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Influence of Binder Type on Performance of Dense Bituminous Mixture Prepared with Coarse Recycled Concrete Aggregate

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Conventional stone aggregates are becoming scare and costly because of huge infrastructure activities going on since last three decades in India. On the other hand, wastes such as that resulting from old concrete constructions are abundantly available. Many attempts have already been made to utilise these wastes referred to as recycled concrete aggregate (RCA) in various constructions including in bituminous paving layers. All types of bituminous binders commonly used in paving mixes in India may not be compatible with RCA. This experimental study aims to study the influence of binder type on the performance of dense graded bituminous mixtures containing RCA replacing the coarse fraction of conventional stone aggregates. In order to achieve this main objective, dense bituminous macadam (DBM) mixtures as per the relevant Indian specifications were prepared using three different types of bituminous binders commonly used in India, namely conventional VG 30 and VG 40 bitumens, and crumb rubber modified binder (CRMB). Separate Marshall samples were prepared using RCA and natural aggregate (NA) and either of the above three binders. As per the main scope of this study, the mixtures thus prepared were evaluated in terms of their engineering properties such as Marshall characteristics, indirect tensile strength, moisture susceptibility characteristics, resilient modulus and rutting resistance. It is observed that all mixtures considered in this study, in general satisfy the requirements in terms of Marshall and moisture susceptibility characteristics. Considering all engineering properties studied, the CRMB/VG40 bitumen offer superior and satisfactory results for mixtures containing either NA or RCA, with NA showing slightly better result as compared with RCA in the mixtures.
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Influence of Binder Type on Performance of Dense Bituminous Mixture
Prepared with Coarse Recycled Concrete Aggregate
Jagadeesh Gopalam, Jyoti Prakash Giri, Mahabir Panda
PII: S2214-5095(20)30085-1
DOI: https://doi.org/10.1016/j.cscm.2020.e00413
Reference: CSCM 413
To appear in: Case Studies in Construction Materials
Received Date: 3 December 2019
Revised Date: 2 August 2020
Accepted Date: 3 August 2020
Please cite this article as: Gopalam J, Giri JP, Panda M, Influence of Binder Type on
Performance of Dense Bituminous Mixture Prepared with Coarse Recycled Concrete
Aggregate, Case Studies in Construction Materials (2020),
doi: https://doi.org/10.1016/j.cscm.2020.e00413
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© 2020 Published by Elsevier.
1
Influence of Binder Type on Performance of Dense Bituminous
Mixture Prepared with Coarse Recycled Concrete Aggregate
Jagadeesh Gopalam1*, Jyoti Prakash Giri2, Mahabir Panda3
1 P.G. Student, Department of Civil Engineering ,GMR Institute of Technology, Civil
Department, Rajam, India, Email: jagadeesh1329@gmail.com.
2 Assistant Professor, Department of Civil Engineering ,GMR Institute of Technology, Civil
Department, Rajam, India, Email: jyotiprakash.g@gmrit.edu.in.
3 Professor, Department of Civil Engineering,National Institute of Technology, Civil
Department, Rourkela, India, Email: mpanda@nitrkl.ac.in.
Abstract
Conventional stone aggregates are becoming scare and costly because of huge infrastructure activities going on
since last three decades in India. On the other hand, wastes such as that resulting from old concrete constructions
are abundantly available. Many attempts have already been made to utilise these wastes referred to as recycled
concrete aggregate (RCA) in various constructions including in bituminous paving layers. All types of bituminous
binders commonly used in paving mixes in India may not be compatible with RCA. This experimental study aims
to study the influence of binder type on the performance of dense graded bituminous mixtures containing RCA
replacing the coarse fraction of conventional stone aggregates. In order to achieve this main objective, dense
bituminous macadam (DBM) mixtures as per the relevant Indian specifications were prepared using three different
types of bituminous binders commonly used in India, namely conventional VG 30 and VG 40 bitumens, and
crumb rubber modified binder (CRMB). Separate Marshall samples were prepared using RCA and natural
aggregate (NA) and either of the above three binders. As per the main scope of this study, the mixtures thus
prepared were evaluated in terms of their engineering properties such as Marshall characteristics, indirect tensile
strength, moisture susceptibility characteristics, resilient modulus and rutting resistance. It is observed that all
mixtures considered in this study, in general satisfy the requirements in terms of Marshall and moisture
susceptibility characteristics. Considering all engineering properties studied, the CRMB/VG40 bitumen offer
superior and satisfactory results for mixtures containing either NA or RCA, with NA showing slightly better result
as compared with RCA in the mixtures.
Keywords: Recycled concrete aggregate, Crumb rubber modified bitumen, Moisture susceptibility, Resilient
modulus, Flow number.
1. Introduction
For construction and maintenance of bituminous pavements there is a huge requirement of aggregates
which are normally processed from natural stone resources. As these resources are fast depleting and hence
becoming costlier, highway engineers and researchers are looking for waste and locally available materials to
replace the natural stone aggregates to the extent possible. One of the waste materials which have been tried in
road construction replacing aggregates, is concrete waste. The construction and demolition (C&D) waste from
concrete structures when processed and reused as aggregates in new construction works are referred to as recycled
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concrete aggregates (RCA). A number of studies [1] have been made to understand the potential of RCA for use
in bituminous mixes. Though the applications of RCA in different works are wide, till date limited works are
available on the use of RCA as an aggregate in bituminous mixtures for paving applications. This is because of
the fact that the physical, chemical and mechanical properties of RCA are quite different from that of the
conventional stone aggregates. Basically, RCA is rough, porous and irregular in shape, having lower specific
gravity and higher water absorption value as compared with conventional aggregates [2]. Further, with
heterogeneous sources and variant crushing process, the composition of RCA varies widely and the resulting
bituminous mixtures incorporating RCA offers controversial characteristics [3]. However, some studies report that
the performance characteristics of HMA mixtures containing RCA, such as resistance to moisture induced damage,
rutting resistance, fatigue life and low temperature cracking resistance have similar trends of improvement as that
with the conventional bituminous mixture [4, 5, 6]. One drawback of using RCA in HMA is that the mixture has
higher bitumen requirement as compared with conventional bituminous mixtures with NA [3]. However, this
difference of consumption of bitumen was more apparent when RCA was used in finer fraction in the mixture [7].
To counteract the above problem of high bitumen requirement and at the same time maintain required performance
standards, Bhusal et al. [8] suggested to incorporate only coarse fraction of RCA in hot mix asphalt (HMA).
The performance characteristics of bituminous mixtures are linked with aggregate properties like
strength, and stiffness. Further, it is necessary to understand the aggregate characteristics appropriately with
bitumen in a bituminous mixture [9]. Kok et al. [10] concluded from their experimental investigation that, when a
bituminous mixture was prepared with conventional aggregate and crumb rubber modified bitumen (CRMB), it
was more suitable for combating low-temperature cracking in colder climates because it reinforced immediately
after crack initiation. In this respect, the use of crumb rubber (CR) was preferred over styrene-butadiene-styrene
(SBS) for modification of bitumen. The use of CR in modification of virgin bitumen also offers environmental
benefits (waste utilisation) as well as a significant cost savings due to the high cost of SBS. Similarly, Moghaddam
et al., [11] observed that, the bituminous mixtures made with modified bitumen offered better results in terms of
stability, durability, workability, compaction and resistance to deformation compared to mixture compacted with
conventional bitumen and natural aggregate. Hence, generally it is observed that the performance of bituminous
mixture is significantly affected due to the aggregates and binder types used for preparing a mixture.
Based on the above facts, the main objective of this experimental work is to study the performances of
bituminous mixtures prepared with RCA in conjunction with different types of bituminous binders normally used
in the field. In this study, RCA fully replaces the coarse aggregate fraction in the dense bituminous macadam
(DBM) mixture and cement has been used as filler. The binders used in this study are conventional VG 30 and
VG 40 bitumens and one modified binder CRMB, to study the effects of binder types on the mixture performances.
For comparison purposes, the DBM mixes were also prepared using conventional natural aggregates (NA).
2. Experimental Program
In the present study, in order to study the effects of aggregate and bitumen types on the performance of
dense bituminous macadam (DBM) mixes, six combinations (with two types of aggregates, i.e., NA, and RCA,
and three types of bitumens, i.e., CRMB, VG 40, and VG 30) were tried. As mentioned earlier cement (CM) was
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used as filler for preparation of the paving mixtures. For each mixture type, performance tests such as Marshall
characteristics, indirect tensile strength, moisture susceptibility in the form of tensile strength ratio (TSR) and
retained stability (RS) and resilient modulus test, were conducted. A flowchart of the present experimental
investigation is presented in Fig. 1.
Fig 1. Flowchart of the present experimental investigation
2.1 Materials
In this study, two types of aggregates namely NA and RCA were used. The demolition concrete was
collected from the campus of GMR Institute of Technology (GMRIT), Rajam resulting from the specimens cast
for testing and research purposes in the concrete laboratory. Then the concrete debris were first crushed with a
jaw crusher and appropriately sieved out to obtain the required size fractions of RCA. The natural aggregates were
collected from a local government approved stone quarry for the preparation of bituminous mixtures. The physical
properties of RCA and NA were determined in the laboratory and these results were summarised in Table 1. From
this table it may be observed that RCA has a relatively low specific gravity with high water absorption value
compared to natural aggregate. The reason behind this may be the thick cement mortar adhering to the aggregates
of the RCA which create a porous structure, as may be observed from the SEM images given in Fig. 2. It can be
noticed from this figure that, there was presence of a large amount of voids and microfractures on the surface,
which may lead to lower strength, higher water absorption and poor adhesion with bitumen. Though other physical
properties like impact value, aggregate crushing value, and Los Angeles abrasion value were found to be
satisfactory for RCA according to Ministry of Road Transport and Highways (MoRTH) specifications [12], these
were somewhat inferior compared to NA.
Preparation of bituminous mixtures
Natural aggregate (NA)
Demolition concrete waste (RCA)
Crushed and converted to required
coarse aggregate fraction ( > 4.75mm)
Coarse aggregates
(RCA and NA )
Fine aggregates (NA)
Filler (Cement, stone dust,
fly ash and carbon black)
Bitumen (VG 30)
Marshall mix design
(DBM gradation, MoRTH,2013)
Determination of OBC
(eight mixtures)
Performance test
of DBM mixtures
Determination of physical
properties of different used materials
Indirect tensile strength Moisture susceptibility Resilient modulus Flow number
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Fig. 2. Scanning electron microscopy images of (a) NA and (b) RCA
For preparation of DBM mixtures with 26.5 mm nominal maximum aggregate size, the mid-point grading
as per MoRTH given in Fig. 3 was adopted [12]. The Portland slag cement having specific gravity of 3.01,
procured locally was used as filler.
Three types of bituminous binders such as, two conventional bitumens, i.e. named as CRMB, VG 40
bitumen, and VG 30 bitumen were used as binder material for preparing the bituminous mixtures. The latter two
were used in this study as these are commonly used in India for construction of bituminous paving layers according
to IRC 37 [13] and MoRTH specifications [12]. The basic physical properties of the three types of bituminous
binders used are presented in Table 2.
Table 1. Physical properties of NA and RCA
(a) NA
(b) RCA
Property
Test method
Test Results
Recommended value
[12]
NA
RCA
Aggregate impact value (%)
15
26
<30
Aggregate crushing value (%)
14
28
<30
Los Angeles abrasion value (%)
21
31
<40
Flakiness index (%)
21
22
<30
Elongation index (%)
22
24
Water absorption (%)
0.28
4.8
<2
Specific gravity
2.78
2.48
Stripping value (%)
1.5
4.7
<5
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Fig. 3. Gradation curve for DBM mixture [12]
Table 2 Physical properties of different binders used
Property
Test Method
Test Results
Recommend value
[23]
VG 30
VG 40
CRMB
Specific gravity (27oC)
[18]
1.01
1.09
1.05
> 0.99
Penetration at 25°C (0.1
mm)
[19]
66
58
52
> 50
Ductility at 27oC (cm)
[20]
78
82
88
> 75
Softening Point (27°C)
48
52
62
> 47
Absolute viscosity at
60°C (Poise)
[21]
2545
2689
2898
2400-3600
Kinematic viscosity at
135°C (cSt)
[22]
418
438
487
> 350
2.2 Preparation of Bituminous Mix Sample
Marshall test as per ASTM D1559 [24], is a basic and low-cost standard laboratory test adopted in many
parts of the world including in India for design of bituminous mixtures and using the same in construction. The
same procedure has been considered in this study to determine the optimum binder content (OBC) of different
mixtures considered and also to evaluate the mixture. In this experimental study, six different mixture
combinations of DBM were considered containing RCA and NA for coarse aggregate fraction, with CM as filler
and three types binders such as CRMB, VG 40 and VG 30 bitumen. In all these six mixtures, stone dust was used
for the fine aggregate fraction. These six bituminous mixtures have been designated in this study as RCA CRMB,
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RCA 40, RCA 40, NA CRMB, NA 40, and NA 30 where the preceding word represents the material of the CA
fraction and the succeeding one represents the type of binder used. Three specimens were prepared for each trial
bitumen content for a particular mixture.
2.3 Indirect Tensile Strength test
Indirect tensile strength (ITS) test is generally considered for observing the tensile strength properties of
bituminous mixture which can further be related to rutting and cracking properties [11]. This test method is
performed according to ASTM D6931 [25] at three test temperature of 15oC, 25oC and 35oC in the present study.
In this test the cylindrical Marshall specimens are placed between two loading strips and subjected to compressive
loads, in a vertical diametric plane. The ITS value of a specimen can be calculated by using Eq. (1).
ITS 
 (1)
Where,
ITS - Indirect tensile strength (kPa)
P - Maximum load (N)
H - Specimen thickness (mm)
D - Specimen diameter (mm)
2.4 Tensile Strength Ratio Test
Moisture induced damage is generally a primary cause of distress in bituminous mixtures, particularly in
areas where water remains stagnant for a considerable time. In order to assess the possibility of moisture induced
damage to bituminous mixtures, tensile strength ratio (TSR) is generally used. The tensile strength ratio is the
ratio between indirect tensile strength of the water-conditioned specimens to that of dry specimens, expressed as
percentage. The samples were conditioned in the laboratory and tested according to AASTHO T283 [26]. These
conditioned specimens are tested for their tensile strength and the TSR value of the bituminous samples is
calculated by using Eq. (2).
TSR (%) 
  (2)
2.5 Retained Stability test
This retained stability test (RS) is another test to assess the moisture susceptibility properties of
bituminous mixtures. The test is conducted on the conventional Marshall samples using Marshall test as per
ASTM D1075 [27]. In this test, the Marshall stability is determined before and after the moisture conditioning
process of the compacted specimens. The specimens are considered as conditioned when they are immersed in
water at 60°C for 24 hrs, and are said to be unconditioned when they are as usual kept in water bath at 60°C for
about half an hour. To determine the resistance of mixtures to loss of adhesion in the presence of moisture, the
retained stability is evaluated by using Eq. (3).
RS    
   (3)
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2.6 Resilient Modulus Test
The resilient modulus of a bituminous mixture is an important parameter used in the analysis and design
of a pavement [28]. In this test, a repeated load is applied to the Marshall samples (prepared at their respective
OBC) in an indirect tensile test set-up, and the resilient horizontal and vertical deformations are measured. For
this purpose, a repeated load customized test setup is used in the laboratory and the test is conducted as per ASTM
D 4123-82 [29]. In the present laboratory study, resilient modulus test is done at the most prevailing test
temperature of 25ºC and the loading frequency is selected as 1 Hz with loading time and rest period of 0.1s and
0.9s respectively. The repeated load considered for this test was about 25% of static ITS test result obtained for a
particular bituminous mixture at that particular test temperature.
2.7 Flow Number
The flow number test is conducted using Asphalt Mixture Performance Tester (AMPT). According to
specification AASHTO TP79 [30], the bituminous mixture is tested at temperature of 25 to 60°C. The resulting
permanent axial strain is measured as a function of time and is numerically differentiated to calculate flow number
values [2]. NCHRP Project 933 suggests an axial stress of 600 kPa for the unconfined flow number test on
specimens with a target air void of 7% [31]. The flow number test specimens were prepared using Superpave
Gyratory Compactor (SGC) at 7% air void content having a size of 150 mm diameter and height of 170 mm. Then
the same was cored out from the 150-mm-diameter specimens and then trimmed on both sides. Two replicate
specimens were prepared for each bituminous mix with 100-mm diameter and 150-mm height and the specimens
were tested at 54°C.
3. Results and Discussion
3.1 Marshall Characteristics
The results of the Marshall tests including volumetric characteristics are presented in Table 3. From
Table 3, it is observed that the mixture containing RCA has resulted in higher stability value, whereas the unit
weight is found to be higher for the conventional bituminous mixture (with NA). The reason behind the higher
Marshall stability value in case of RCA sample may be due to rough surface of RCA resulting a good bonding
between aggregate particles in the mixture. The lower unit weight of mixture containing RCA is obviously due to
lower specific gravity of RCA itself. It is seen that all these mixtures satisfy the Marshall criteria required as per
MoRTH specifications [12]. The OBC is determined at 4% air void content in the mix according to MoRTH [12]
specifications and the observed OBC values for the six different bituminous mixtures are presented in Table 3. It
can be observed from this table that, there is more bitumen requirement for mixtures prepared with RCA. This is
because of the fact that the porosity of the mortar attached to the RCA surface tends to absorb some extra amount
of bitumen. Pasandín and Pérez [32] also reported that HMA containing RCA requires more binder as compared
to the mixture containing NA, thus corroborating this research finding.
Table 3 also presents the Marshall ratio values of the mixes. The Marshall ratio, a ratio of Marshall stability to
flow value of a Marshall sample. As per Pasandín and Pérez [33], this parameter is used to relate the stiffness of
the mix, and the mixtures with higher Marshall ratio offer greater resistance to permanent deformation. It is
observed in this study that the mixtures prepared with RCA result in higher Marshall ratio, which is an advantage.
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Table 3. Marshall characteristics of different DBM mixtures
Mix type
Unit Weight
(kN/m³)
VFB (%)
VMA
(%)
Marshall
Stability
(kN)
Flow
(mm)
Marshall
ratio
(kN/mm)
OBC (%)
NA 30
23.82
15.9
70
13.7
3.5
3.91
5.1
RCA 30
22.58
15.2
75
15.2
3.6
4.22
5.37
NA 40
24.52
15.3
74
16.2
3.15
5.14
5.03
RCA 40
22.60
14.8
77
18.8
2.95
6.37
5.33
NA CRMB
24.26
15.6
73
15.7
3.4
4.62
5
RCA CRMB
22.76
14.9
75
18.3
3.15
5.81
5.26
3.2 Indirect Tensile Strength Test
The effects of aggregate and bitumen type on ITS value of the mixtures are presented in Fig. 4. It is found
that as usual the ITS value decreases with increase in test temperature for each type of mixture considered. The
samples prepared with NA and VG 40 bitumen showed lower ITS values at the lower test temperature, but offered
higher ITS value at higher test temperature. Similar trend is also followed for the mixture prepared with RCA and
CRMB. However, the mixture with NA and VG 30 bitumen resulted in higher ITS value at lower test temperature
and lower ITS value at higher test temperature. The results of ITS of the mixes with NA and VG 30 bitumen
almost match with the study by Giri et al. [2]. The reason behind the result of mix with NA and VG 40 bitumen
may be due to the fact that VG 40 bitumen having higher stiffness produces higher resistance at higher
temperature, however at lower temperature this bitumen may be somewhat brittle to resist the tensile stress
developed. CRMB on the other hand might not have completely coated the rough porous RCA as compared with
VG 30 bitumen causing its inability to resist the tensile stress at lower temperature, though it has higher stiffness
at higher temperature to result in higher tensile strength of the mix.
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Fig. 4. Indirect tensile strength test for DBM mixes at various test temperatures
3.3 Tensile Strength Ratio
The results of the tensile strength ratio (TSR) of the mixes are presented in Fig. 5. It is observed that, the samples
prepared with NA and VG 40 bitumen offered highest TSR values among all mixtures, whereas the mixtures
prepared with RCA also offered good moisture susceptibility characteristics. However, all the six mixtures are
found to satisfy the TSR requirement of 80% as recommended by MoRTH [12]. In general, for a particular binder
used, NA offers higher TSR value as compared with RCA. This may be because of higher porosity and lack of
complete coating around RCA particles. Therefore, it can be concluded that the RCA may be effective in
satisfactorily resisting the moisture induced damages. The results are consistent with the findings of Pasandín and
Pérez [32] where they observed that the hot mix asphalt containing construction and demolition waste is quite
satisfactory in respect of the stripping resistance.
Fig. 5. Tensile strength ratio value for DBM mixes
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3.4 Retained Stability Test
The results of the retained stability tests are presented in Fig. 6 and similar trends were observed as in
case of the TSR test results. As in case of TSR test result, because of higher aggregate crushing value of NA and
better stiffness characteristics of VG 40 bitumen at higher temperature, the samples prepared with NA and VG 40
bitumen resulted in somewhat higher RS values compared with other types of mixtures. The similar trends were
also reported by Giri et al. [2].
Fig. 6. Retained stability value for DBM mixes
3.5 Resilient Modulus
The results of the resilient modulus test conducted at test temperature of 25o C are presented in Fig. 7. It
is observed that samples prepared with NA and CRMB resulted in higher resilient modulus followed by mixture
made with NA and VG 40 as compared with other mixtures. Overall, the mixture prepared with CRMB as binder
material offered higher resilient modulus value as compared with the mixtures with other two types of bitumen
considered in the study. This may be due to a known fact that CRMB contributes to higher modulus because of
the effect of rubber in the binder (Behl et.al, [33]. RCA in general contributes to somewhat lower resilient modulus
of a mix with a particular binder, as compared with NA possibly because of lower strength of RCA.
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Fig. 7. Resilient modulus value for DBM mixtures
3.6 Flow number
Fig. 8 shows the results for flow number for the six selected DBM mixtures. The test is run for 10,000
loading cycles or until an accumulated permanent strain of 50,000 micro strains is reached. Test results represented
in the Fig. 8 represent the average of the flow number values of two specimens of a particular selected mixture.
From the figure it may be observed that the mixture prepared with RCA and VG 30 results in the lowest flow
number and the mixture made with NA and CRMB offered highest flow number. The interesting fact is that when
CRMB is used, there is a dramatic increase in flow number, indicating much better rutting resistance for the
mixtures. This may be attributed to the properties of CRMB at higher temperature such as higher softening point
and viscosities as presented in Table 1. Use of CRMB in paving mixes for better rut resistance has been reported
by Kok et al. [10] and Behl et al. [34] which justifies the present finding.
Fig. 8. Flow number value for DBM mixtures
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4. Conclusions
From the experimental investigations carried out in the present study on effects of binder type on the DBM
mix characteristics the following important conclusions are drawn.
RCA in general contributes to highest Marshall stability value as high as 19 kN. Both VG 40 bitumen
and CRMB as binders also contribute to substantial Marshall stability value. All types of mixtures
considered including that containing RCA result in satisfactory Marshall characteristics as per
MoRTH specifications.
The mixtures prepared with NA and VG 40 offer higher ITS values as compared with other types of
mixtures at a particular test temperature.
In respect of moisture susceptibility characteristics, in general the mixture with NA and VG 40
bitumen contributes the best result in terms of TSR value and retained stability value. However, all
types of mixtures considered in the study including that made with RCA satisfied the minimum
requirements for the same as per MoRTH specifications.
The mixture prepared with NA and CRMB results in much higher resilient modulus value slightly
followed by the mixture with RCA and CRMB.
Similar trend is also observed for the mixtures in the flow number test indicating much superior
resistance to rutting in respect of mixtures made with NA and CRMB. RCA offered slightly less
flow number as compared with NA in respect of mixture with any particular binder used.
From the above summary of test results, it is concluded that the recycled concrete aggregate which is available
in huge quantities as a waste material, in conjunction with CRMB or conventional VG 40 bitumen in general
offers superior test results, and hence can be utilized as an alternative to fast depleting and costly natural stone
aggregates for sustainable development of bituminous road infrastructure.
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
Acknowledgement and Funding information
Not Applicable.
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aggregates and crumb rubber. Journal of Cleaner Production 2017; 165: 405-414.
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