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IMPROVING IMPACT AND MECHANICAL PROPERTIES OF GAP-GRADED CONCRETE

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IMPROVING IMPACT AND MECHANICAL PROPERTIES OF GAP-GRADED CONCRETE Powered By Docstoc
					  International Journal of Civil Engineering OF CIVIL ENGINEERING AND
  INTERNATIONAL JOURNAL and Technology (IJCIET), ISSN 0976 – 6308
  (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME
                            TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 4, Issue 2, March - April (2013), pp. 118-131
                                                                           IJCIET
© IAEME: www.iaeme.com/ijciet.asp
Journal Impact Factor (2013): 5.3277 (Calculated by GISI)                © IAEME
www.jifactor.com




    IMPROVING IMPACT AND MECHANICAL PROPERTIES OF GAP-
      GRADED CONCRETE BY ADDING WASTE PLASTIC FIBERS

                        Dr. Abdulkader Ismail Abdulwahab Al-Hadithi
           Assist. Prof. -College of Eng. / University of Anbar /Ramadi, Al-Anbar, Iraq.



   ABSTRACT

           This research includes the study of the effect of adding the chips resulting from
   cutting the plastic beverage bottles by hand (which is used in Iraqi markets now) as small
   fibers added to the gap-graded concrete. These fibres were added with different percentages
   of concrete volumes. These percentages were (0.5%) , (1%) and (1.5%). Reference concrete
   mix was also made for comparative reasons.
           Results proved that adding of waste plastic fibres with these percentages leads to
   improvements in compressive strength and Splitting Tensile Strength of concretes containing
   plastic fibres, but the improvement in Splitting Tensile Strength appeared more clearly.
            There is significant improvement in low-velocity impact resistance of all waste
   plastic fibres reinforced concrete (WPFRC) mixes over reference mix. Results illustrated that
   waste plastic fibres reinforced mix of (1.5%) give the higher impact resistance than others,
   the increase of its impact resistance at failure over reference mix was (328.6%) while, for
   waste plastic fibres reinforced mix of (0.5%) was (128.6%) and it was (200%) for fiber
   reinforced mix of (1%).
           Some photos were taken to the microstructures of concrete by using Scanning
   Electronic Microscope (SEM) and Optical Microscope.

   Keywords: Fiber Reinforced Concrete, Waste Plastic Fiber, Impact, Mechanical Properties,
   Gap-graded Concrete.

 1. INTRODUCTION

           Since ancient times, fibers have been used to reinforce brittle materials. Straw was
   used to reinforce sun-baked bricks, and horsehair was used to reinforce masonry mortar and
   plaster. A pueblo house built around 1540, believed to be the oldest house in the U.S., is

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 constructed of sun-baked adobe reinforced with straw. In more recent times, large scale
 commercial use of asbestos fibers in a cement paste matrix began with the invention of
 the Hatschek process in 1898. Asbestos cement construction products are widely used
 throughout the world today. However, primarily due to health hazards associated with
 asbestos fibers, alternate fiber types were introduced throughout the 1960s and 1970s (1).

2. FIBER REINFORCED CONCRETE

         Concrete is considered a brittle material as it has low tensile strength and failure
 strain. It is difficult to suppress the formation and growth of cracks developed therein and
 is apt to be fractured by tensile load or dynamic load. To resolve these drawbacks and to
 prolong the service duration of concrete, fiber-reinforced concrete has been developed in
 which fibers are incorporated to improve the mechanical properties (2).
 Fiber-reinforced concrete, or fiber concrete, is a composite. It takes the advantages of the
 high compressive strength of concrete and the high tensile strength of fibers. Furthermore,
 it increases the energy absorption capacity of concrete through the adhesion peeling off,
 pulling out, bridging, and load transmitting of fibers in the concrete, and improves the
 ductility, toughness, and impact strength(2).
         The strength potential of nylon-fiber-reinforced concrete was investigated versus
 that of the polypropylene-fiber-reinforced concrete by Song et al(3). The compressive and
 splitting tensile strengths and modulus of rupture (MOR) of the nylon fiber concrete
 improved by 6.3%, 6.7%, and 4.3%, respectively, over those of the polypropylene fiber
 concrete. On the impact resistance, the first-crack and failure strengths and the percentage
 increase in the post first-crack blows improved more for the nylon fiber concrete than for
 its polypropylene counterpart.
         Poly(vinyl butyral) (PVB) which has many special engineering aggregate
 properties is utilized as the sole aggregate in a research done by Xu et al(4) to develop a
 novel cementitious composite reinforced with Poly (vinyl alcohol) (PVA) fiber . Impact
 energy absorption capacity is evaluated based on the Charpy impact test. The results show
 that PVB composite material has lower density but higher impact energy absorption
 capability compared with conventional lightweight concrete and regular concrete. The
 addition of PVA fiber improves the impact resistance with fiber volume fractions. A
 model based on fiber bridging mechanics and the rule of mixtures is developed to
 characterize the impact energy. A good correlation was obtained for the materials tested
 when experimental results are compared to those predicted by the developed model.
         Experimental investigations were conducted by Song et al(5) on tyre fiber
 specimens with different variables such as length, diameter of holes and percentage of
 coarse aggregate replacement by tyre fibers. Impact resistance test was done by ACI
 standard and acid and water absorptions tests were conducted by Indian standard. Results
 obtained from the tests are use to determine the optimum size of the tyre fiber specimen
 that could be used in the rubberized concrete mixture to give the optimum performance.
 The rubberized concrete with tyre fiber specimen L50-D5 10% has shown good transport
 characteristics and impact resistance.




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3. WASTE PLASTIC FIBER REINFORCED CONCRETE

         Alhozaimy(6) study the effects of using recycled fibers (RP) from industrial or post
 consumer recycled plastic waste as reinforcing fibers in concrete. The mechanical properties,
 plastic shrinkage cracking and permeability of RP fibrous concrete were investigated. Four
 different volume fractions (1, 2, 3 and 4%) of recycled plastic low density polyethylene fibers
 (RP fibers) and control with no RP fibers were considered.
 The results showed that at volume fraction of 1 to 2% of RP fibers, plastic shrinkage cracking
 was almost similar to plain concrete without RP fibers (i.e., 0%) while at a volume fraction of
 3 to 4 %, no plastic shrinkage cracks were observed. Also, it was found that RP fibers have
 no significant effect on the compressive and flexural strengths of plain concrete at volume
 fractions used in this study. However, the RP fibers increased flexural toughness up to 270%.
         Yadav(7) investigates the change in mechanical properties of concrete with the
 addition of plastics in concrete. Along with the mechanical properties, thermal characteristics
 of the resultant concrete is also studied .This research found that the use of plastic aggregates
 results in the formation of lightweight concrete. The compressive, as well as tensile strength
 of concrete reduces with the introduction of plastics. The most important change brought
 about by the use of plastics is that the thermal conductivity of concrete is reduced by using
 plastics in concrete.
         Thirty kilograms of waste plastic of fabriform shapes was used by Ismail (8) et al as a
 partial replacement for sand by 0%, 10%, 15%, and 20% with 800 kg of concrete mixtures.
 All of the concrete mixtures were tested at room temperature. These tests include performing
 slump, fresh density, dry density, compressive strength, flexural strength, and toughness
 indices. Seventy cubes were molded for compressive strength and dry density tests, and 54
 prisms were cast for flexural strength and toughness indices tests. Curing ages of 3, 7, 14, and
 28 days for the concrete mixtures were applied in this work. The results proved the arrest of
 the propagation of micro cracks by introducing waste plastic of fabriform shapes to concrete
 mixtures. This study insures that reusing waste plastic as a sand-substitution aggregate in
 concrete gives a good approach to reduce the cost of materials and solve some of the solid
 waste problems posed by plastics.

3. EXPERIMENTAL PROGRAM

3.1. Materials
 3.1.1. Cement
          Ordinary Portland Cement (OPC) ASTM Type I is used. The cement is complied to
  Iraqi specification no.5/ 1999(9)

3.1.2. Fine Aggregate
                Natural gap-graded sand is used in production of concrete specimens which was
  used in this study. Results of sieve analysis of this sand are shown in Table (1).

3.1.3. Coarse Aggregate
              Gap-graded uncrushed course aggregate is used for all concrete mixes in this
  study. Table (2) gives the sieve analysis results of that course aggregate.




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                                         Table (1): Sieve Analysis Results of the Sand Used.

                                                                                  Percent Passing
  No                     Sieve Size (mm)                                              Limits of British Standard
                                                            Fine aggregate
                                                                                Specifications (BSS. 882 (Zone 1))(10)
   1                             4.75mm                          100                            90-100
   2                             2.36mm                          46.6                            60-95
   3                             1.18mm                          4.6                             30-70
   4                            600micron                        0.28                            15-34
   5                            300micron                         0                              5-20
   6                            150micron                         0                              0-10


                                120                                                             Lower Passing
                                                                                                Percentage
                                100            100
                                                       95                                       Upper Passing
         Percentage Passing %




                                               90
                                 80                                                             Percentage
                                                                 70                             Actual Fine Agg.
                                 60                    60                                       Grading
                                                       46.6
                                 40
                                                                         34
                                                                 30
                                 20                                              20
                                                                         15
                                                                                         10
                                                                 4.6             5
                                  0                                      0.28    0       0



                                                            Seive Size (mm)
                                             Fig.1: Grading of fine aggregate used in this study.



                                        Table (2): Sieve Analysis Results of the Gravel Used.

                                                                                  Percent Passing
  No          Sieve Size (mm)                                                   Limits of British Standard Specifications
                                                      Coarse aggregate
                                                                                        (BSS. 882 (Zone 1))(10)
   1                                  37.5                      100                               95-100
   2                                   20                        80                                30-70
   3                                  10.0                      18.8                               10-35
   4                                   5.0                      1.2                                 0-5




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                                   120

                                   100         100
                                               95
            Percentage Passing %


                                    80                   80
                                                         70                              Lower Passing
                                    60                                                   Percentage
                                                                                         Upper Passing
                                    40                                                   Percentage
                                                                        35
                                                         30                              Actual Coarse
                                    20                                  18.8             Aggregate Grading
                                                                        10
                                                                                 5
                                    0                                            1.2
                                                                                 0
                                          37.5mm     20mm       10mm           5mm
                                                      Seive Size (mm)



                                         Fig.2: Grading of coarse aggregate used in this study.


3.1.4 Mixing Water
             Ordinary tap water is used in this work for all concrete mixes and curing of
  specimens.

3.1.5. Plastic Fiber
          Plastic fibers with average 1cm length and average 2mm width were produced by
  cutting plastic beverage bottles by hand.

3.2. Preparation of Specimens and Curing.
         The moulds were lightly coated with mineral oil before use, according to ASTM
  C192-88(11), concrete casting was carried out in three layers. Each layer was compacted by
  using a vibrating table until no air bubbles emerged from the surface of concrete and the
  concrete is levelled off smoothly to the top of moulds.

3.3 Mixing and Compaction of Concrete
          Mixing operations were made in the concrete laboratory in the civil engineering
  department of University of. A 0.1m3 pan mixer was used. Pouring the coarse aggregates
  made mixing and cement in two alternate times and mixing them dry while adding the fibers
  until a homogenous dry mix is obtained. The water is added then and mixing continued until
  final mixing mix is obtained.
  The concrete mix is poured, in three layers, in the molds. An electrical vibrator made
  compaction for not more than 10 sec.




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3.4. Mixes
  Table (3): Mix Proportions of Materials Used in this Work for Making One Cubic Meter of
                                                  Concrete.
                                                                    Waste Plastic Fibers
                  Cement       Sand       Gravel      Water
      Symbol                                                        Waste         Waste
                   (kg)        (kg)        (kg)       Liter
                                                                   Plastic        Plastic
                                                                  Fibers(kg)     Fibers%
       RC          412.5       618.7       1237        185.6          0              0
       F0.5        410.4       615.6      1231.2       184.7         5.5           0.5%
       F1.0        408.4       612.6      1225.12      183.8          11            1%
       F1.5        406.3        609       1218.94      182.8         16.5          1.5%

3.5. Tests
3.5.1. Compressive Strength Test
          The compressive strength of concrete is one of the fundamental properties used to
  specify the quality of concrete. The digital hydraulic testing machine (ELE) with capacity of
  (2000) KN and rate of 3 KN/Sec, is used for the determination of compressive strength of
  concrete. Three cubes of (100×100×100) mm concrete were tested according to B.S.1881.
  Part(5):1989(12). The average of three cubs was recorded for each testing age (7, 28 and 56)
  days respectively for compressive strength.
3.5.2. Spletting Tensile Strength
          Splitting tensile strength was conducted on cylinders of (100mm diameter and 200mm
  height according to ASTM C496-05 (13). The average of three specimens in each case was
  taken. The splitting tensile strength was determined by using the digital hydraulic testing
  machine (ELE) with capacity of (2000) KN and rate of (0.94) KN/Sec. The average of three
  cylinders was recorded for each testing age (7, 28 and 56) days respectively for splitting
  tensile strength.
3.5.3. Low Velocity Impact Test
           Eight 56-day age (500 × 500 × 50) mm slab specimens were tested under low
  velocity impact load. The impact was conducted using 1400gm steel ball dropping freely
  from height equal to 2.4m. The test rig used for low velocity impact test consists of three
  main components: Plate (1).
          A steel frame, strong and heavy enough to hold rigidly during impact loading. The
  dimensions of the testing frame were designed to allow observing the specimens (square slab)
  from the bottom surface to show developing failure, during testing. The specimen was placed
  accurately on mold which were welded to the support ensure the simply supported boundary
  condition.
          The vertical guide for the falling mass used to ensure mid-span impact. This was a
  tube of a round section.
          -Steel ball with a mass of 1400 gm.
          -Specimens were placed in their position in the testing frame with the finished face
  up. The falling mass was then dropped repeatedly and the number of blows required to cause
  first crack was recorded. The number of blows required for failure (no rebound) was also
  recorded.

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                    Plate (1): Test Rig Used for Low Velocity Impact Test

4-RESULTS AND DISCUSSION

4.1. Compressive Strength
           Figs. (3) and (4) show the variation the compressive strength with waste plastic fiber
  percentages for all ages. From these figures it can be seen that, the compressive strength of all
                                    ut
  specimens increases with time, but the percentage of increasing in compressive strength differs
  between the reference concrete RC and the fiber reinforced concrete FRC. Table (4) show the
  results of compressive strength of all mixes in this research.
                                              values
           All the mixes have shown strength values above (35) MPa at 56 day age. Fiber reinforced
  mixes with waste plastic fibers percentage by volume (Vf%) equal to (0.5%) and (1%) have a
  compressive strength more than that of reference mix at 56 age of test. The maximum value of
                           o
  increment was equal to (7.5%) for concrete mix containing (1%) waste plastic fiber. The
  compressive strength of mix with (Vf=1.5%) decrease if comparing with reference mix at 28 day
                                                                                         segregate
  and 56 day ages. The reason of this is the fiber after which (1%) had formed bulks and segregat
  on mix. This led to form stiff bond about these bulks.

                 Table (4): Compressive Strength of FRCs at Different Ages with
                                         Compressive strength (MPa) at indicated ages in
                 Waste plastic fibers                           (day)
      Mix
                        Vf %
                                                7                 28             56
      RC                  0                   26.4                33            41.2
     FR0.5               0.5                  23.4                32            41.3
     FR1.0                1                   27.3                34            44.3
     FR1.5               1.5                   26                 29             35



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                                                         45


                                                          43
                                                                             Vf% of waste plastic fibers

                                                                                           0%
                                                         40
                                                                                           Vf=0.5%
                                                                                           Vf=1%




                            Compressive Strength (MPa)
                                                          38
                                                                                           Vf=1.5%


                                                         35


                                                          33


                                                         30


                                                          28


                                                         25


                                                          23


                                                         20
                                                                   8        13        18        23        28        33        38        43        48        53        58
                                                               5       10        15        20        25        30        35        40        45        50        55        60
                                                                                                           Age (Day)
           Fig. 3: The relationship between compressive strength and age for all mixes.




                                                                                                                                                                           Compressive Strength (Mpa)
                                                                                                               41.2                                              60
                                                                             44.3               41.3
                                                               35                                                             33
                                                                                           34              32                                                40
                                                                       29                                                               26.4
                                                                                                   27.3             23.4                                                                                0%
                                                                                 26                                                                          20                                         0.5%

                                                                                                                                                            0                                           1%
                                                                                                                                                                                                        1.5%
                                                                                                                                             0%
                                                                                                                     0.5%
                                                                                                     1%
                      Age (Day)                                              1.5%

                                                                                 Vf% of waste plastic fibers




        Fig.4: Development of Compressive Strengths for all Concrete Mixes at All Ages.

4.2. Splitting Tensile Strength
          The results of splitting tensile strength for various types of concrete specimens at age
  (7, 14, 56) days. The relationship between splitting tensile strength and various ratios of
  waste plastic fiber is shown in figures (5) and (6). It can be seen that the addition of waste
  plastic fibers leads to increase of remarkable splitting tensile strength but it decreases after
  (Vf=1% ) of waste plastic fiber ,but it is still higher than the splitting of reference concrete. The
  increase is due to the fact that the presence of waste plastic fibers arrests cracks progression.
  Also we can note that the plain concrete cylinders fail suddenly and split into two separate
  parts, while the mode of failure in cylinders with waste plastic fibers is cracked at failure
  without separation. The maximum splitting tensile strength is obtained at mixing containing
  (1%) waste plastic fiber by volume.


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              Table (5): Splitting Tensile Strength of FRCs at Different Ages
                                      Compressive strength (MPa) at indicated ages in
              Waste plastic fibers                           (day)
    Mix
                     Vf %
                                               7                28             56
    RC                 0                     0.88                1            1.44
   FR0.5              0.5                   0.884              1.04           1.6
   FR1.0               1                    1.138              1.57           1.7
   FR1.5              1.5                      1               1.38           1.38


                                                       1.80
                                                                             Vf% of waste plastic fibers

                                                        1.70                           0%
                                                                                       Vf=0.5%

                                                       1.60                            Vf=1%
                                                                                       Vf=1.5%
                    Splitting Tensile Strength (MPa)




                                                        1.50


                                                       1.40


                                                        1.30


                                                       1.20


                                                        1.10


                                                       1.00


                                                        0.90


                                                       0.80
                                                                    8        13        18        23        28        33        38        43        48        53                                  58
                                                               5         0
                                                                        10        15        20        25        30        35        40        45        50               55                           60
                                                                                                            Age (Day)
       Fig.5: The relationship between splitting tensile strength and age for all mixes.
                                                                                                                                                              Splitting Tensile Strength (Mpa)




                                                                                            1.7 1.6                                                2
                                                                                                    1.44
                                                                                               1.57
                                                                             1.38
                                                                                                                                                   1.5
                                                                                  1.13                   1.04 1
                                                                                                      1.132
                                                                                             1              0.884 0.88                             1                                                       0%
                                                                                                                                                                                                           0.5%
                                                                                                                                                   0.5
                                                                                                                                                                                                           1%
                                                               56                                                                                  0
                                                                                                                                                                                                           1.5%
                                                                         7                                                          0%
                                                                                                           1%        0.5%
                                                                                            1.5%
                   Age (Day)
                                                                                       Vf% of waste plastic fibers



   Fig.6: Development of Seplitting Tensile Strengths for all Concrete Mixes at All Ages.


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4.3. Impact Resistance and Mode of Failure
          The impact resistance of concrete slabs was determined in terms of the number of
  blows required to cause complete failure of the slabs. The mass of (1400 gm) was repeatedly
  dropped for a (2400 mm) height up to the failure of slabs. Two sets of number of blows were
  recorded depending on the mode of failure: at first crack and at failure. Total fracture energy
  here is the product of the height of the drop (2.4 m) and weight of the dropped mass (1.4 kg)
  by the number of blows to failure. The results of low velocity impact tests of all mixes at
  age of (56) days are presented in Table (4) below, it can be seen that there is a significant
  improvement in the low-velocity impact resistance for the all mixes containing waste plastic
  over reference mix. Fig.(7) shows the effect of adding waste plastic which were added as a
  percentage by volume of the concrete at first crack and failure. It can be seen that, when the
  ratio of waste plastic: concrete percentage increased the impact resistance also increased. For
  a (1.5%) ratio the number of blows reached to (30) blows at failure while they recorded as
  (16) at first crack (each result average for two specimens). The increase of its impact
  resistance at failure over reference mix was (328.6%). Fig.(8) showed the relationship
  between impact resistance and splitting tensile strength at failure.
          From figures (7), (8) and (9) it can be noticed that, at percentage of (1.5%) of waste
  fiber add to concrete, the specimens show a good resistance to fracture due to the distribution
  of fiber across the concrete. That means the increase in tension stress, ductility, more energy
  absorption and bond strength.
          Some photos were be taken to the microstructure of WPFRC by optical microscope in
  the laboratories of Iraqi Ministry of Sciences and Technology and other photos were be taken
  by Scanning Electronic Microscope Technology (SEM) in the labs of South West Jiaotong
  University-China. Plate (2) and Plate (3) show the waste plastic fiber inside the
  microstructure of concrete.

                         Table (4): Results of impact test at 56 days age

                         No. of blows to first         No. of blows to
                                                                            Total energy (Nm)
                                crack                      failure
   Panels      Vf %
                                                                            First
                          Results      Mean        Results       Mean                  Failure
                                                                            crack
     RC                      6                          8
                  0                      5                         7        164.8      230.72
                             4                          6
   FR0.5                     9                         17
                 0.5                     9                        16        296.64     527.36
                             9                         15
                             14                        18
   FR1.0          1                      13                       21        428.48     692.16
                             12                        24
                             15                        33
   FR1.5         1.5                     16                       30        527.36      988.8
                             17                        27




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                                                                                              30




                                                                                               25                  Impact Resistance

                                                                                                                          First Crack




                                                           Impact Resistance (No. of Blows)
                                                                                                                          Final Failure

                                                                                              20




                                                                                               15




                                                                                              10




                                                                                                   5




                                                                                               0
                                                                                                                   0.3                          0.8               1.3
                                                                                                       0.0                       0.5                       1.0          1.5
                                                                                                                            (Vf%) of Wast Plastic Fibers


 Fig. 7: The relationship between impact resistance (number of blows) and fiber content by
                                     volume for all mixes.




                                                1.8
                                                                                                             Polynomial



                                                 1.7
              Splitting Tensile Strngth (MPa)




                                                1.6



                                                 1.5



                                                1.4



                                                 1.3



                                                1.2
                                                                                               8                          13                          18          23          28
                                                       5                                                      10                          15                 20         25         30
                                                                                                   Impact Resistance (No. of Blows Until Failure)

 Fig. 8: The relationship between splitting tensile strength and impact resistance (number of
                                    blows) and for all mixes.




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                                         988.8
                                                                                    1000




                                                                                           Total Energy (Nm)
                                                    692.16                          800

                                                             527.36
                                                                                    600
                                           527.36
                                                       428.48
                                                                        230.72      400
                                                                   296.64
                                                                            164.8
                                                                                    200

                            Failure                                                 0
                           First crack
                                                                             0%
                                                        1%         0.5%
                                           1.5%              Vf%




 Fig. 9: The relationship between total energy and waste plastic fiber content by volume for
                                            all mixes.




                        a                                     b
                    50X
         Plate(2):a-50X photo of WPFRC microstructure by optical microscope.
               200X
            b-200X photo of WPFRC microstructure by optical microscope.




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                                                                                    b
                                a




                                c

                     Plate(3):a-150X photo of WPFRC microstructure by SEM.
                         b-150X photo of WPFRC microstructure by SEM.
                         c-200X photo of WPFRC microstructure by SEM.


5. CONCLUSION
         Based on the expiremental work and results obtained in this study, the following conclusions can
 be presented:

 1. Addition of waste plastic fibers with different volume ratios to gap-graded concrete slightly increases
 the compressive strength up to (Vf=1%) at ages 7, 28, and 56 days comparing with the original mix. The
 maximum values of increasing were about (3%) for 28 days and (7.5%) for 56 days age for WPFRC mix
 with (Vf=1%) .
 2. Addition of waste fiber with different volume ratios to gap-graded concrete increases the splitting tensile
 strength for WPFRC mixes at ages 28, and 56 days comparing with the original mix. The max. value of
 increasing is (57%) for 28 day while (18%) for 56 days age for the mix with (Vf=1%) of waste plastic fiber
 to . Another mixes also show increasing in the splitting tensile strength but not as (1%) percentage.
 3. A significent improvement in the low velocity impact resistance of all gap-graded mixes modified with
 waste plastic fibers over reference mix. The increase in the waste plastic fibers percentage gives higher
 number of blows at both first crack and failure comparing with reference mix. The amount of increasing
 varied from (128.5% ) at (Vf= 0.5%) to (328.6%) for (1.5%) volume ratio at failure.
 4. Results of this study open the way to use of waste plastic for developing the performance properties of
 gap-graded concrete and extension in studying the hole properties of gap-graded concrete containing these
 kind of fibers.

                                                     130
 International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME

 ACKNOWLEDGMENT

             I would like to express my extreme and very special thanks and appreciation to
 Dr. Fuhi Li - Department of Civil Engineering Material - School of Civil
 Engineering/Southwest Jiaotong University for his assistance in preparing samples and taking
 SEM for these samples.

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