
 By using there recycled aggregates we can save our precious land from dumping
C&D wastes as landfills.
 In modern times broken brick, marble, plastic, etc. are used as aggregates.
 So these recycled aggregates can be used as fine aggregate as well as coarse
aggregates.

CONCLUSIONS (contd.)
 For HSC 30%-40% recycled coarse aggregates with reduced wc ratio may give
same output as normal concrete gives.
 For low grade concrete 50% RCA replacement will give almost equal results as
normal concrete gives.
 Problem in recycled aggregate concrete is that due to the low wc ratio the
workability will be very low
 Due to high water absorption rate of recycled aggregates the water content in the
mix should monitored carefully

REFERENCES
 Pinal C. Khergamwala, Dr. Jagbir Singh, Dr. Rajesh Kumar International 6,
“Effect of Recycled Coarse Aggregates on Characteristic Strength of Different
Grades of Concrete” Journal of Civil Engineering and Technology, volume 4.
 N.Sivakumar, S.Muthukumar, V.Sivakumar D.Gowtham, V.Muthuraj
“Experimental Studies on High Strength Concrete by Using Recycled Coarse
Aggregate” International Journal of Engineering and Science, vol.4, issue 01.
 Mamery Sérifou, Z. M. Sbarta, S. Yotte, M. O. Boffoué,2 E. Emeruwa, and F.
Bos “A Study of Concrete Made with Fine and Coarse Aggregates Recycled from
Fresh Concrete Waste” Journal of Construction Engineering Volume 2013,
Article ID 317182.
 S. K. Singh, and P. C. Sharma (2007) “Use of Recycled Aggregates in Concrete-
A Paradigm Shift”
 http://www.buildingresearch.com.np

Effect of Recycled Coarse Aggregates in Concrete

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