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OF ASPHALT CONCREAT Assoc Prof Dr BUI XUAN CAY Unive RESEARCH

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OF ASPHALT CONCREAT Assoc Prof Dr BUI XUAN CAY Unive RESEARCH Powered By Docstoc
					      RESEARCH ON APPLICATION OF REINFORCEMENTS
                 O
         TO IMPROVE TENSE AND CRACKED RESISTANCE
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                                OF ASPHALT CONCREAT
                 A
                 S                             Assoc. Prof. Dr. BUI XUAN CAY
                 P                             University of Communication and Transport, Vietnam
                 H
                 A
         Abstract: This article represents initial results of the research to apply reinforced
                 L
    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
                 slap
    Vietnam.
         Key word: Reinforced Asphalt.
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                 O
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                 C
I. INTRODUCTION  R
                 E
      Major reasons for cracking and skidding asphalt pavements are weak foundations;
                 A
spreading cracks from foundations consolidated with agglutinative inorganic substances or from
                 T
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.
                               A
    In order to increase the tense resistance of asphalt concrete, some kinds of reinforcements
                               s
                               s
might be used. This article provides some initial results in researching reinforced asphalt
                               o
concrete, which might be shared for a discussion.
                               c
                               .
    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
                           P
                           r
Technology for Transport and Communications.
                            o
                            f
II. INTERNATIONAL           .
                            OVERVIEW         ON THE STUDY
     Reinforced asphalt concrete aiming at improving capability in bearing and cracking from
                             D
                             r
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
                             U
be listed such as Maccaferri, Tensar, etc. Reinforcements, which are being applied include:
                             I
         Steel reinforcement weaved in squares, in which steel diameter is         5   6    7.
                           X
         Steel reinforcement weaved in meshes (Road mesh – Maccaferri).
                           U
                           A
                           N

                             C
                             A
                             Y

                             U
                             n
                             i
                             v
                             e
         Geotechnical reinforcement Tensar ARG.
         Geotechnical reinforcement.
    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.
         Reinforcements:
         Geotechnical fibers without weaving
         Geotechnical reinforcement meshes Miragrid 5XT
                                                                                                   CT 2

         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
requirements:
         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:

                                                                       3.P.L
                                                          R        =
                                                              KU       2.b.h
                                                                            2



           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


CT 2




                    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

                                   Average  Dimensions
              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.


                                70,000
                                                 63,198                                                                              CT 2
      ku in a g b× (da N/cm )
     RRkutrunve age(daN/cm 2)




                                60,000
                           2




                                                                     55,463
                                                                                          53,833
                                                                                                               49,615
                                50,000
                r nh




                                40,000

                                30,000

                                20,000

                                10,000

                                   -
                                                 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
HANOI
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

         Steel type
                                                          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
                 Compacting




                            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
       5.1. Conclusions
                 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.
CT 2
                 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
solutions.
           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.




             Reference
[1]. Bộ Giao thông Vận tải, 2001. Tiêu chuẩn ngành 22TCN 279 - 01, Quy trình thí nghiệm bê tông nhựa.
             NXB Giao thông Vận tải, Hà nội.
[2]. Bộ Giao thông Vận tải, 1998. Tiêu chuẩn ngành 22TCN 249 - 98, Quy trình kỹ thuật thi
công và nghiệm thu mặt đường bê tông nhựa. NXB Giao thông Vận tải, Hà nội.
[3]. ThS. Nguyễn Quang Phúc, Vật liệu Mastic Asphalt ở Anh, tạp chí KHGTVT – Trường Đại
học Giao
thông Vận tải, số 12 tháng 11 năm 2005.
[4]. Maccaferri, AMIA and AST, 1998. Appication of the road mesh as pavement reinforcement
in a bus
stop area Palermo. Italy.
[5]. Maccaferri, AMIA and AST, 2000. Road works problems and solutions asphalt
pavement
reinforcement. Italy.
[6]. Tensar internationnal, 2006. Asphalt pavements reinforcing asphalt layers in roads and trafficked
areas. England.
[7]. Saint - Gobail, 2002. Technical manual, advanced fiber glass technology for asphalt
pavement
overlays. Canadian.
[8]. Swedish National Road and Transport Research Institute, Investigation of material specification

of steel and configuration of steel fabric – Final report T2-02, 2002

				
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