Marshall Stability Test as per ASTM D 1559 & IRC 111
OBJECTIVES
To determine the strength (Marshall Stability Value) and flexibility (flow value) for the given bitumen mixture.
To determine the density-voids analysis for the given bituminous mixture;
To determine the suitability of bituminous mixture to meet the specified criteria for the surface course.
INTRODUCTION
Bruce Marshall, formerly bituminous engineer with Mississippi State Highway Department, USA formulated Marshall Method for designing bituminous mixes.
This test is done to determine the Marshall stability of bituminous mixture. The principle of this test is that Marshall Stability is the resistance to plastic flow of cylindrical specimens of a bituminous mixture loaded on the lateral surface at 5 cm per minute. It is the load carrying capacity of the mix at 60 degree and is measured in kg.
The sample needed is 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 1200 gm for one specimen.
CONCEPT AND SIGNIFICANCE
The test procedure is used in designing and evaluating bituminous paving mixes and is widely applied in routine test programmes for the paving jobs. The major features of the Marshall Method of designing mixes are to determine the two important properties of strength and flexibility.
Strength is measured in terms of the “Marshall’s Stability” of the mix which is defined as the maximum load carried by a compacted specimen at a standard test temperature of 60 degree. This temperature represents the weakest condition for a bituminous pavement in use.
The flexibility is measured in terms of the “Flow Value” which is measured by the change in diameter of the sample in the direction of lad application between the start of loading and the time of maximum load. In this test an attempt is made to obtain optimum binder content for the aggregate mix type and traffic intensity.
EQUIPMENT/APPARATUS
The apparatus for the Marshall Stability test consists of the following:
Specimen Mould Assembly comprising mould cylinders 10 cm diameter x 7.5 cm height, base plate and extension collars. They are designed to be interchanged with either end of cylindrical mould. Three mould cylinders are recommended.
Specimen extractor for extracting the compacted specimen from the mould. A suitable bar is required to transfer load from the extension collar to the upper proving ring attachment while extracting the specimen
Compaction Rammers having a flat circular tamping face 4.5kg sliding weight constructed to provide a free fall of 45.7cm. Two compaction rammers are recommended.
Compaction pedestal consisting of a 20 x 20 x 45 cm wooden block capped with a 30
30 x 2.5 cm MS plate to hold the mould assembly in position during compaction. Mould holder is provided consisting of spring tension device designed to hold compaction mould in place on the compaction pedestal.
Breaking head. The Breaking head consist of upper and lower cylindrical segments or test heads having an inside radius curvature of 5 cm. The lower segment is mounted on a base having two perpendicular guide rods which facilitate insertion in the holes of upper test segments. assembly with provision to fix flow meter
Loading Machine motorized, loading machine is provided with a gear system to lift the upward direction. Recalibrated proving ring of 5 tone capacity is fixed on the upper end of the machine, specimen contained in the test head is placed in between the base and the proving ring. The loading jack produces uniform vertical movement of 5 cm/ min. Machine is capable of reversing its movement downward also. This facilitates adequate space for placing test head system. After one specimen has been tested.
Flow Meter. The flow meter consists of guide sieve and a gauge. The activating pin of the gauge slides inside the guide sleeve with a slide amount f fractional resistance. Least count of 0.025mm is adequate. The flow value refer top the total vertical upward movement form the initial position at zero load to value at maximum load. The dial; gauge at the flow meter should be able to measure accurately the total vertical movement upward.
In addition to the above the following general equipments are also required
Oven or hot plates Mixing Apparatus
Water Bath
Thermometer of range up to 2000C with sensitively of 2.5 degree Celsius
Miscellaneous Equipment's are like container, mixing and handling tools etc.
PREPARATION OF TEST SPECIMEN
The coarse aggregates, fine aggregates, and the filler materials should be proportioned so as to fulfill the requirements of the relevant standards. The required quantity of the mix is taken so as to produce compacted bituminous mix specimens of thickness 63.5 mm approximately.
Take 1200 gm of coarse aggregates, fine aggregates and filler material (as per grading requirement given in table) to produce the desired thickness.
The aggregates are heated to a temperature of 175° to 190°C the compaction mould assembly and rammer are cleaned and kept pre-heated to a temperature of 100°C to 145°C.
The bitumen is heated to a temperature of 121°C to 138°C and the required amount of first trial of bitumen is added to the heated aggregate and thoroughly mixed using a mechanical mixer or by hand mixing with trowel.
The mixing temperature for 110 grade bitumen may be around 154°C and that for 60/70 grade about 160°C.
The total quantity of mix is placed in a mould and compacted by rammer with 75 blows. Invert the sample, and compact the other face with the same number of blows.
The compacting temperature should be about 138°C for 80/100 grade bitumen and 149°C for 60/70 grade.
After compaction, invert the mould. With the collar of the bottom, remove the base and extract the sample by pushing it out the extractor.
The compacted specimen should have a thickness of 63.5 mm.
Allow the sample to stand for a few hours to cool.
Obtain the sample’s mass in air and submerged, to measure density of specimen, so as to allow, calculation of the voids properties.
NOTES:
At least 2 specimens (but preferably 3 or 4 specimen) for each combination of aggregate and bitumen should be prepared.
For surface course with 12 mm aggregate, the expected optimum bitumen content may be about 6.5 %. Therefore specimen should be made at 5.5 %, 6.0 %, 6.5 %, 7.0 % and 7.5 % bitumen content.
TEST PROCEDURE
In conducting the stability test, the specimen are heated at a temperature of 60 ±10 C (37.8 ± 10C for specimens in which tar has been used in place bitumen), either in a water bath for 30-40 minutes or in an oven for a minimum of 2 hours.
Remove the specimens from the water bath (or oven) and place the lower segment of the breaking head. Then place the upper segment of the breaking head on the specimen and place the complete assembly in position of the Marshall testing machine.
Place the flow meter (dial gauge) over one of the post and adjust into read zero.
Apply a load at a rate of 50 mm per minute until the maximum load reading is obtained.
Record the maximum load in Newton (N). At the same instant obtain the flow as recorded on the flow meter in unit of mm.
The total time between removing the specimen from the bath and completion of the test should not exceed 30 seconds.
RECORD OF OBSERVATIONS
Mass of aggregates in mixing pan = 1200 gm
Mass of bitumen added ………………………………… gm
Bitumen content …………………………………………… %
Heating Temperature Aggregates ………………… 0C Bitumen ……………………. 0C
Mixing ……………………….0C
Compacting temperature ………………………………0C
Number of blows with hammer per face ………Nos
Mass of specimen in air ‘Wm” ………………………. gm
Mass submerged ‘Ww’ ……………………………….. gm
Diameter of Specimen …………………………………. cm
Thickness of specimen …………………………………. cm
Volume of specimen ‘Vm’ ……………………………….. cm3
NOTE:
The measured stability of a specimen multiplied by the ration for the thickness of specimen is equal to the corrected stability for a 63.5 mm specimen.
Volume-thickness relationship is based on a specimen diameter of 10 cm.
Detailed procedure along with calculations, correction factors etc is attached below.
OBJECTIVES
To determine the strength (Marshall Stability Value) and flexibility (flow value) for the given bitumen mixture.
To determine the density-voids analysis for the given bituminous mixture;
To determine the suitability of bituminous mixture to meet the specified criteria for the surface course.
INTRODUCTION
Bruce Marshall, formerly bituminous engineer with Mississippi State Highway Department, USA formulated Marshall Method for designing bituminous mixes.
This test is done to determine the Marshall stability of bituminous mixture. The principle of this test is that Marshall Stability is the resistance to plastic flow of cylindrical specimens of a bituminous mixture loaded on the lateral surface at 5 cm per minute. It is the load carrying capacity of the mix at 60 degree and is measured in kg.
The sample needed is 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 1200 gm for one specimen.
CONCEPT AND SIGNIFICANCE
The test procedure is used in designing and evaluating bituminous paving mixes and is widely applied in routine test programmes for the paving jobs. The major features of the Marshall Method of designing mixes are to determine the two important properties of strength and flexibility.
Strength is measured in terms of the “Marshall’s Stability” of the mix which is defined as the maximum load carried by a compacted specimen at a standard test temperature of 60 degree. This temperature represents the weakest condition for a bituminous pavement in use.
The flexibility is measured in terms of the “Flow Value” which is measured by the change in diameter of the sample in the direction of lad application between the start of loading and the time of maximum load. In this test an attempt is made to obtain optimum binder content for the aggregate mix type and traffic intensity.
EQUIPMENT/APPARATUS
The apparatus for the Marshall Stability test consists of the following:
Specimen Mould Assembly comprising mould cylinders 10 cm diameter x 7.5 cm height, base plate and extension collars. They are designed to be interchanged with either end of cylindrical mould. Three mould cylinders are recommended.
Specimen extractor for extracting the compacted specimen from the mould. A suitable bar is required to transfer load from the extension collar to the upper proving ring attachment while extracting the specimen
Compaction Rammers having a flat circular tamping face 4.5kg sliding weight constructed to provide a free fall of 45.7cm. Two compaction rammers are recommended.
Compaction pedestal consisting of a 20 x 20 x 45 cm wooden block capped with a 30
30 x 2.5 cm MS plate to hold the mould assembly in position during compaction. Mould holder is provided consisting of spring tension device designed to hold compaction mould in place on the compaction pedestal.
Breaking head. The Breaking head consist of upper and lower cylindrical segments or test heads having an inside radius curvature of 5 cm. The lower segment is mounted on a base having two perpendicular guide rods which facilitate insertion in the holes of upper test segments. assembly with provision to fix flow meter
Loading Machine motorized, loading machine is provided with a gear system to lift the upward direction. Recalibrated proving ring of 5 tone capacity is fixed on the upper end of the machine, specimen contained in the test head is placed in between the base and the proving ring. The loading jack produces uniform vertical movement of 5 cm/ min. Machine is capable of reversing its movement downward also. This facilitates adequate space for placing test head system. After one specimen has been tested.
Flow Meter. The flow meter consists of guide sieve and a gauge. The activating pin of the gauge slides inside the guide sleeve with a slide amount f fractional resistance. Least count of 0.025mm is adequate. The flow value refer top the total vertical upward movement form the initial position at zero load to value at maximum load. The dial; gauge at the flow meter should be able to measure accurately the total vertical movement upward.
In addition to the above the following general equipments are also required
Oven or hot plates Mixing Apparatus
Water Bath
Thermometer of range up to 2000C with sensitively of 2.5 degree Celsius
Miscellaneous Equipment's are like container, mixing and handling tools etc.
PREPARATION OF TEST SPECIMEN
The coarse aggregates, fine aggregates, and the filler materials should be proportioned so as to fulfill the requirements of the relevant standards. The required quantity of the mix is taken so as to produce compacted bituminous mix specimens of thickness 63.5 mm approximately.
Take 1200 gm of coarse aggregates, fine aggregates and filler material (as per grading requirement given in table) to produce the desired thickness.
The aggregates are heated to a temperature of 175° to 190°C the compaction mould assembly and rammer are cleaned and kept pre-heated to a temperature of 100°C to 145°C.
The bitumen is heated to a temperature of 121°C to 138°C and the required amount of first trial of bitumen is added to the heated aggregate and thoroughly mixed using a mechanical mixer or by hand mixing with trowel.
The mixing temperature for 110 grade bitumen may be around 154°C and that for 60/70 grade about 160°C.
The total quantity of mix is placed in a mould and compacted by rammer with 75 blows. Invert the sample, and compact the other face with the same number of blows.
The compacting temperature should be about 138°C for 80/100 grade bitumen and 149°C for 60/70 grade.
After compaction, invert the mould. With the collar of the bottom, remove the base and extract the sample by pushing it out the extractor.
The compacted specimen should have a thickness of 63.5 mm.
Allow the sample to stand for a few hours to cool.
Obtain the sample’s mass in air and submerged, to measure density of specimen, so as to allow, calculation of the voids properties.
NOTES:
At least 2 specimens (but preferably 3 or 4 specimen) for each combination of aggregate and bitumen should be prepared.
For surface course with 12 mm aggregate, the expected optimum bitumen content may be about 6.5 %. Therefore specimen should be made at 5.5 %, 6.0 %, 6.5 %, 7.0 % and 7.5 % bitumen content.
TEST PROCEDURE
In conducting the stability test, the specimen are heated at a temperature of 60 ±10 C (37.8 ± 10C for specimens in which tar has been used in place bitumen), either in a water bath for 30-40 minutes or in an oven for a minimum of 2 hours.
Remove the specimens from the water bath (or oven) and place the lower segment of the breaking head. Then place the upper segment of the breaking head on the specimen and place the complete assembly in position of the Marshall testing machine.
Place the flow meter (dial gauge) over one of the post and adjust into read zero.
Apply a load at a rate of 50 mm per minute until the maximum load reading is obtained.
Record the maximum load in Newton (N). At the same instant obtain the flow as recorded on the flow meter in unit of mm.
The total time between removing the specimen from the bath and completion of the test should not exceed 30 seconds.
RECORD OF OBSERVATIONS
Mass of aggregates in mixing pan = 1200 gm
Mass of bitumen added ………………………………… gm
Bitumen content …………………………………………… %
Heating Temperature Aggregates ………………… 0C Bitumen ……………………. 0C
Mixing ……………………….0C
Compacting temperature ………………………………0C
Number of blows with hammer per face ………Nos
Mass of specimen in air ‘Wm” ………………………. gm
Mass submerged ‘Ww’ ……………………………….. gm
Diameter of Specimen …………………………………. cm
Thickness of specimen …………………………………. cm
Volume of specimen ‘Vm’ ……………………………….. cm3
NOTE:
The measured stability of a specimen multiplied by the ration for the thickness of specimen is equal to the corrected stability for a 63.5 mm specimen.
Volume-thickness relationship is based on a specimen diameter of 10 cm.
Detailed procedure along with calculations, correction factors etc is attached below.
