Marshall stability measures the maximum load sustained by the bituminous material at a loading rate of 50.8 mm/minute. The test load is increased until it reaches a maximum. Beyond that, when the load just starts to decrease, the loading is ended and the maximum load (i.e. Marshall stability) is recorded. During the loading test, dial gauge is attached which measures the specimen’s plastic flow owing to the applied load. The flow value refers to the vertical deformation when the maximum load is reached.
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Marshall stability is related to the resistance of bituminous materials to distortion, displacement, rutting and shearing stresses. The stability is derived mainly from internal friction and cohesion. Cohesion is the binding force of binder material while internal friction is the interlocking and frictional resistance of aggregates. As bituminous pavement is subjected to severe traffic loads from time to time, it is necessary to adopt bituminous material with good stability and flow.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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am having problem in reading the flow value in marshal stabiliyty test and necessary calculation in reporting
if stability test fail, what should we do.
1st of all you have to find out the root causes and cross check the combined grading and individual hot bin gradings. Also check the finer content of Dust. It is necessary to check the bitumen content from the batch mix report of plant. If everything seems to be okay, then you have to re-design it.