RESEARCH ON APPLICATION OF REINFORCEMENTS
TO IMPROVE TENSE AND CRACKED RESISTANCE
OF ASPHALT CONCREAT
S Assoc. Prof. Dr. BUI XUAN CAY
P University of Communication and Transport, Vietnam
Abstract: This article represents initial results of the research to apply reinforced
asphalt concrete for improving tense and cracked resistance of this material, which is used as
bridge deck T and road pavement. This article will contribute to further researches in
Key word: Reinforced Asphalt.
I. INTRODUCTION R
Major reasons for cracking and skidding asphalt pavements are weak foundations;
spreading cracks from foundations consolidated with agglutinative inorganic substances or from
the old cement concrete foundations; horizontal forces; high braking forces at toll gates, and bus
stations; repeated loads; asphalts with low tense resistance; environmental conditions.
Especially, because of low tense resistance, phenomenon of cracks and skids in asphalt
pavements occurs very often.
In order to increase the tense resistance of asphalt concrete, some kinds of reinforcements
might be used. This article provides some initial results in researching reinforced asphalt
concrete, which might be shared for a discussion.
This study is conducted by Road and Highway Section at the University of Transport and
Communications combining with the Road Laboratory No.1 at the Institute of Science and
Technology for Transport and Communications.
II. INTERNATIONAL .
OVERVIEW ON THE STUDY
Reinforced asphalt concrete aiming at improving capability in bearing and cracking from
forces, which is used as the bridge deck slap or the wearing course of bus stations, has been
studied world-wide in many countries such as Germany, Holland, United States, Itali, etc., and
provided good results. ManyB companies that developed reinforcements for asphalt concrete can
be listed such as Maccaferri, Tensar, etc. Reinforcements, which are being applied include:
Steel reinforcement weaved in squares, in which steel diameter is 5 6 7.
Steel reinforcement weaved in meshes (Road mesh – Maccaferri).
Geotechnical reinforcement Tensar ARG.
The above reinforcements bring relatively high effects such as: reducing different kinds of
cracks, resisting the subsidence of wheel tracking, reducing the width of pavement, and
extending the lifetime of pavements.
III. EMPIRICAL STUDY IN LIBRATORY TO DETERMINE THE CRITICAL TENSE
RESISTANCE (RKU) OF REINFORCED ASPHALTS
In order to estimate the initial effects of reinforced asphalts, an empirical study has been
implemented in libratory to determine the critical tense resistance RKU of reinforced asphalts,
and to compare with the same asphalts without reinforcements. The asphalt concrete, which was
chosen for this empirical study is the dense asphalt concrete 10 (BTNC10), three
reinforcements, which are used includes geotechnical fibers without weaving, geotechnical
reinforcement meshes and steel reinforcement meshes.
3.1. Preparing materials of asphalt concrete and reinforcements
Material sources: stone gravels, stone powder, gold sand, and bitumen. Before mixing
to create specimens, bitumen and other materials must be tested to determine their criteria. The
contents and processes of the tests are carried out according to the Vietnamese standards 22TCN
279 - 01 and 22TCN 249 - 98.
Geotechnical fibers without weaving
Geotechnical reinforcement meshes Miragrid 5XT
Steel reinforcement meshes (diameter
Mould for creating specimens: a set including 3 moulds in the shape of beam with
dimensions of 4 x 4 x 16 cm are made of steel with the thickness of more than 20 mm.
Combination of specimens: with each type of bitumen, 6 specimens are tested to
determine the critical average tense resistance RKU.
Hydraulic compressor can compress with a force of 60 tons, and the pressure down to
the specimen is 300 daN/cm2.
Machine for testing the tense resistance must be satisfied with the following
The distance between two pillow-blocks (stable and dynamic pillow-block) must be
longer than 14 cm. The shape of pillow, which touches the specimen is cylinder with the radius
of 5 mm.
The plate for receiving force is made of metal in the shape of cylinder with the radius
of 10 mm, or of flat with the width of 8 mm. The loading speed of forces is 100 mm/minute.
3.2. Results of the test
The tense resistance RKU is determined according to the following formula:
Where: P - Load when the specimen is destroyed (daN); L - Distance between two beam
pillow-blocks (cm); b, h - width and height of the specimen (cm).
Some pictures of the test are presented in Figure 1.
a) Reinforcements b) Mould for creating specimens
c) Compressing specimens d) Specimen after compressed
e) Machine for testing the tense resistance f) Testing the tense resistance
Figure 1. Some pictures of the test in library
Results of the test are presented in table 1 and figure 2.
Table 1. Results for testing the tense resistance
of specimen Average load Average Rku
No Specimen (cm) height destroying subsidence in average
code width length (cm) specimen (mm) (daN/cm ) 2
(cm) (cm) (daN)
1 TM1 4 16 4.04 195.86 2.04 63.198
2 TM2 4 16 4.1 177.46 1.96 55.463
3 TM3 4 16 4.03 165.63 1.96 53.833
4 TM4 4 16 4.0 151.28 1.74 49.615
TM1 – Combination of asphalts with the steel reinforcement;
TM2 – Combination of asphalts with geotechnical fibers;
TM3 – Combination of asphalts with the geotechnical reinforcement;
TM4 – Combination of asphalts without reinforcements.
63,198 CT 2
ku in a g b× (da N/cm )
RRkutrunve age(daN/cm 2)
TM1 TM2 TM3 TM4
Tæ hîp mÉu
Combination of specimens
Figure 2. Diagram for comparing RKU between reinforced asphalts
and non - reinforced asphalt
IV. APPLICATION OF SOME REINFORCED ASPHALTS AT SOME LOCATIONS IN
4.1. Laying steel reinforcement meshes
In order to estimate the actual effects of some types of reinforcement to improve the
capability in bearing loads for asphalts, the research team selected three bus stations along the
route Thai Ha - Chua Boc for the test.
Regarding steel reinforcements, three meshes with diameter steel of 6 3 1 are
selected at three bus stations, respectively.
6 is laid at the bottom of the wearing course, with 7 cm thick;
3 is laid at the bottom of the 2-layer asphalt pavement, in which the wearing course is
3 cm thick, and the lower course is 5 cm thick;
1 is laid at the bottom of the wearing course, with 3 cm thick.
Table 2. Steel reinforcements
6 3 1
Dimensions of a mesh (cm) 15x15 6x6 2x2
Areas of reinforcement (m2) 18 9 24
Steps for construction
Cleaning the areas for laying the steel reinforcement meshes
Laying the steel reinforcement meshes
Stretching and locating the steel reinforcement meshes
CT 2 Sprinkling the tack coat
Laying asphalt concrete
Laying meshes Locating meshes
Sprinkling tack coat Laying asphalt concrete
Compacting Complete pavement
Figure 3. Some pictures at the constructional works No.3
(Chua Boc Street)
4.2. Testing with geotechnical reinforcement meshes
The research team used the reinforcement meshes Miragrid 5XT to test the pavement on
the approach of the bridge Dam – Tay Tuu – Tu Liem.
Steps for construction
Cleaning the area for laying the mesh Miragrid 5XT
Laying the meshes
Stretching and locating the meshes
Sprinkling tack coat
Laying asphalt concrete
Compacting CT 2
Laying and locating the geotechnical meshes Sprinkling tack coat
Laying asphalt concrete Compacting and completing pavement
Figure 4. Some figures during the construction on the approach of bridge Dam
4.3. Testing with geotechnical fibers
At some locations on roads inside the University of Transport and Communications Hanoi,
the research team also used some types of geotechnical fiber as be reinforcement laying at the
bottom of the 5-cm asphalt wearing course. Technology for construction is also similar to the
cases, which have been presented above. However, it must be ensured that the steps of
sprinkling tack coat, laying and compacting the geotechnical fiber are not rushed and waved.
4.4. Achieved results
After the construction from 5 to 6 months, according to the observation, the pavement
surface at the tested locations is better than other adjacent locations, which are not tested. The
research team is continuing to measure elastic module at the tested locations and non-tested
adjacent locations by using the Belkenman rod to compare the results.
V. CONCLUSIONS AND RECOMMENDATIONS
From the empirical study in library to determine the critical tense resistance (RKU) of
reinforced asphalt specimens, the research team recognized that the RKU value of reinforced
asphalt specimens is higher than RKU of non-reinforced asphalt. The detailed results are as
follows: RKU increases by 27.38 % when using the steel reinforced meshes, by 11.79 % when
using geotechnical fibers, by 8.49% when using the geotechnical reinforcement meshes.
The results also show that the adhesion between reinforcements and asphalt concrete
affects RKU significantly. When using normal asphalt concrete with high porosity, this
adhesion is low. In order to surmount this problem, the research team is also continuing to study
Mastic Asphalt, which is used in many countries with reinforcements.
The results did not reflect correctly in increasing the tense resistance between
specimens in library and in the site. Because the specimen in library is small, there are only two
fibers along the specimen when testing with geotechnical reinforcement meshes. In addition,
when testing with steel reinforcement meshes, the small steel diameters are used in library, but
bigger diameters are used in the site.
In order to increase the capability in bearing loads for the reinforced asphalt, the
following requirements must be ensured during the construction: reinforcements must be
stretched and located at the lower layer, the tack coat must be sprinkled carefully.
Through the tests in the site, at first, it is roughly seen that asphalt concretes with steel
reinforcement meshes is as good as those without steel reinforcement meshes. However, in
order to estimate the capability of asphalt concrete in bearing loads as well as its durability, it is
necessary to measure and compare in a period of time.
5.2. Limitations and recommendations
Because of the high tense resistance of reinforcements, this issue should be
significantly interested to continue studying for a spread application for asphalt concretes,
especially at the permanently high load locations such as bus stations, toll gates, traffic signals,
approach to bridge, bridge deck slap, and runways in the airport.
theoretical methodology to calculate the reinforced asphalt pavements must be developed to
reduce the width of reinforced asphalt concrete.
Checking the tense resistance of reinforced asphalts must be developed.
In order to increase the adhesion between reinforcements and asphalt concrete and to
ensure mutual works of these two materials, Mastic Asphalt should be studied.
Due to the time and conditions of the study is limited, the research team has not given
out the detailed estimations to quantify in technical and economical for a comparison with other
In order to continue the study, budget and supports from the Ministry of Transport,
and co-operation among colleagues are needed.
Applying the geotechnical reinforcement meshes has an advantage that the
maintenance and removability of the asphalt concrete can be implemented easily.
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