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ASSESSING THE INFLUENCE OF AGING ON ASPHALT CONCRETE PROPERTIES

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 1, January 2019,
201 pp.128–142, Article ID: IJCIET_10_01_013
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
0976
©IAEME Publication
Scopus Indexed
ASSESSING THE INFLUENCE
INFLUENCE OF AGING ON
ASPHALT CONCRETE PROPERTIES
PROPERTIES
K. H. Sultan
Department of Civil Engineering,
Engineering University College of Esraa, Baghdad, Iraq
A. H. Alwan
Department of Civil Engineering,
Engineerin , University College of Esraa, Baghdad, Iraq
M. H. Hameed
Department of Civil Engineering,
Engineering, University College of Esraa, Baghdad, Iraq
ABSTRACT
Aging is one of the real issues that confronting flexible pavement through the
service life of pavement. The physical and chemical properties of asphalt cement are
change after a period of time.
time Aging are happens during the preparation of mixtures,
service life and when exposed to the different climatic conditions. For the purpose of
this study local materials have been brought and tested. The local materials are
including asphalt cement, coarse and fine aggregate and mineral fillers. In this work,
Portland cement and silica fume were used as mineral filler. Two types of specimens
were prepared and tested.
tested The first type was included 100 % Portland cement as
mineral filler and the second type was included 50 % Portland cement and 50 % silica
fume as mineral filler. The optimum asphalt content of mixtures
mixture was found according
to Marshall Design method. Optimum asphalt content
c
of mixture was 4.9 for
specimens that contain 100 % Portland cement as mineral filler and it was 5.1 % for
specimens that contain 50 % Portland cement and 50 % silica fume as mineral filler.
filler
Fifty one (51)) of asphalt concrete specimens (Marshall Specimens)
Specimens) were prepared.
For the purpose of studying the effect of short term aging, part of specimens was
placed in the oven and subjected it to a temperature of 135 ºC for (2 and 4 hr), while
for the long term aging, another part of specimens was placed in the oven and
subjected it to a temperature of 85 ºC for 72 hr (3 days) and 120 hr (5 days) according
to AASHTO R30. The results of Marshall Test showed that the stability of Marshall
was increased by 13.63%, 27.27%, 51, 81 and 63.63% after S.T.A (2 and 4)hr
4
and
after L.T.A(3 and 5) days, respectively. Flow of Marshall was decreased after S.T.A (2
and 4) hr and after L.T.A (3
( and 5) days by 8.82%, 14.7%, and 35.29 % and 38.23%.,
respectively. Also, the results showed that the air voids in total mixture were increased
after short and long term aging. Generally, the results showed that the use of 50%
silica fume as a mineral filler with 50 %Portland cement leads to change the influence
of aging on properties of Marshall by different percentages.
percentages
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K. H. Sultan, A. H. Alwan and M. H. Hameed
Key words: Portland Cement, Silica Fume, Properties of Marshall, S.T.A and L.T.A.
Cite this Article: K. H. Sultan, A. H. Alwan and M. H. Hameed, Assessing The
Influence of Aging on Asphalt Concrete Properties, International Journal of Civil
Engineering and Technology (IJCIET), 10 (1), 2018, pp. 128–142.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1
1. INTRODUCTION
Aging is considered as one of the real issues that influence performance of flexible pavement
because modes of failure like rutting, thermal cracks and fatigue cracks affect performance of
pavement. Therefore, aging phenomena is a reason of failure for each mode of failures [1].
The physical and chemical properties of asphalt cement usually change with time. Asphalt
cement become more brittle and stiff after period of time which is alluded to aging of asphalt.
These altered properties directly effect on the performance of flexible pavement. [2].Aging of
asphalt cements happens during two phases. The first phase of aging happens at a very quick
rate when asphalt cement is blends with coarse and fine aggregates and heated to required
temperatures of mixing; therefore, this phase is referred to short term aging (S.T.A). The last
phase of aging happened at a low rate after the mixtures are set down then spread and
compacted. Aging proceeds for around (2 to 3) years after construction until the mixture
arrive to the maximum bulk density. This phase is alluded to long term aging (L.T.A). Aging
of asphalt cement essentially influences the mechanical properties of mixture and
consequently influence the performance of the flexible pavement. So, it is necessary to
describe the aging of asphalt mixtures properly for the fruitful design of flexible pavements
[3].The influence of aging of asphalt cement on the performance of mixture has been
examined according to two methods. The first one is subject different testing conditions to
asphalt cement and after that find the changes in the physical properties to evaluate the
possibility of aging of the asphalt cement, so this method does not take into consideration the
impact of particles of coarse and fine aggregate and does not give realistic expectation to the
performance of the pavement. The last method is exposing the mixture of asphalt to different
testing aging conditions and after that the physical properties of the aged mixtures is
determined. This last method is more accurate because the processes of aging are directly
performed on the mixtures [4]. At normal temperatures asphalt cement is a dark, semisolid
and highly viscous material. It is known as a thermoplastic material because it is soft at high
temperature and hardens at low temperature. For preparing of mixture the temperature of
asphalt cement should not exceed the manufacturer recommended temperature at heating.
Oxidation will be happened if the asphalt cement is heated more. Oxidation makes asphalt
cement more brittle that leading to aging. A lot of amount of hardening (aging) happens
during production of hot mix asphalt when the asphalt cement is heated to facilitate process of
mixing and then compaction. In general, more aging of asphalt cement is not desirable
because it may be decreases durability of pavement [5].Moreagingcan be weaken the bonding
between asphalt cement and aggregate, for this reason, loss of materials will be occur sat the
surface layer, so, aging of asphalt cement is important factor for the durability of flexible
pavements [6,7].
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2. EXPERIMENTAL WORK
2.1. Material Characteristics
2.1.1. Asphalt Cement
In this study, asphalt cement of penetration grade of (40-50) was used. It was from Dura
refinery. The main physical properties of this asphalt cement are recorded in Table 1.
Table 1 Physical Properties of Asphalt Cement.
Property
Conditions of
Test
Specification
Used
Results of Test
SCRB (2003)
Specification
Penetration
(25˚C, 100 gm.,
5 sec, 0.1 mm)
---(25 ˚ C, 5
cm/min)
---25˚C
ASTM D 5
41.5
40 – 50
ASTM D 36
ASTM D 113
42
>100
--->100
ASTM D 92
D-70
310
1.04
>232
----
Softening Point
Ductility
Flash Point
Specific Gravity
2.1.2. Aggregate
Coarse and fine aggregates were gotten from the quarry of alnibaei. Physical properties of
coarse and fine aggregate are showed in Table 2.
Table 2 Physical Properties of Coarse and Fine Aggregate.
Property
Coarse Aggregate
Results of
Specification used
Test
Bulk Specific
Gravity
Apparent Specific
Gravity
Absorption of Water
%
Los Angles
(Abrasion % )
Fine Aggregate
Results of Specification used
Test
2. 542
ASTM C 127
2.58
ASTM C 128
2.57
ASTM C 127
2.62
ASTM C 128
0.62%
ASTM C 127
1.01%
ASTM C 128
16.36%
ASTM C 131
----
----
2.1.3 Mineral Fillers
In this study, Portland cement and Silica fumes were used as mineral filler. Table 3 shows
physical properties of the considered types.
Table 3 Physical Properties of Portland Cement and Silica Fume.
Filler Type
Physical Properties
% Passing Sieve No. 200
Specific Gravity
96.4
98.4
3.15
2.623
Portland Cement
Silica Fume
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2.2. Selected Gradation of Aggregate
The gradation of aggregate that utilized in this investigation following the specification of the
commission of state of roads and bridges (SCRB 2003) with 19 mm maximum aggregate size.
Figure 1and Table 4 show the selected gradation of aggregate.
Figure 1 Selection of Aggregate Gradation According to SCRB (2003).
Table4 Specification of Aggregate Gradation for Surface Layer.
Sieve
Openin
g (mm)
19
12.5
9.5
4.75
2.36
0.3
0.075
Sieve Size
3/4"
1/2"
3/8"
No.4
No.8
No.50
No.200
% Passing by Weight
SCRB Specification
Selected Gradation
Limits
100
100
95
90 – 100
83
76 – 90
59
44 – 74
43
28 – 58
13
5 – 21
7
4 – 10
2.3. Preparation of Specimens of Marshall
Twenty four (24) of specimens of Marshall were prepared and tested in this study to obtained
optimum asphalt content (O.A.C). To acquired optimum asphalt content of mixtures, four
percentages of asphalt cement were used (4, 4.5, 5 and 5.5) %. Twenty seven (27) specimens
of Marshall were prepared according to the O.A.C to studying the aging under different
conditions.
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2.3.1. Preparation of Control Mixture
The preparation of specimens was as indicated by ASTM D1559. The aggregate was sieved
to meeting aggregate gradation requirements and after that washed and dried. Coarse and fine
aggregates were joined with mineral filler the purpose of meeting the requirements of the
gradation. Coarse aggregate, fine aggregate and mineral filler were heated in oven. Asphalt
cement was heated in oven before mixing and after that it was added to coarse aggregate, fine
aggregate and mineral filler and blended on hot plate and continue to blend until all particles
of aggregate completely covered with asphalt cement. The diameter of the mold is 10.16 cm
and the height of the mold is 6.35 cm. Filter papers were putted in the base of the mold. The
mixtures were prepared and after that putted in the mold.75 blows were implemented to each
face of the specimens using compaction hammer. Specimens are left within the molds to cool
for approximately 16 hr. finally; specimens are extracted from the molds. Figure 2 shows
phases of preparation of Specimens of Marshall.
2.3.2. Preparation of Aged Mixtures with Short Term Aging (S.T.A)
The preparation of mixtures with short term aging (S.T.A) was similar to the preparation of
control mixture but with aging. The loose mixture was putted in a pan and it was putted in the
oven for (2 and 4 hr.) at a temperature of 135 °C. The loose mixture was stirred every one
hour. The mixtures were removed from the oven after time of aging. After that, the mixtures
were compacted using hammer of Marshall. Short aging was completed according to
AASHTO R30. Similar procedure was done to prepare other specimens by replacing the
Portland cement by silica fume as mineral filler (50% Portland cement and 50% silica fume).
2.3.3. Preparation of Aged Mixture with Long Term Aging (L.T.A)
The process of long term aging (L.T.A) was done by exposure the loose mixture to S.T.A(4
hr.) and after that compacted the loose mixtures using hammer of Marshall to obtain
specimens. The prepared specimens were putted in the oven at a temperature of 85 °C for 3
days (72 hr.) and 5 days (120 hr.). When the time of long aging is completed, the specimens
were extracted from the oven to cooling for approximately 16 hr. L.T.A was done according
to AASHTO R30. Same procedure was done to prepare other specimens by replacing the
Portland cement by silica fume as mineral filler (50% Portland cement and 50% silica fume).
A -Sieve Analysis of Aggregate.
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B - Preparation of Aggregate Sample.
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C -Preparation of required asphalt.
D - Compaction of Specimens.
E - Parts of Specimens.
Figure 2 Phases of Preparation of Specimens of Marshall
3. DETERMINATION OF MARSHALL PROPERTIES
3.1. Determination of Stability and Flow of Specimens
The testing of specimens for stability and flow were completed based to ASTM D1559 .This
method measure of the resistance of specimens to flow. The specimens were placing in the
water bath and conditioning it for 30 minutes at 60 °C. The rate of loading was
50.8(mm/min.). The loading was increased to reaching to a maximum value. The loading is
stopped and the greatest value of loading is recorded when the load begins to decrease. There
is another dial gauge measures the flow of specimens during the loading .The value of flow
was recorded at the same time of recording the greatest value of load. In this study, three
specimens were tested and the average result is calculated.
3.2. Maximum Theoretical Specific Gravity
The maximum theoretical specific gravity of asphalt mixtures are influenced by the types and
contents of aggregates and asphalt cement. It is used to find total air voids (VTM) in
compacted asphalt mixtures. The maximum theoretical specific gravity (G
) of specimens
can be found using the following formula:
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=
.
.
.
.
.
.
(1)
.
Where:
w :Total Weight of Specimen (1200 gm.),
w . :Weight of Asphalt Cement, (gm.),
G . ∶Specific Gravity of Asphalt Cement,(gm/
),
w . : Weight of Coarse Aggregate,(gm.),
G . :Specific Gravity of Coarse Aggregate,(gm/
),
w . : Weight of Fine Aggregate, (gm.),
G . :Specific Gravity of Fine Aggregate,(gm/
),
w : Weight of Mineral Filler, and (gm.)
).
G : Specific Gravity of Mineral Filler (gm/
3.3. Bulk Specific Gravity (
The bulk specific gravity (G
!
)
) of specimens can be found using the following formula:
"
#$%
=
…
(2)
where:
A = Weight of Dry Specimen in Air, (gm.)
B = Weight of Saturation Surface Dry of Specimen,(gm.), and
C = Weight of Specimenimmersed in Water (gm.).
3.4. Voids in Total Mixture (V.T.M)
The V.T.M are the voids in the compacted mixture that isn't involved by asphalt and
aggregate. The V.T.M can be obtained using the following formula:
% *. +. , = -. −
Where:
G
G
0 × .2
(3)
∶ Bulk Specific Gravity, (gm/
),
∶ Maximum Theoretical Specific Gravity (gm/
).
3.5. Voids in Mineral Aggregate (V.M.A)
The spaces that found between the aggregate particles in compacted specimens is called the
voids in the mineral aggregate (V.M.A).It is including spaces filled with asphalt. V.M.A can
be obtained by using the following formula:
% *. ,. 3 = -.22 −
!6
=
5 .
.
.22
5 .
.
5 .
∗ 5
0
…
(4)
..
(5)
where:
Gb :Bulk Specific Gravity,(gm/
),
P . :Percent of Aggregate, %
G : Bulk Specific Gravity of Aggregate (gm/
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P .: Percent of Coarse Aggregate, %
G .: Specific Gravity of Coarse Aggregate, (gm/
),
P . : Percent of Fine Aggregate, %
G . : Specific Gravity of Fine Aggregate, (gm/
),
P : Percent of Mineral Filler, % and,
G : Specific Gravity of Mineral Filler (gm/
).
3.6. Voids Filled with Asphalt (V.F.A)
The voids filled with asphalt (V.F.A) are the voids in the compacted specimen that are filled
with asphalt. The V.F.A can be calculated using the following formula:
% *. 9. 3 =
:.;." $ :.<.;
:.;."
…
(6)
Where:
V. M. A = Voids in Mineral Aggregate, %
V. T. M = Voids in Total Mixture %.
4. TEST RESULTS AND DISCUSSION
4.1. Optimum Asphalt Content (O.A.C)
To find (O.A.C) for surface layer, the average value of asphalt content was taken that
corresponds of maximum stability; maximum bulk specific gravity and 4 % air voids. Flow,
VMA and VFA are achieved to affirm required limits that specified in SCRB specification.
Figure 3 and 4 show the relationship between content of asphalt and Properties of Marshall of
specimens. O.A.C of mixture was 4.9 for specimens that contain 100 % Portland cement as
mineral filler and it was 5.1 % for specimens that contain 50 % Portland cement and 50 %
silica fume as mineral filler.
4.2. Effect of Aging Time on Marshall Properties
Figure (5 - a) and (5 - b) show influence of time of aging on Properties of Marshall. It is clear
from figure (5 - a) that the Marshall stability after 2 and 4 hr (short term aging) is higher than
that of control mixture by 13.63% and 27.27%, respectively. In the long term aging, the
stability was increased by 51.81 % and 63.63% after 3 and 5 days, respectively. The
increasing of stability with time of aging may be because the losses of volatiles which make
the asphalt concrete stiffer and can resist the deformation of tested specimens. It can be
obvious from same figure that the short term aging after 2 and 4 hr was decreased the
Marshall flow by 8.82% and 14.7%, respectively. In the long term aging, the flow was also
decreased by 35.29 % and 38.23% for 3 and 5 days, respectively. This decrease might be
identified to that the aging make mixture stiffer than control mixture and good interlocking
between asphalt binder and particles of aggregate. The bulk density was decreased with time
of aging after short and long term aging. From Figure (5 - b), it is noted that the air voids were
increased after S.T.A (2 and 4 hr). In L.T.A, the air voids also increased. The voids in mineral
aggregate were increased after S.T.A and L.T.A. It indicates from same figure that the voids
filled with asphalt were decreased after short and long term aging. The decrease in the voids
filled with asphalt was due to the more voids (VTM) in the mixtures after exposure it to
aging.
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4.3. Effect of Replacement of Portland Cement by 50% of Silica Fume on The
Aging of Asphalt Mixture
Part of specimens was prepared and tested by replacing the Portland cement by silica fume as
mineral filler (50% Portland cement and 50% silica fume). Figure (6 - a) and (6 - b) show the
effect of this replacement on the aging of specimens. In the mixture that containing Portland
cement and silica fume together as mineral filler, the Marshall stability also increases with
time of aging but at a lower percent if compared with mixture that contained Portland cement
only. It is obvious that the Marshall flow was decreased with time of aging when using silica
fume with Portland cement together as mineral filler. The bulk density also decreased but at
lower percent if compared with mixture that contained Portland cement only. The use of silica
fume as a mineral filler together with Portland cement reduces the percent of voids in total
mixture by slightly percentages. The results showed that the use of 50 % silica fume as a
mineral filler with 50 % Portland cement leads to increase the V.M.A by slightly percentages.
V.F.A was reduced by slightly percentages when using of 50 % silica fume as mineral filler.
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Figure 3 Marshall Test Results for Specimens for 100 % Portland cement.
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Figure4 Marshall Test Results for Specimens for 50 % Portland cement and 50 % silica fume.
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Figure (5-a) Influence of Time of Aging on Properties of Marshall
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Figure (5-b) Influence of Time of Aging on Properties of Marshall
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Figure (6-a) Effect of Replacement of Portland cement by 50% of Silica Fume on The Aging of
Asphalt Mixture
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Figure (6-b) Effect of Replacement of Portland cement by 50% of Silica Fume on The Aging of
Asphalt Mixture.
5. CONCLUSIONS
•
Marshall Stability was increased by 13.63% and 27.27% after 2 and 4 hours, respectively.
•
Marshall Stability was increased by 51.81 % and 63.63%after 3 and 5 days, respectively.
•
In the short term aging, Marshall Flow was decreased by 8.82% and 14.7%after 2 and 4 hours,
respectively while in the long term aging, the flow was also decreased by 35.29 % and 38.23% for 3
and 5 days.
•
Bulk density was decreased with increasing time of aging.
•
Voids in total mixture were increased after short and long term aging.
•
Generally, the results showed that the using of 50 % silica fume as mineral filler with Portland cement
leads to change the influence of aging on properties of Marshall by different percentages.
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329–338.
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