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Concrete Laboratory-Experiment 4-Concrete Cube Density Test- Yee Pin

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Concrete Laboratory-Experiment 4-Concrete Cube Density Test- Yee Pin Powered By Docstoc
					                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


Experiment 4 - Concrete Cube Density Test


1.0 Introduction / Theory


        The density test is a very important tool used to control the quality of freshly mixed
concrete. After a concrete mix proportion has been established, a change in the concrete’s
density will indicate a change in one or more of the other concrete performance requirements.
A lower density may indicate:
            That the materials have changed.
            Higher air content.
            Higher water content.
            A change in the proportions of ingredients.
            Lower cement content.
Conversely, the higher density would indicate the reverse of the above-mentioned concrete
characteristics.




2.0 Objectives of Experiment
     To determine the density of the concrete sample test cubes such that the properties of
        both the fresh and hardened material are as required for the specific purpose using the
        Concrete Cube Density Test Method.
     To determine the compressive strengths of mix hardened concrete based on measured
        the density of concrete.




Experiment 4 - Concrete Cube Density Test                                                Page 1
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


3.0 Apparatus of Experiment


     2 cube mould (size mould: 150mm x 150mm x 150mm)
     Vibration machine (optional: tamping rod)
     Scoop
     Trowel
     Water tank
     Paint brush
     Brush and Oil mould
     2 samples of cured concrete
     Spanners
     Calipers
     Container with Clean Water
     Ruler
     Marker Pen
     Balance (accurate to 0.01 g)




Experiment 4 - Concrete Cube Density Test                            Page 2
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


4.0 Procedures
    1. The inner contact surfaces of the cube mould are coated with some mould oil before
        placing and the base plate in order to ensure that no water escapes.
    2. The intension surface of the assembled mould is also required to be coated with
        mould oil to prevent adhesion of concrete. Using a scoop, the freshly mixed concrete
        is placed into the mould in three equal lifts, rod each lift 25 times for cube.
    3. The 2 cube of moulds sample is placed on the vibrating table.
    4. The wet concrete sample is taken and placed layer inside the cube mould.
    5. The layer cube mould is vibrated on 1 minute to let the sample gets compacted.
    6. The step 4 is repeated with the second and third layer.
    7. The sample of concrete of the cube mould then will be leveled off and finished it.
    8. The sample is labeled on the upper surface. It is then left for 24 hours.
    9. After the 24 hours, the mould is opened and then it placed inside the water for curing
        purpose.(Strength measurement at 28 days)
    10. The specimens are taken out of the tank and/or moist curing room at the 24 hours of
        testing.
    11. The De-molded specimen is placed aside to clean the exterior of the measure
        thoroughly so that all excess concrete is removed.
    12. The reading for the length, width and height of specimens measured and recorded for
        four times repeated according to the British Standard requirement.
    13. The weight of concrete is weighed and recorded.




Experiment 4 - Concrete Cube Density Test                                                 Page 3
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


5.0 Calculation and Formulas


                                 Volume, v         = L x W x H (m3)
Where;
     V = Volume (mm³)
     L = Length (mm)
     W = Width (mm)
     H = Height (mm)


                               Density, P        = m1/v       (kg/m3)


Where;
     ρ = Density of Concrete Sample Test Cube (kg/m³)
     M = Weight of Concrete Sample Test Cube (kg)
     V = Volume of Concrete Sample Test Cube (mm³)




Experiment 4 - Concrete Cube Density Test                               Page 4
                                 BACHELOR OF CIVIL ENGINEERING JUNE 2011


      6.0 Results
         Sample No       Sample Marking               Length                    Width         Height
                                                        (mm)                    (mm)           (mm)
                                                        146.70                  148.00        146.64
                                                        147.34                  149.70        146.70
              1                   B1
                                                        146.00                  141.30        146.60
                                                        146.34                  141.62        146.76
                                                        143.70                  154.30        145.00
                                                        142.10                  152.00        145.04
              2                   B2
                                                        144.72                  151.50        144.66
                                                        142.64                  152.50        145.00
                                                        151.61                  150.78        148.08
                                                        151.44                  151.20        149.70
              3                   B3
                                                        152.08                  150.63        149.29
                                                        151.58                  151.03        150.86
                                                        149.42                  151.59        151.59
                                                        148.35                  152.14        151.58
              4                   B4
                                                        153.14                  151.93        151.73
                                                        152.03                  152.78        151.72




Sample    Sample       Average Average Average                   Volume,          Weight,   Density,    Percentage
 No      Marking       Length,       Width,       Height,           v               m1,        P                of
                           L            W           H          LxWxH                         m1/v          Error
                                                                    3                              3
                         (mm)          (mm)       (mm)            (m )              (kg)    (kg/m )         (%)
  1          B1         146.60       145.16       146.68     3.121 x 10-3          7.930    2540.85         8.14
  2          B2         143.29       152.58       144.93     3.168 x 10-3          7.860    2481.06         6.53
  3          B3         151.68       150.91       149.48     3.422 x 10-3          7.890    2305.67         1.37
                                                                           -3
  4          B4         150.74       152.11       151.66     3.477 x 10            7.790    2240.44         2.93




      Experiment 4 - Concrete Cube Density Test                                                        Page 5
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


7.0 Data and Sample Calculation


For Sample Marking ‘A’
Average Length, L = L1 + L2 + L3 + L4
                                  4
                      = 146.70 + 147.34+ 146.00 + 146.34
                                            4
                      = 146.60 mm


Average Width, W = W1 + W2 + W3 + W4
                                  4
                      = 148.00 + 149.70+ 141.30 + 141.62
                                            4
                      = 145.16 mm


Average Height, H = H1 + H2 + H3 + H4
                                  4
                      = 146.64 + 146.70+ 146.60 + 146.76
                                            4
                      = 146.68 mm


Volume, v             = Lavg x Wavg x Havg
                      = 146.60 mm x 145.16 mm x 146.68 mm
                      = 3.121 x 106 mm3
                      = 3.121 x 10-3 m3


Density, P            =Weight
                        Volume
                      = 7.930 kg
                     3.121 x 10-3 m3
                      = 2540.85 kg/m3




Experiment 4 - Concrete Cube Density Test                            Page 6
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


Theoretically,
Dimension of specimens of cube = 150mm (L) x 150mm (W) x 150mm (H)
                                      = 3.375 x 106 mm3
                                      = 3.375 x 10-3 m3


Density of cube A, P                  = Weight
                                            Volume
                                      = 7.930 kg
                                      3.375 x 10-3 m3
                                      = 2349.63 kg/m3


For Cube A
Percentage of Error (%)               = Measured result- Accepted value    x 100 %
                                                     Accepted value
                                      = 2540.85 – 2349.63         x 100%
                                                2349.63
                                      = 8.14 %




Experiment 4 - Concrete Cube Density Test                                            Page 7
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


8.0 Discussion


        The result obtained from the experiment contains error by comparing it to theory.
There is a small variation between actual and theoretical data. The error occurred are due to
several factors. The factors are:-


    A. Human Error
         Improper use of cube mould because cube mould was not tighten properly.


    B. Apparatus Failure
         Due to un-even surface of the cube mould because of pro-long usage so it caused
           the cube mould might be slightly deformed.
         The apparatus should be calibrated after a certain period.




9.0 Recommendation


 While finishing off the surface of the concrete, if the mould is too full, the excess concrete
   should not be removed by scraping off the top surface as this takes off the cement paste
   that has come to the top and leaves the concrete short of cement. The correct way is to use
   a corner of the trowel and dig out a fair sample of the concrete as a whole, and then finish
   the surface by toweling.
 Once a specimen has been compacted, it should not be left standing on the same bench as
   another specimen that is being compacted. If this is done, some vibration will be passed on
   to the first specimen and it will be more compacted than the other. In extreme cases some
   re-arranging of the particles may result and segregation will occur.
 Do not hit the on specimens when de-mould, hit the boundary of the mould lightly using a
   hammer to remove the mould from specimens. Hardly hit on the specimens can lead the
   concrete damage followed by decreasing the strength of specimens.




Experiment 4 - Concrete Cube Density Test                                                 Page 8
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


10.0 Conclusion


        The measured result obtain from the mixed concrete is different from theoretical
result where the density of percentage difference between the theory and experiment for
specimens B1, B2, B3 and B4 are about 8%.


        The different result are due to the dimension of specimens must measured several
times for the experiment by using an equipment such as vernier caliper to obtain the actual
value of volume of specimens, mean while the volume of specimens theoretically is assume
as 150mm x 150mm x 150mm. Therefore, error can be avoided by using the idea suggested
above in order to obtain more accurate result. The value of density gained from the can use to
determine the strength of the specimens on further test which is concrete cube compressive
strength test.




11.0 Bibliography

         B.S.:1881; 1983; Part 101- Method of Sampling
         BS 1881:1983; Part 107; -Density of Compacted Fresh Concrete
         BS 1881:1983; Part 108; - Making Test Cube from Fresh Concrete
         BS 1881:1983; Part 110; - Density of Hardened Concrete
         B.S.:1881; 1983; Part 112- Curing
         http://findarticles.com/
         http://www.cityu.edu.hk/CIVCAL/home.html




Experiment 4 - Concrete Cube Density Test                                               Page 9
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011


12.0 Appendices




             Picture 1: Picture show the Concrete sample being put into the cubes.




  Picture 2: Picture shows that the freshly mixed concrete is placed into the mould in three
                             equal lifts, rod each lift 25 times for cube.




Experiment 4 - Concrete Cube Density Test                                              Page 10
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011




  Picture 3: Picture shows that the cube is being full by the concrete on the vibrating table
                                            machine.




  Picture 4: Picture shows that the specimens are placed for curing until the day of testing.




Experiment 4 - Concrete Cube Density Test                                               Page 11
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011




          Picture 5: Picture shows that the exterior of the excess concrete is cleaned.




  Picture 6: Picture shows that the specimens of cube are measured using vernier calipers.




Experiment 4 - Concrete Cube Density Test                                                 Page 12
                           BACHELOR OF CIVIL ENGINEERING JUNE 2011




   Picture 7: Picture shows that the inner surface of cube being clean using the oil mould.




  Picture 8: Picture shows that the inner contact surfaces of the cube mould are coated with
  some mould oil before placing and the base plate in order to ensure that no water escapes.



Experiment 4 - Concrete Cube Density Test                                              Page 13

				
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