AN INVESTIGATION ON PROCESSING AND PROPERTIES OF
RECYCLED AGGREGATE CONCRETE
Das A.1*, Alauddin M.2 & Hossain B.M.2
1 Asst. Professor, Department of Civil Engineering, Southern University Bangladesh (SUB),
Chittagong, <[email protected]> 2 Student, Department of Civil Engineering, Southern University Bangladesh (SUB), Chittagong,
<[email protected]> 3 Student, Department of Civil Engineering, Southern University Bangladesh (SUB), Chittagong,
ABSTRACT
A significant amount of natural resource can be saved if the demolished concrete is recycled for new
construction. In addition to the saving of natural resources, recycling of demolished concrete will also
provide other benefits, such as the creation of additional business opportunities, saving the cost of
disposal, saving money for local government and other purchasers’ etc. Recycled aggregate is
comprised of crushed, graded inorganic particles processed from the materials that have been used in
the constructions and demolition debris. The objective of this thesis is to achieve the target strength of
concrete by using recycled aggregate fully or partially with the natural fresh stone. Local sand (FM
value 1.83) is used as fine aggregate. In this investigation, demolished concrete blocks are collected
from demolished head of the Pile and broken into pieces as aggregates as per ASTM C33. In this study,
ACI 211-91 is used for mix design & conducted compressive strength test for 72 cubes (100mm x
100mm x 100mm) with different mix ratios.
The test Result has revealed that maximum 65%-84% of target strength can be achieved from recycled
aggregate.
Keywords: Recycle Aggregate; Fresh Aggregate; Concrete Compressive Strength; Slump test;
INTRODUCTION
The generation of huge amounts of construction waste is anticipated due to the demolition of older
structures such as power stations built more than 30 years ago. On the other hand, the reuse of
construction waste is highly essential from the viewpoint of Life Cycle Assessment (LCA) and
effective recycling of construction resources. In order to promote the reuse of construction waste, it is
necessary to achieve three basic concepts: (1) assurance of safety and quality, (2) decrease of
environmental impact, and (3) increase of cost effectiveness of construction. This paper outlines the
development of a recycling system, application of recycled aggregate concrete produced by the
aggregate replacing method, which is effective in reducing both cost and environmental impact from
the viewpoint of LCA for concrete waste generated by the demolition of large-scale buildings such as
powerhouses.
Global Construction industry growth is substantial in size. In a report of global insight, it is predicted
that construction expenditure has been increased about 1400 billion US dollar from the year 2008 to
2013. These figures indicate a tremendous growth in the construction sector almost one and a half times
in the coming 5 years. The construction industry Worldwide is a conspicuous consumer of the raw
material of many types and thus large material inventories are required to sustain the growth. Also
proportionately related are the issues of cost that is rising since material inventory is becoming scarce
and material has to be procured from distant places. Among the various raw materials used in
construction, aggregates are important components for all the construction activities and the demand in
2007 has seen an increase by five percent, to over 21 billion tones, the largest being in developing
1st International Conference on Research and Innovation in Civil Engineering (ICRICE 2018), 12 –13 January, 2018, Southern University Bangladesh (SUB), Chittagong, Bangladesh ISBN: 978-984-34-3576-7
countries like China, India, etc. Keun- Hyeok Yang has reported construction industry’s global
requirement of natural aggregate Around 8 - 10 billion tons annually after the year 2010. (1 p. 6)
METHODOLOGY (SECTIONS)
When recycled aggregate concrete is applied to buildings, road base etc., the quality required is generally equivalent to natural aggregates such as gravel and sand.
Experimental Methods
The overall experimental program consisted of two stages: 1) a comprehensive study of the properties
of new concrete made with recycled aggregate that is prepared by crushing partially hydrated old concrete; 2) a study of the effect of recycled fines only on the properties of new concrete. This paper presents the results of stage 1 of the study. Demolished concrete blocks are collected from the structural members of the demolished buildings. The collected concrete samples were have been broken into pieces mechanically in particular sizes as 5 mm to 20 mm FM of which is 4.20. The aggregates are tested for absorption capacity, specific gravity, moisture content, unit weight, and FM. The specific gravity and absorption capacity are determined as per ASTM C128, (2 p. 6) unit weight as per ASTM C29. The FM, water absorption and specific gravity of sand used in this investigation were 1.83, 3.95%, and 2.55, respectively. After investigation of aggregates, concrete cube specimen of size 100 mm x 100 mm x 100 mm in are made for evaluation of compressive strength at 7, 21, 28 and 60 days as per ASTM
C39. W/C ratios of recycled aggregate concrete are 0.65, 0.61 and 0.52. In addition, W/C ratios of fresh aggregate concrete were 0.48, 0.45 and 0.39. Cement content of concrete 185 kg/m3 as per (3 p. 6) for all cases. Then the specimens are cured under water continuously. The compressive strength of concrete was measured at 7, 21, 28 and 60 days by using Universal Testing Machine (UTM). The failure surfaces of concrete were also checked carefully after crushing of the concrete cube. About 72 concrete cubes were investigated for 6 cases as summarized.
Research Program
Materials collection
Fresh aggregate Demolished aggregate
Fine aggregate Cement
Test of the materials properties
Mix design
Mix ratio
Casting and curing of cubes
Compressive strength test
Compare and evaluation
Conclusion
1st International Conference on Research and Innovation in Civil Engineering (ICRICE 2018), 12 –13 January, 2018, Southern University Bangladesh (SUB), Chittagong, Bangladesh ISBN: 978-984-34-3576-7
RESULTS AND DISCUSSIONS
General
Benefits of recycled aggregate (RA) in concrete can be described in environmental protection and
economical terms. The application of recycled aggregate in construction activities has been practiced
by developed countries and also of some Asian countries. This paper reports the results of an
experimental study on the mechanical properties of recycled aggregate concrete (RAC) as compared to
natural aggregate concrete (NAC). The 100% of RA used in the concrete mix to replace the natural
coarse aggregate in concrete number 100 x 100 x 100 cube mm were cast with target compressive
strength is 21, 28 and 32 MPa within 7, 21, 28 and 60 days curing period.
Table: Finesse Modulus of fine & coarse aggregate. (4 p. 6)
Fine Aggregate F.M
Local Sand 1.33
Sylhet Sand 2.34
Combined (Local &
Sylhet)
1.83
Coarse Aggregate F.M
Recycled 4.20
Fresh 5.70
Table: Unit weight, specific gravity, absorption capacity, moisture content of fine aggregate. (4
p. 6)
Fine
Aggregate
Unit Weight
(kg/m3)
Specific
Gravity
Absorption
Capacity, %
Moisture Content,
%
Local Sand 1606 2.55 3.95 2.70
Sylhet Sand 1500 2.54 3.09 2.06
Table: Unit weight, specific gravity, absorption capacity, moisture content of course
aggregate. (4 p. 6)
Coarse
Aggregate
Unit Weight
(kg/m3)
Specific
gravity
Absorption
capacity, %
Moisture content,
%
Recycled 1235 2.14 8.64 1.70
Fresh 1628 2.73 0.70 2.06
1st International Conference on Research and Innovation in Civil Engineering (ICRICE 2018), 12 –13 January, 2018, Southern University Bangladesh (SUB), Chittagong, Bangladesh ISBN: 978-984-34-3576-7
Graphical Representation
Fig. Comparison of concrete compressive strength Recycle Aggregate Concrete (RAC) vs. Fresh
Aggregate Concrete (FAC) between Curing Periods M 21
Fig. Comparison of concrete compressive strength Recycle Aggregate Concrete (RAC) vs. Fresh
Aggregate Concrete (FAC) between Curing Periods M 28
Fig. Comparison of concrete compressive strength Recycle Aggregate Concrete (RAC) vs. Fresh
Aggregate Concrete (FAC) between Curing Periods M 32
7.5
15.6 16.3 17.611.9
20.7 20.922.6
0.0
5.0
10.0
15.0
20.0
25.0
7 21 28 60
Co
mp
ress
ive
Str
eng
th (
MP
a)
Curing Period (days)
Compressive Strength RAC vs FAC-21 MPa
Recycled Concrete
Fresh Concrete
11.2
17.8 18.0 19.616.0
23.0
27.7 28.2
0.0
5.0
10.0
15.0
20.0
25.0
30.0
7 21 28 60
Co
mp
ress
ive
Str
eng
th
(MP
a)
Curing Period (days)
Compressive Strength RAC vs FAC-28 MPa
Recycled Concrete
Fresh Concrete
13.5
21.1 22.4 22.918.1
31.6 31.9 32.1
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
7 21 28 60
Co
mp
ress
ive
Str
eng
th (
MP
a)
Curing Period (days)
Compressive Strength RAC vs FAC-32 MPa
Recycled Concrete
Fresh Concrete
1st International Conference on Research and Innovation in Civil Engineering (ICRICE 2018), 12 –13 January, 2018, Southern University Bangladesh (SUB), Chittagong, Bangladesh ISBN: 978-984-34-3576-7
Fig. Comparison of concrete compressive strength Recycle Aggregate Concrete (RAC) between
Curing Periods M21, M28, M 32
Fig. Comparison of concrete compressive strength Fresh Aggregate Concrete (FAC) between
Curing Periods M21, M28, M 32.
DISCUSSION
Concrete specimen made with the aggregate got from demolished concrete has achieved
65-84% of the strength for which it has been supposed to be designed. On the other hand,
concrete prepared from fresh aggregate showed the better performance regarding strength.
Concrete made with 100% recycled aggregates is weaker than concrete made with fresh
aggregates at the same concrete mix design. Strength reduction was 20%-30% of design
strength.
The workability of RAC is lower than FAC because the rate of the absorption capacity of RA is
higher than FA.
7.5
15.6 16.317.6
11.2
17.8 18.019.6
13.5
21.122.4 22.9
0.0
5.0
10.0
15.0
20.0
25.0
7 21 28 60
Co
mp
ress
ive
Str
eng
th (
MP
a)
Curing Period (Day)
Compressive Strength of Recycled Aggregate Concrete-
M21, 28, 32 Mpa
M 21
M 28
M 32
11.9
20.7 20.922.6
16.0
23.0
27.7 28.2
18.1
31.6 31.9 32.1
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
7 21 28 60Co
mp
ress
ive
Str
eng
th (
MP
a)
Curing Day
Compressive Strength of Fresh Aggregate Concrete - M21,
28, 32 Mpa
M 21
M 28
M 32
1st International Conference on Research and Innovation in Civil Engineering (ICRICE 2018), 12 –13 January, 2018, Southern University Bangladesh (SUB), Chittagong, Bangladesh ISBN: 978-984-34-3576-7
CONCLUSION
Based on the laboratory investigations, the following conclusions are made:
1. Concrete strength from 17.5 ~ 23.0 MPa can be obtained using recycled coarse aggregate.
2. The water requirement for all the mixes is different and especially for mixing with recycled
coarse aggregates, so workability is poor then fresh aggregate concrete.
3. The density of concrete is another important factor. The results indicates that all the concrete
mixes with recycled aggregate have less density as compared to fresh aggregate concrete.
4. Recycled aggregate is not suitable where higher strength of concrete is required.
REFERENCE
1. Influence of Type and replacement Level of Recycled Aggregate on concrete Properties.
Yang, Keun -Hyeok, Chung, Heon -Soo and Ashour, Ashraf F. June 2008, ACI Materials
Journal, pp. V.105,No.3.
2. Standard Test Method for Relative Density (Specific Gravity) and Absorption of Fine
Aggregate. American Society for Testing and Materials, ASTM. West Conshohocken, PA,
2015, ASTM International, pp. DOI: 10.1520/C0128-15.
3. Mixture Proportioning. ACI Committee,211-91. 1991, Standard Practice for Selecting
Proportions for Normal, Heavyweight, and Mass Concrete (Reapproved 2009), p. 38.
4. Aziz, Dr M. A. ENGINEERING MATERIALS . Dhaka : s.n., 1995.
5. Sustainable Development of Concrete Technology. Mohammed, Dr. Tarek Uddin.
Dhaka : Dept. of Civil Engineering (UAP).
1st International Conference on Research and Innovation in Civil Engineering (ICRICE 2018), 12 –13 January, 2018, Southern University Bangladesh (SUB), Chittagong, Bangladesh ISBN: 978-984-34-3576-7