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Concrete Laboratory-Experiment 3- Compaction Factor Test-Yee Pin

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					                         BACHELOR OF CIVIL ENGINEERING JUNE 2011


Experiment 3- Compacting Factor Test

1.0 Introduction

       The compacting factor test is a more sensitive method of measuring the workability of
concrete than the slump test, and enables values to be obtained for mixes which are too dry to
give a measurable slump. In this test the density of the concrete after a standardized degree of
partial compaction is compared with the density of the concrete after full compaction.


       It consists of two conical hoppers and a cylindrical container mounted vertically above
one another. In the test, the top hopper is filled with a sample of concrete which is not
compacted. A hinged door at the bottom is released and the concrete is similarly released
from the lower hopper and falls into the cylindrical container. The use of two hoppers helps to
reduce any inconsistencies caused by uneven loading of the top hopper. Cohesive mixes have
a tendency to stick in one or both of the hoppers; if this happens, the concrete may be helped
through by pushing a rod gently into the concrete from the top. The concrete above the level
of the rim of the cylindrical container is cut off by simultaneously working two steel floats
from the outside to the centre.


       The weight of concrete in the cylinder is found and is referred to as the partially
compacted weight. The corresponding weight of fully compacted concrete is then found by
refilling the cylinder in layers approximately 50mm deep, each layer being compacted by
hand-ramming or vibration, and toweling off the concrete level with the rim. The concrete in
the cylinder s again weighed, and the compacting factor is the ratio of the partially compacted
weight to the fully compacted weight; a higher value indicates greater workability. To ensure
a representative result for the workability of a particularly important batch, such as a trial mix,
it is advisable to take the average of the values obtained from three tests.




Experiment 1 - Concrete Mix Design                                                         Page 1
                       BACHELOR OF CIVIL ENGINEERING JUNE 2011


2.0 Objectives of Experiment


    To determine the workability for a given volume of wet concrete sample which
      determines its ability to be placed, compacted and finished as required for the specific
      purpose using the Compaction Factor Test Method.




3.0 Apparatus of Experiment


   1. Balance (accurate to 0.01 g)
   2. Wet Concrete Sample
   3. Two Metal Floats, Scoop, Trowel
   4. Compaction Factor Apparatus
   5. 25mm Square Tamping Rod




Experiment 1 - Concrete Mix Design                                                     Page 2
                         BACHELOR OF CIVIL ENGINEERING JUNE 2011


4.0 Procedures


1. The empty cylinder is weighted using the scales or balance which is capable of weighing
  up to 25kg and accurate to within 10g and the mass to the nearest 10g is recorded.
2. The internal surfaces of the hoppers and cylinder is ensured to be smooth, clean and damp
  but free from superfluous moisture. The frame is placed in a position free from vibration or
  shock in such a manner that it is stable with the axes of hoppers and the cylinder all lying
  on the same vertical line. The two trap doors are closed and two floats are placed on the
  cylinder so as to cover its top.
3. The sample of concrete is gently placed in the upper hopper using the scoop until the
  hopper is filled to the level of the rim. The upper trap door is opened so that the concrete
  falls into the lower hopper. Immediately after the concrete has come to rest, the floats are
  removed from the top of the cylinder and the trap door of the lower hopper is opened to
  allow the concrete to fall into the cylinder.
4. Certain mixed have a tendency to stick in one or both of the hoppers. If this occurs, help
  the concrete through by pushing the tamping rod gently into the concrete from the top until
  the lower end emerges from the bottom of the hopper. If this does not dislodge the
  concrete, the rod is raised and the process is repeated until the concrete falls through the
  hopper. The number of times the concrete rodded is counted as this provides a guide to the
  cohesiveness of the concrete.
5. The excess concrete remaining above the level of the top of the cylinder is cuter off by
  holding a float in each hand, with the plane of the blades horizontal, and moving them
  simultaneously one from each side across the top of the cylinder. The outside of the
  cylinder is wiped clean.
6. Within 150s of placing the sample in the upper hopper, the cylinder and its contents is
  weighted, the mass of the partially-compacted concrete to the nearest 10g is calculated and
  recorded.
7. The partially-compacted concrete is emptied from the cylinder and refilled it with concrete
  from same sample in such a way as to remove as much entrapped air as possible (without
  significantly reducing the amount entrained air, if present) and to produce full compaction
  of the concrete with neither excessive segregation nor laitance. For this purpose by means
  of the scoop, the concrete is placed in the six cylinders in six layers approximately equal in
  depth and compact each layer by using either the compacting bar or the vibrator. After the


Experiment 1 - Concrete Mix Design                                                      Page 3
                          BACHELOR OF CIVIL ENGINEERING JUNE 2011


  top layer has been compacted, it level is smoothed with the top of the cylinder, using one
  of the plasterer’s floats, and the outside of the cylinder is wiped clean. The cylinder and its
  contents are weighted to the nearest10 g, and the mass of the empty cylinder are
  subtracting, the mass of the fully-compacted concrete to the nearest 10g is calculated and
  recorded.



5.0 Calculation and Formulas


                               The Compaction Factor = W2 – W1
                                                        W3 – W1


Where:
W1              = Weight of Cylinder (kg)
W2 – W1         = Weight of Partially Compacting Concrete Sample (kg)
W3 – W1         = Weight of Fully Compacting Concrete Sample (kg)




6.0 Results


From the Compaction Factor Test Method:
     Weight of Cylinder (kg)                                                   -
                                                                    (cause no measurement)
     Weight of Partially Compacting Sample(kg)                               13.82
     Weight of Fully Compacting Concrete Sample(kg)                          14.55
     Compacting Factor Ratio                                                 0.95


Compacting Factor = Mass of Partially Compacted Concrete
                       Mass of Fully Compacted Concrete
                     = 13.82
                       14.55
                     = 0.95



Experiment 1 - Concrete Mix Design                                                       Page 4
                        BACHELOR OF CIVIL ENGINEERING JUNE 2011


7.0 Discussion
       The Compaction Factor Test Method for the workability of wet concrete sample must
within 45 minutes after the mixing. The category for workability was different from the slump
test category where in the slump test the specimen was categories as high workability. The
discrepancy for the workability between both tests was due to evaporation of water between
both tests since compacting factor was done after the slump test. The other reason for this
discrepancy was the loss of water due to surface contact between hopper, sampling tray and
specimen.



8.0 Recommendation
 Before pour the concrete into the hoppers, make sure all the trap doors are closed.
 The excess of concrete should be removed before the cylinder is weighted to get the
    exactly value of uncompacted value.


9.0 Conclusion
       It can be seen from the results that the compacting factor test, we get ratio of the two
masses was 0.95. That was a medium workability of wet concrete which are only suitable for
the application in the normal purpose reinforced concrete because the ratio between the range
of 0.85 -0.95.


       It was still not suitable for the high quality structural concrete, mass concrete which
the range of ratio between 0.75-0.85. The quantities of water in the mix designs of concrete
should be reduce where it’s will help to achieve a better workability and higher quality. The
more workable concrete, the higher will be the compacting factor. This type of workability is
suitable to be used for normal purpose and reinforced concrete.




10.0 Bibliography
    B.S.:1881; 1983; Part 101- Method of Sampling
    BS 1881: 1983; Part 103- Compacting Factor Test
    http://www.engineeringcivil.com/
    http://www.ca-oman.com/res/


Experiment 1 - Concrete Mix Design                                                      Page 5
                        BACHELOR OF CIVIL ENGINEERING JUNE 2011


11.0 Appendices




Picture 1: Picture show the sample of concrete are gently poured into the compaction factor
apparatus.




  Pictures 2: Picture show that the upper trap door is opened so that the concrete falls into
  the lower hopper.



Experiment 1 - Concrete Mix Design                                                    Page 6
                         BACHELOR OF CIVIL ENGINEERING JUNE 2011




  Picture 3: Picture show that the trap door of the lower hopper is opened and to allow the
  concrete to fall into the cylinder.




   Picture 4: Picture shows that the concrete and the cylinder are weighted and recorded.




Experiment 1 - Concrete Mix Design                                                   Page 7

				
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