JOURNAL OF ENGINEERING RESEARCH AND TECHNOLOGY, VOLUME 3, ISSUE 4, DECEMBER. 2016 

  
 

85 

 

Study of the Mechanical and Physical Properties of Self -healing Asphalt  

Shafik Jendia
1
, Noor Hassan

2
, Khadija Ramlawi

2
, Hadeel Abu-Aisha

2
 

1
 Professor of Highway Engineering, Islamic University of Gaza, Palestine 

2
 Faculty of Engineering, Islamic University of Gaza, Palestine 

 

Abstract— Asphalt Pavement needs continuous maintenance to fulfill the required level of performance. This research aims to study the 

effect of adding steel wool (SW) on the property of the self-healing of the wearing layer in the asphalt mix. Several Tests have been conducted 

on aggregates, SW and bitumen to evaluate their properties. Asphalt mixes have been prepared in accordance with standard specifications 

followed by testing asphalt samples to obtain values of the stability, flow and specific gravity  . Marshall Method has been used for the design of 

the asphalt mix to determine the optimum content of SW as well as to obtain the characteristics of SW modified asphalt mixture. 20 samples 

were prepared to determine the optimum SW content and to investigate the self-healing property through various tests. Asphalt samples with 

SW content of 5% showed the best thermal and electrical conductivity. The results showed also that it is possible to use SW in the preparation 

of asphalt wearing layers to enhance the self-healing property by heat induction. Asphalt samples with SW content of 3 and 5 % presented the 

strongest bonding among the different percentages. Accordingly, Marshall samples test results showed that the optimal content of SW is 4.33% 

(by volume of optimum bitumen content).  

 
Index Terms— Self-Healing Asphalt, Steel Wool, Heat Induction.   

 

1     INTRODUCTION 

 Asphalt pavement consists  of several layers: asphalt layers 

(mainly binder and wearing courses)  and base layers (mainly 

base and sub base courses) constructed  on a subgrade with 

a suitable bearing capacity.  An asphalt layer consists of 

mineral aggregates, asphalt binder (bitumen)  and air voids. 

The pavement  behavior under traffic and climatic loads 

depends on many mechanisms that are strongly related to the 

load transfer between layers and aggregate particles in each 

layer. The increase of dynamic load (traffic)  in combination 

with neglecting preventive maintenance cause an accelerated 

and continuous deterioration of the road network. To 

overcome   this problem, a pavement management system is 

effective and strongly needed to control the pavement 

condition during its analysis or performance period.  

 

Asphalt pavement performance is affected by several factors, 

e.g., the properties of the components (binder, aggregate and 

additive) and the proportion of these components in the mix. 

The performance of asphalt mixtures can be improved with 

the utilization of various types of additives, these additives 

include: polymers, latex, steel wool and many other additives 

[1].  

 

Induction heating of asphalt concrete is a technique that 

consists of heating electrically conductive particles, for 

example, steel wool fibers, previously mixed into the asphalt 

concrete mixture. Then, with the help of an induction heating 

device, it is possible to heat the particles locally and, through 

heat diffusion, heat the binder and heal the cracks. It was 

illustrated in [2]  that a very small volume of fibers, more than 

0%, serves to increase the temperature via induction heating. 

 

The first prerequisite of induction heating is that the heated 

material must be conductive. The second prerequisite is that 

these fillers and fibers are connected in closed-loop circuits. 

First a micro crack appears in the bitumen. If enough volume 

of conductive fibers or fillers is added they will form closed-

loops circuits all around the micro crack. If this magnetically 

susceptible and electrically conductive material is placed in 

the vicinity of a coil, eddy currents are induced in the closed-

loops circuits, with the same frequency of the magnetic field. 

Heat is generated through the energy lost when eddy currents 

meet with the resistance of the material and, finally, bitumen 

is melted and the crack is closed [3]. 

 

In this research the possibility of using conductive materials, 

such as steel wool (SW), to produce self-healing asphalt is 

investigated. The principle objectives of this research are to:  

 Study the effect of adding different percentages of local 

SW on the self-healing mechanism of asphalt mix. 

 Compare it with conventional mix properties. 

 Identify the optimum percent of SW to be added in the 

HMAs. 

2     MATERIALS and Test Procedures 

2.1 Materials and Laboratory Tests 

Bitumen: The laboratory tests performed to evaluate the 

bitumen properties are: specific gravity, ductility, flash point, 

penetration and softening point. The properties of asphalt 

binder are presented in Table (1) and compared with ASTM 

specification limits. 

Steel Wool material: Steel Wool was obtained from a local 

market (kitchen wash steel wool) then chopped manually. 

Properties of used steel wool material are shown in Table (2). 

In order to define the properties of used aggregates, number 

of laboratory tests have been conducted, these tests are: 

a. Sieve Analysis( ASTM C 136) 

b. Specific gravity test (ASTM C127). 

c. Water absorption (ASTM C128) 

d. Los Angles abrasion (ASTM  C131) 

 

 

 

 

 

 

http://en.wikipedia.org/wiki/Construction_aggregate
http://en.wikipedia.org/wiki/Asphalt


SHAFIK JENDIA, NOOR HASSAN, KHADIJA RAMLAWI, HADEEL ABU-AISHA/ STUDY OF THE MECHANICAL AND PHYSICAL... (2016) 

86 

 

Table 1: Summary of bitumen properties 

Test Specification Results 

ASTM 

Specification 

Limits 

Penetration 

(0.01 mm) 
ASTM D5-06 65 60-70 

Ductility (cm) 
ASTM D113-

86 
146 Min 100 

Softening point 

(
o
C) 

ASTM D36-

2002 
50 (48 – 56) 

Flash point 

(
o
C) Open Cup 

© 

ASTM D92-02 308 Min 230
o
 C 

Solubility (%) ASTM D2042   

Specific 

gravity (g/cm
3
) 

ASTMD D70 1.05 1.01-1.06 

Table 2: Steel Wool properties 

Property Detail 

Diameter (µm) 97.54 

Length (mm) 3.0 - 7.0 

Density (g/cm
3
) 6.61 

 

Aggregates: The coarse and fine aggregates used were 

crushed rocks imported from Egypt. Aggregates used in 

asphalt mix can be divided as shown in Table (3). 

Table 3: Aggregates types 

Type of aggregate  
Particle size 

(Gradation) (mm) 

Adasia 0/ 12.5 

Simsimia 0/ 9.50 

Trabiah 0/4.75 

Table (4) presents the gradation of proposed mix and Table 

(5) presents the results of aggregates tests 

2.2 Methods 

2.2.1 Obtaining the Optimum Bitumen Content (OBC)  

Marshall Method for designing hot asphalt mixtures is used to 

determine the OBC. A previously prepared gradation and 

obtained OBC are used from reference [2].  However in this 

research, 20 samples of a weight of 1230 g were prepared 

with four different steel wool content (SWC: 0, 3, 5 and 

7%).and compacted with 75 blows according to standard 

Marshal design method designated in ASTM D 1559 [4]. Five 

samples were prepared from each SW percentage; three 

samples from each SWC were used to perform Marshal 

Stability [5], bulk density [6] and Theoretical Maximum 

Specific Gravity tests [7]. 

Table 4: Gradation of proposed mix with ASTM Specifications 

limits 

Sieve size (mm) % Passing 

19.5 100 

12.5 90 

9.5 75 

4.75 55 

2.36 37 

1.18 23 

0.60 13 

0.30 8 

0.15 6 

0.075 4 

Table 5: Results of aggregates tests 

Test 
Eff. Specific Gravity 

(g/cm
3
) 

Absorption (%) 

Adasia 

0/ 12.5 
2.67 1.8 

Simsimia 

0/ 9.50 
2.595 3.39 

Trabia 

0/4.75 
2.59 3.36 

Designation 

Number 
ASTM : C127 ASTM : C128 

Specification limits -- < 5 

 

2.2.2 Preparation of asphalt mix with different steel wool 

content 

There was no specific procedure for mixing the SW with the 

aggregate and bitumen therefore initial experimental trials 

were conducted to achieve the most applicable process of 

addition.  In this study; the aim of adding SW to asphalt mix is 

to investigate the ability of self-healing in asphalt and not to 

enhance the strength of asphalt mix. After blending the 

aggregate with the previously obtained OBC (5.6%), the 20 

samples were prepared to evaluate the effect of adding SW to 

asphalt mixture samples by considering four proportions of 

SW (0.0, 3.0, 5.0 and 7.0% by the volume of bitumen).  
The procedure of incorporating SW in asphalt mix can be 

summarized as follows: 

a) SW have to be chopped by scissors to achieve the 

required length range (2.0 – 7.0) mm.  

b) Aggregates (Adasia (0/12.5), Simsimia (0/9.5), Tirabeya 

(0/4.75) are heated for 24 hours at 150
o
C to obtain 

completely dry condition. 

c) Requisite amount of bitumen is heated for 4 hours at a 

temperature of 150
o
C. 

d) Aggregates are mixed together followed by addition of 

hot bitumen at OBC. 

e) Requisite amount of chopped SW is thrown gently on the 

mix and over several batches with continuous mixing. It 

should be taken in consideration to mix uniformly in 

order to prevent forming clusters of SW. 

f) All ingredients are mixed vigorously to form a 

homogeneous asphalt mixture.  

g) After preparing modified asphalt mix, specimens are 

prepared, compacted with 75 blows, and tested 

according to standard Marshal Method (ASTM D 1559 

[6]).  

2.2.3 Evaluation of self-healing mechanism in asphalt 
To perform these tests properly, the compacted specimen’s 

samples were cut into thinner cylindrical samples with 
thickness of 20 mm and a diameter of 101.6 mm, this is done 

to obtain flat surfaces which allow good contact between 



SHAFIK JENDIA, NOOR HASSAN, KHADIJA RAMLAWI, HADEEL ABU-AISHA/ STUDY OF THE MECHANICAL AND PHYSICAL... (2016) 

87 

 

different elements of the test instruments and the surface of 

the sample. After cutting, the samples were placed in an oven 

at 40 ºC for 2 hours to remove the moisture which was coated 

during the cutting process and prevent the SW from corroding 

on the surface of the samples. Inside the sample, the SW do 

not corrode, because they are completely coated with 

bitumen [8]. 

Electrical resistivity measurements test 

To study the electrical conductivity of asphalt mixes, their 

electrical resistance was measured in experiments at a room 

temperature of 22.4 ºC. A Fluke digital multimeter was used 

to measure the resistance below 36×106Ω. Accordingly, two 

aluminum plates electrodes connected with the multimeter 

were placed at both ends of the sample to measure its 

resistance. A small pressure was applied to the copper 

electrodes to obtain a good contact with the surface of the 

sample. 

After measuring the resistance, the electrical resistivity of 

each sample was obtained from the second Ohm-law 

equation as follows: 

   
  

 
   ……………………………………………..……… (1) 

Whereas, 

  = The electrical resistivity, [Ω m]. 

R= the measured resistance, [Ω]. 

S= the electrode conductive area, [m
2
]. 

L = the thickness of the cylinder, [m]. 

 

Heat transmission measurements test 

Hot plate was used to study heat transmission through a 20 

mm thic  asphalt samples with different S C (0.0, 3.0, 5.0 

and 7.0 ). Temperature of hot plate was set to 70  c and a 

laser thermometer was used to measure the temperature at 

the top and bottom surface of the samples at a five minutes 

interval for 30 minutes. Room temperature was recorded to 

be 22.4  C (the asphalt samples initial temperature).  

Healing of full cracked asphalt samples using microwave 

Asphalt samples with different SW contents (0.0, 3.0, 5.0 and 

7.0 ) were cut to a thic ness of 20mm and frozen at a 

temperature of -17.5  C for 48 hours in order to ensure 

homogenous hardening of the sample that facilitates the 

breaking process. Then a spontaneous full crack was 

introduced to the sample by a hammer in order to investigate 

the healing tendency of each sample. Samples were then put 

in a microwave with a power of 700 Watt for two stages. 

Firstly, samples were heated in the microwave for 60 seconds 

and then their temperatures were measured using a digital 

thermometer. Secondly, samples were put in the microwave 

for 90 seconds and their temperatures were also recorded, 

after that, the samples were immediately put back in their 

molds until they cool down. Twenty-four hours later, they 

were extracted from the molds and visually inspected to 

determine which samples have a better healing tendency. 

3     RESULT ANALYSIS 

The effect of adding different SW percentages on the 

properties of asphalt mix are analyzed and compared with the 

conventional asphalt mix (No additive) properties, which acts 

as the control group. These properties include Marshal 

Stability, flow, bulk density, Air voids (Va) and Voids in 

mineral aggregates (VMA) in addition to other tests to 

evaluate the self-healing property of asphalt. 

3.1 Mechanical Tests 

3.1.1 Stability – SW content relationship 

The stability of modified asphalt mixes oscillates. First, the 

addition of SW more than 0% (by volume of bitumen) reduces 

the stability by approximately 27% at a SWC of 3%, then it 

starts increasing until it reaches a maximum of 1950.10 kg at 

a SWC of 5% which is very close to the stability of 

conventional asphalt mix. The curve then start falling again 

until a SWC of 7%. Figure (1) shows the oscillation of the 

stability of modified asphalt mix with a maximum stability at a 

SWC of 5%. 

 

 

Figure 1: Asphalt mix Stability – SW content relationship. 

 

The noticeable drop in stability at first is attributable to the 

replacement of aggregate with a small amount of SW until it 

reaches a minimum stability of 1441.30 at 3% volume of SW. 

After that any additional replacement of aggregate increase 

the stability of the mix until it reaches a maximum value at 5% 

SW volume. Again the stability starts decreasing due to large 

amount of aggregate being replaced by SW that does not 

provide the same stability aggregate does. The decrease in 

stability can also be explained by the nesting of SW around 

the aggregate that occurred during mixing which led to slight 

loss of bonding between the contents of the mixture. 

 

3.1.2 Flow – SW content relationship 

Generally, the flow of modified asphalt mix is higher than the 

conventional asphalt mix (2.47 mm). Figure (2) shows that the 

flow increases continuously as the SWC increases. The flow 

value extends until it reaches (3.88mm) at SWC of 7%. 

 

Figure 2: Asphalt mix flow – SW content relationship. 

 

 

0

500

1000

1500

2000

2500

0 2 4 6 8
S

ta
b

il
it

y
(K

N
) 

% of steel by volume of bitumen 

0

1

2

3

4

5

0 2 4 6 8

F
lo

w
(m

m
) 

% of steel wool  by volume of bitumen 



SHAFIK JENDIA, NOOR HASSAN, KHADIJA RAMLAWI, HADEEL ABU-AISHA/ STUDY OF THE MECHANICAL AND PHYSICAL... (2016) 

88 

 

3.1  Bulk density – SW content relationship 

The bulk density of compacted SW modified asphalt mixture 

is lower than the conventional asphalt mix (2.367 g/cm
3
). The 

general trend shows that the bulk density decreases as the 

SWC increases. The maximum bulk density is (2.30 g/cm
3
) at 

SWC (3.0 and 5.0%) and the minimum bulk density is (2.27 

g/cm
3
) at SW (7%). This decrease of bulk density can be 

explained to be as a result of increasing percentage of void 

as the SWC increases. 

 Figure (3) shows asphalt mix bulk density – SWC 

relationship 

 

Figure 3: Asphalt mix bulk density – SW content relationship. 

3.2   Air voids (Va) – SW content relationship 

In general, the air voids proportion of modified asphalt mixes 

is higher than conventional asphalt mix (3.82 %). Va % of 

modified asphalt mixes increases gradually as the SW 

content increase till it reaches the highest Va% value at 7% 

SWC. Generally modified asphalt mixes have Va% content 

exceeding the specifications range due to the mentioned 

nesting problem that indicates a higher compaction energy is 

required for modified asphalt mixes with SW. Figure (4) 

shows the curve which represents asphalt mix air voids – 

SWC relationship. 

 

Figure 4: Asphalt mix air voids (Va %) – SW content relationship. 

3.3  Voids in mineral aggregates (VMA) – SW content 

relationship  

The voids in mineral aggregates percentage VMA% for 

asphalt mix is affected by air voids in asphalt mix Va and 

voids filled with bitumen Vb. VMA% of modified asphalt mixes 

is generally higher than conventional asphalt mix (16.44%). 

VMA % of modified asphalt mixes is approximately constant 

(20.94% at 7% of SW content). Even though Va % increases 

as the SW content increases, VMA remains the same due to 

decrease of bulk density which decreases Vb as well .Figure 

(5) shows the curve which represents asphalt mix VMA% – 

SWC relationship. 

 

Figure 5: Asphalt mix voids of mineral aggregates (VMA) – 

SW content relationship. 

3.4 Optimum steel wool  (modifier) content 

A set of controls is recommended in order to obtain the 

optimum modifier (SW) content that produces an asphalt mix 

with the best mechanical properties [9, 10]. Asphalt mix with 

optimum modifier content satisfies the following: 

 Maximum stability 

 Maximum bulk density 

 Va % within the allowed range of specifications. 

Figures (1, 3 and 4) are utilized to find SW percentages which 

satisfy these three controls. The SW percentages which 

satisfy controls are summarized in Table (6). 

 The Optimum SW content is the average of the 

previous three SW contents. 

 Optimum SW content (By OBC weight) = 4.33 %. 

 

 

Table 6: Summary of controls to obtain optimum modifier 

content 

Property SW  ( By OBC volume) 

Maximum stability 5 % 

Maximum bulk density 5 % 

Va % within the allowed range 

of specifications 
3 % 

3.5 Comparison of control mix with SW modified mix  

A comparison of the mechanical properties of SW modified 

asphalt mix at the optimum SWC (4.33 % by OBC volume) 

and properties of the conventional (control) asphalt mix is 

shown in Table (7). Minimum and maximum allowed limits are 

also presented according to Municipality of Gaza 

specifications in Table (8) [11].  

2.26

2.28

2.3

2.32

2.34

2.36

2.38

0 2 4 6 8

B
u

lk
  

d
e

sn
si

ty
 (

g
/m

3
) 

% of steel wool by volume of bitumen 

0

2

4

6

8

10

0 2 4 6 8

A
ir

 v
o
id

 %
 

% of steel wool by volume of bitumen 

0

5

10

15

20

25

0 2 4 6 8

V
M

A
[%

] 

%  of steel wool by volume of bitumen 



SHAFIK JENDIA, NOOR HASSAN, KHADIJA RAMLAWI, HADEEL ABU-AISHA/ STUDY OF THE MECHANICAL AND PHYSICAL... (2016) 

89 

 

 

Table 8: Properties of SW modified asphalt mix with 

specifications range 

 
It is clearly shown that asphalt mix modified with (4.33% SWC 

by OBC volume) has a slightly lower stability and stiffness 

compared to the conventional asphalt mix, but still higher than 

the specified minimum range. While for the other properties of 

modified mix are within the range except for air void that is 

slightly out of the allowed range of the specifications. This can 

be improved by performing a special mixing procedure that 

guarantees a better homogeneity of the mixture. 

3.6 Self-healing mechanism tests 

Several tests were conducted to obtain the phenomena of 

self-healing of asphalt samples with different SWC (0.0, 3.0, 

5.0 and 7.0% by OBC volume). These tests include: electrical 

resistivity measurements, heat transmission measurements 

and healing of cracked asphalt samples using microwave.  

3.6.1 Electrical resistivity measurement test 

The resistivity of conventional and modified asphalt mix 

samples were measured using fluke digital multimeter, Figure 

(6) shows the relationship between electrical resistivity and 

SWC in asphalt mix. 

 

 

Figure (6): Asphalt mix electrical resistivity – SWC 

relationship. 

The Figure shows that an amount of SW=0, the electrical 

resistivity is very high, it is exhibiting the case of insulating 

behavior. The addition of more SW to the mix decreases the 

electrical resistivity. The SWC (3 – 5%) can be considered 

as the optimal content for conductivity purpose, because 

adding more steel wool above this content to the mixture 

improve its electrical conductivity weakly. 

3.4.2 Heat transmission measurement test 

The test was performed to investigate heat transmission 

through the samples using hot plate. Figure (7) shows for 

example the temperature change in asphalt sample at SWC 

of 5% with time at top and bottom surface. 

Figures (8) and (9) illustrate how the temperature changes 

over a period of time of 30 minutes on top and bottom 

surfaces for asphalt samples with different SWC. Samples 

with SWC of 3% and 5% exhibits the highest heat 

transmission between top and bottom surfaces of samples 

among the four percentages of SWCs. Although asphalt 

samples with SWC of 7% has the highest electrical 

conductivity, it exhibits the lowest heat transmission. Figure 

(10) summarizes the heat transmission rate for asphalt 

samples with different SWC at bottom surfaces after five 

minutes. 

 

0.00

0.10

10.00

1000.00

100000.00

10000000.00

0 2 4 6 8

E
le

ct
ri

ca
l 

R
e

si
st

iv
it

y 
(1

0
3
 Ω

m
) 

% of steel wool by volume bitumen 

0

10

20

30

40

50

60

70

0 10 20 30 40

T
e

m
p

e
ra

tu
re

 (
C̊

) 

Time (minutes) 
Top surface Bottom surface

Table 7: Comparison of SW modified asphalt mix and 

conventional (control) mix properties 

Property 
Conventional  

asphalt mix 

(4.33%) SW 

modified 

asphalt mix 

(By OBC 

volume  ) 

Change 

amount 

OBC (%) 5.60 5.60 - 

Stability (kg) 1973.49 1811.67 - 8.20 % 

Flow (mm) 2.47 3.65 + 47.77% 

Stiffness 

(kg/mm) 

798.98 492.60 - 37.22% 

VMA % 16.42 19.43 +18.33 % 

Va% 3.80 7.17 + 

88.68 % 

Bulk density 

(gm/cm3) 

2.367 2.30 - 2.83 % 

Property (4.33%) SW 

modified asphalt 

mix (By OBC 

volume) 

Local Spec. 

(MOG, 1998) 

[11] 

Min. Max. 

Stability (kg) 1811.67 900 * 

Flow (mm) 3.65 2.0 4.0 

VMA% 19.43 13.5 * 

Va% 7.17 3.0 7.0 

Bulk density 

(g/cm3) 

2.30 2.30 * 



SHAFIK JENDIA, NOOR HASSAN, KHADIJA RAMLAWI, HADEEL ABU-AISHA/ STUDY OF THE MECHANICAL AND PHYSICAL... (2016) 

90 

 

Figure (7): Relationship between top and bottom surface 

temperatures with time at SWC of 5% (by OBC volume). 

 

Figure (8) Relationship between bottom surface temperatures 

with time and different SWC. 

 

Figure (9) Comparison between top surface temperatures 

with time and different SWC. 

Careful consideration to Figure (10) shows a significant 

results of heat transmission for asphalt samples with different 

SWC. For example, considering the heat transmission after 

five minutes indicates a higher heat transmission rate for 

asphalt samples with SWC of 3% and 5% (105% and 111% 

respectively) and a slow rate for conventional asphalt 

samples (SWC = 0%) which integrates with the previously 

mentioned concept of electrical resistivity of asphalt samples 

with different SWC. 
 

 

Figure (10) Heat transmission rate after five minutes at the 

bottom surface of asphalt samples. 

The specified optimum SWC (4.33% by OBC volume) lies 

within the range of SWC that provides the highest heat 

transmission rate. Further analysis of the figure shows that an 

increase in SWC greater than the optimum SWC range 

doesn't provide a higher heat transmission rate. On the 

contrary, asphalt samples with SWC of 7% has a reduced 

efficacy by 5% compared to asphalt samples with 0% SW 

content which is referred to the inhomogeneity of mix that 

forms clusters which do not provide a homogenous 

distribution of heat through its surface instead it provides a 

local heating where clusters occur.  

3.4.3 Healing of cracked asphalt samples using 

microwave 

Testing procedures were performed and results were 

recorded. Table (9) shows the temperature of asphalt 

samples with different SWC after 60 and 90 second of being 

heated at the microwave. 

Table (9): Temperature of asphalt samples after 60 and 90 

seconds in microwave. 

SW content (% 

by OBC volume) 

                        ) 

for 60 seconds for 90 seconds 

0 24 31.5 

3 60 80 

5 55 75 

7 50 70 

 

In reference to the table, heating samples with different SWC 

exhibits different behavior of microwave heat absorption for 

each time interval. It was observed that the same pattern of 

heat and electrical resistivity is followed for microwave 

heating. Samples with 3% SWC has the highest temperature 

after being heated in the microwave for 60 and 90 seconds, 

while temperature of samples with SWC = 0% was around 

room temperature after 60 seconds which clearly shows the 

inefficacy of conventional asphalt mix when introducing heat 

for self-healing purposes. Whereas, samples with SWC of 7% 

exhibits a good microwave heat absorption but a partial 

damage to the sample was observed after heating to 90 

seconds due to low stability and inhomogeneity of the 

sample. Visual inspection of samples after 24 hours of being 

left to cool down to room temperature in molds where it was 

originally casted. Samples with SW content of 3 and 5% were 

seen to have an excellent bonding between the fractured 

surfaces, whereas the 7% SW sample did not have an 

efficient healing. 
Figure (11) shows the relationship between SWC and the 

dramatic decrease in electrical resistivity while air void 

percentage increases gradually. 

0

10

20

30

40

50

60

70

0 10 20 30 40

T
e

m
p

e
ra

tu
re

 (
C

)̊ 
 

Time(minutes) 
 0% SW 3% SW 5% SW 7% SW

30

35

40

45

50

55

60

65

70

0 10 20 30 40

T
e

m
p

e
ra

tu
re

 (
C

)̊ 

Time (minutes) 
3% SW 5% SW 7% SW 0% SW

0

20

40

60

80

100

120

0 2 4 6 8

H
e

a
t 

tr
a

n
sm

is
si

o
n

 r
a

te
(%

) 

% of steel wool by volume of bitumen 



SHAFIK JENDIA, NOOR HASSAN, KHADIJA RAMLAWI, HADEEL ABU-AISHA/ STUDY OF THE MECHANICAL AND PHYSICAL... (2016) 

91 

 

 

Figure (11): Relationships between SWC, electrical resistivity 

and air void ratio. 

 

4     CONCLUSIONS 

Based on experimental work results for SW modified asphalt 

mixtures compared with conventional asphalt mixtures, the 

following conclusions can be drawn: 

a) The optimum amount of SW to be added as a 

modifier of asphalt mix was found to be (4.33%) by 

volume of OBC of the asphalt mix. 

b) higher compaction energy is required for modified 

asphalt mixes with SW to obtain higher values of 

bulk density and reduce air void percentage to be 

within the specified range 

c) Asphalt mix with SW needs more time in mixing 

compared with the conventional asphalt concrete 

mix due to its special mixing process whereas SW 

is added to the mixture of aggregate and bitumen 

by throwing chopped SW into the mix gently over 

several batches during continuous mixing. 

d) Asphalt mix modified with SW exhibits higher flow 

values as the SW percentage increased.  

e) Asphalt samples with SW content of 3 and 5% 

represent the best healing behavior compared with 

samples with 7% SW content. 

f) Adding SW to the asphalt mix greater than the 

optimal content causes nesting (clusters) in the 

mixture, which reduces the stability of mix due to 

the higher air void percentage. 

g) Adding steel wool to asphalt mix makes it 

electrically conductive. The electrical resistance of 

asphalt concrete depends on the content of SW. 

There is an optimal content of SW to obtain the 

highest conductivity. Greater than this optimal 

content, addition of more steel SW does not 

increase the conductivity anymore. Excess SW can 

make the mixture difficult to mix. 

h)  Asphalt concrete with steel wool can be heated 

with induction energy. Content of the SW are 

important for the heating speed of asphalt concrete. 

There is an optimal content of steel wool. Addition 

of SW above the optimum does not increase the 

induction heating speed anymore. 

i) The durability of asphalt concrete roads will be 

improved with induction heating due to the 

improvements in the healing capacity. 

 

 

 

 

5     REFERENCES 

[1] Awwad, M & Shabeeb, L. “The use of Polyethylene in 

hot asphalt mixtures”, American Journal of Applied 

Sciences, 2007, pp. 390-396. 

[2] García A., Bueno M., Norambuena-Contreras J. and 

Partl M., “Induction healing of dense asphalt concrete”, 

Switzerland, 2013.  

[3] Schlangen E., “ Addressing Infrastructure Durability and 

Sustainability by Self-Healing Mechanisms - Recent 

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paper presented to the 2nd International Conference on 

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2013. 

[4] ASTM D 1559, “Standard Test Method for Marshal Test”, 

American Society for Testing and Materials, West 

Conshohocken, 2002. 

[5] ASTM, 2004.  “Test Method for Resistance to Plastic 

Flow of Bituminous Mixtures Using Marshall Apparatus”, 

American Society for Testing and Materials, West 

Conshohocken, 2004. 

[6]   ASTM D 2726, “Test Method for Bul  Specific Gravity 

and Density of Compacted Bituminous Mixtures Using 

Saturated Surface-Dry Specimens”, Philadelphia, US, 

1992. 

[7] ASTM D 2041, “Test Method for Theoretical Maximum 

Specific Gravity and Density of Bituminous Paving 

Mixtures”, Philadelphia, US, 1992.  

[8] Liu, Q., “Induction Healing of Porous Asphalt 

Concrete”, PhD-thesis Delft University of Technology, 

The Netherlands, 2012. 

[9] Jendia, S., “Highway Engineering: Structural Design. 

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Palestine, 2000, pp. 63-68. (Arabic reference). 

[10] Jendia, S. El-Sai aly, M., “Study of the Possibility to 

Reuse Waste Plastic Bags as a Modifier for Asphalt 

Mixtures Properties (Binder Course Layer)”. The 11
th
 

Global Conference on Sustainable Manufacturing. 22-25 

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[11] Municipally of Gaza (MOG), “General and Special 

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and development of projects administration- Municipally 

of Gaza, Gaza strip, Palestine, 1998. ( Arabic reference) 

 

 

 

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http://www.sciencedirect.com/science/article/pii/S1877705813003597