Marshel stability test and its procedure

Procedure 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 60oC and is measured in kg.

:

pic:- MARSHALL STABILITY APPARATUSAPPARATUS:-
i) Marshall stability apparatus
ii) weigh 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 (12.5mm,10mm, 4.75mm, 2.6mm).

PROCEDURE:
i) Heat the weighed aggregates and the bitumen separately upto 170 degree C and 163 degree 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 60oC for half an hour.
vii) Check the stability of the mould on the Marshall stability apparatus.


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.

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