HIGHWAY LABORATORY

CIVIL ENGINEERING DEPARTMENT

SULTAN AZLAN SHAH POLYTECHNIC

EXPERIMENT : 3

TITLE : MARSHALL STABILITY TEST

3.1 INTRODUCTION

The test is applicable to hot mix designs using bitumen and aggregates up

to a maximum size of 25mm. In this method, the resistance to plastic deformation

of cylindrical specimen of bituminous mixture is measured when the same is

loaded at periphery at 5 cm per min. This test procedure is used in designing and

evaluating bituminous paving mixes. The test procedure is extensively used in

routine test programmer for paving jobs. There are two major features of the

Marshall method of designing mix namely,

i) Density - voids analysis

ii) Stability - flow tests.

The Marshall stability of mix is defined as a maximum load carried by a

compacted specimen at a standard test temperature of 60ºC. The flow value is

deformation the Marshall test specimen under goes during the loading up to the

maximum load, 0.25 mm units. In this test and attempt is made to determine

optimum binder content for the type of aggregate mix and traffic intensity..

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3.2 OBJECTIVE

This method covers the measurement of resistance to plastic flow of

cylindrical specimens of asphalt mixtures loaded on the lateral surface by means

of the Marshall apparatus. This method is for use with mixtures containing

asphalt cement, asphalt cutback, and aggregate up to 25.4 mm maximum size

The testing section of this method can also be used to obtain maximum load and

flow for asphalt concrete specimens cored from pavements or prepared by STP

204-8, Preparation of Marshall Compaction Specimens.

3.4 APPARATUS

Clockwise from top :

Marshall tester, water bath and

Breaking head

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Figure on the left shows the mold for the

speciment

3.5 PROCEDURES

1. Thoroughly clean the guide rods and the inside surfaces of the test heads prior to

making the test, and lubricate the guide rods so that the upper test head slides

freely over them.

2. Bring the specimens prepared with asphalt cement to the specified temperature

by immersing in a water bath 30 minutes. Maintain the bath or oven temperature

at 60 ± 1oC for asphalt cement specimens.

3. Bring the specimens prepared with asphalt cutback to the specified temperature

by placing them in the air bath for a minimum of 2 hours. Maintain the air bath

temperature at 25 ± 1o C. The testing head temperature shall be maintained

between 20 to 38o C.

4. Remove the specimen from the water bath, oven or air bath and place in the

lower segment at the breaking head.

5. Place the upper segment of the breaking head on the specimen and place the

complete assembly in position on the testing machine.

6. Place the flow meter, where used, in position over one of the guide rods and

adjust the flow meter to zero while holding the sleeve firmly against the upper

segment of the breaking head.

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7. Hold the flow meter sleeve firmly against the upper segment of the breaking head

while the test load is being applied.

8. Apply the load to the specimen by means of the constant rate of movement of the

load jack or testing machine head of 50.8 mm/minute until the maximum load is

reached and the load decreases as indicated by the dial.

9. Record the maximum load noted on the testing machine or converted from the

maximum micrometer dial reading.

10.Release the flow meter sleeve or note the micrometer dial reading, where used,

the instant the maximum load begins to decrease. Note and record the indicated

flow value or equivalent units in mm if a micrometer dial is used to measure the

flow. The elapsed time for the test from removal of the test specimen from the

water bath to the maximum load determinations shall not exceed 30 seconds.

3.6 DATA COLLECTION

Results obtained can be presented in the charts that follows

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3.8 DISCUSSION

This paper presents the results of a study attempting to determine the relationship

between the particle size-gradation and the optimum binder content (OBC) in a Marshall

asphalt-concrete mix. The analysis was based on Marshall results of more than 250

mixes, all of which conform to the Ministry of Public Works’ specifications. Multivariate

linear regression analysis was used to calibrate the model shown in Equation 2.

The analysis of results showed a high correlation between the OBC and the particle size

distribution. The cumulative percent passing values were used to describe the particle

size distribution. A separate model was calibrated for each of the asphalt-concrete

mixes: Type I, Type II, Type III, Type IV and PMS. A combined (aggregated) model

was developed for mix types I, II, III and IV due to the similarity of sieve sizes used to

describe their aggregate-blends’ size gradations.

Additional data were used to validate the aggregated model for mix types I, II, III, and

IV. This resulted in a correlation between the predicted and observed OBC with an R2

of 0.73.

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3.9 CONCLUSION

The developed models can be used to estimate the required OBC for a given aggregate

blend. Using this calculated OBC, three identical specimens of a Marshall mix may be

prepared, tested, and checked for compliance to specifications for air voids, stability,

density, flow, and VMA. This results in major time and effort savings of laboratory work.

Additional results of other mixes are needed to further validate the use of the developed

models. This can be accomplished by calculating OBC values using the models of

Table 3, and comparing the results with the actual OBC values obtained by conducting

a conventional Marshall test.

Similar analysis can be performed on any asphalt-concrete mix design results (such as

those of Superpave mixes); but this remains to be determined. However, high

correlations are always expected because of the high dependency of OBC on the

particle size distribution of the used aggregate blend, which is described by the

cumulative percent passing of the sieve analysis results.

3.10 REFERENCES

Various sources from the internet

www.wikipedia.com

http://training.ce.washington.edu

http://www.surface-engineering.net

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http://theconstructor.org/

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