Test-7

 

ASPHALT CONTENT BY CENTRIFUGAL EXTRACTION

 

 

Objective:

 

i)                    To separate the asphalt aggregate mixture.

ii)                   To determine the asphalt content in the mixture.

 

Theory:

 

The asphalt content in the asphalt aggregate mixture is the major constituent to form the good binding between aggregate. The amount of asphalt content in the mixture is essential to know while constructing highway pavement. It also helps to verify the specification.

 

The asphalt content in the mixture are extracted by centrifuge extraction. For this process centrifuge extractor are used. The chemical Trichloroethylene are used. The mixture is rotated by centrifugal force.

 

APPARATUS:

 

i)                    Centrifuge extractor with bowl.

ii)                   Weighing balance

iii)                 Hand tools

-          Spatula, Brush, Pan, Wrench etc.

 

 

MATERIALS:

 

Solvent: Trichloroethylene

 

PROCEDURE:

 

i)                    All equipments and hand tools are cleaned.

ii)                   The sample was taken from the specimen that was prepared for Marshall Stability test.

iii)                 Asphalt mix sample were spread evenly in the bowl.

iv)                 Sample was covered by solvent.

v)                  Bowl was rotated back and forth gently by hand.

vi)                 Filter paper was kept in bowl.

vii)               Tightened the cover plate by wrench.

viii)              The material was allowed to soak for 5 min.

ix)                 Centrifuging was began solvent was collected in the container.

x)                  When flow of extracted liquid stopped to come out then cover plate was opened an aggregate collected in bowl.

xi)                 Again, a little chemical was added with previous effluent.

xii)               Same procedure was continued till all bitumen separated from the mixture.

 

The remaining aggregate was collected, weighted and moisture content was determined.

 

 

 

OBSERVATION AND CALCULATION:

 

Weight of asphalt mix before retraction = 590gm

Weight of dry aggregate after extraction = 533gm

Moisture content = 0

Uncorrected asphalt content = Wt. of asphalt mix – wt. of dry aggregate

                                                             Wt. of dry aggregate

                                              = 590 – 553

                                                      553

                                              = 0.067

Corrected asphalt content = Uncorrected content (%) – Moisture content (%) + extraction error

                                                = 6.7-0-0

                                                = 6.7 %

 

 

 

        CONCLUSION:

 

Hence the asphalt content determined in the lab was found to be 6.7% but when we design premix we                   take 5.5 % bitumen. Some errors are there which may be due to various causes such as spilling of mixture of bitumen and solvent during centrifuging, during weighting of aggregate and bitumen itself.

Though the error was arises which are not so much. Thus result is satisfactory.

 

Hence we are able to determine the asphalt (bitumen) content in bitumen aggregate mixture by centrifuge    extraction.