AIM
To determine the Marshall stability of bituminous mixture as per
ASTM D 1559.
PRINCIPLE
Marshall stability is the resistance to plastic flow of cylindrical
specimens of a bituminous mixture loaded on the lateral surface.
It is the load carrying capacity of the mix at 60 °C and is
measured in kg.
APPARATUS
MARSHALL STABILITY APPARATUS
i) Marshall stability apparatus
ii) Balance and water bath
SAMPLE
From Marshall stability graph, select proportions of coarse
aggregates, fine aggregates and filler in such a way, so as to fulfill
the required specification. The total weight of the mix should be
1200g.
PROCEDURE
i) Heat the weighed aggregates and the bitumen separately
upto 170 °C and 163 °C respectively.
ii) Mix them thoroughly, transfer the mixed material to the
compaction mould arranged on the compaction pedestal.
iii) Give 75 blows on the top side of the specimen mix with a
standard hammer (45cm, 4.86kg). Reverse the specimen
and give 75 blows again. Take the mould with the specimen
and cool it for a few minutes.
iv) Remove the specimen from the mould by gentle pushing.
Mark the specimen and cure it at room temperature,
overnight.
v) A series of specimens are prepared by a similar method
with varying quantities of bitumen content, with an increment
of 0.5% (3 specimens) or 1 bitumen content.
vi) Before testing of the mould, keep the mould in the water
bath having a temperature of 60 °C for half an hour.
vii) Check the stability of the mould on the Marshall stability
apparatus.
REPORTING OF RESULTS
Plot % of bitumen content on the X-axis and stability in kg on
the Y-axis to get maximum Marshall stability of the bitumen mix.
A sample plot is given in Annexure-X
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