PREPARATION OF TEST SPECIMEN FOR MARSHALL METHOD

The coarse aggregates, fine aggregates and the filter materials should be proportioned and mixed specified gradation of mineral aggregates and bitumen binder as per IRG: 29–1968 are given in Table. The aggregates and filler are mix together in the desired proportion as per the design requirements and fulfilling the specified gradation. The required quantity of the mix is taken so as to produce a compacted bituminous mix specimen of thickness 63.5mm, approximately.

Approximately 1200g of aggregates and filler are taken and heated to a temperature of 175⁰ to 190⁰C. The compaction mould assembly and rammer are cleaned and kept pre-heated to a temperature of 100⁰C to 145⁰C. The bitumen is heated to temperature of 121⁰C to 138⁰C and the required quantity of first trial percentage of bitumen (say, 3.5% by weight of mineral aggregates) is added to the heated aggregate and thoroughly mixed using a mechanical mixer or by hand mixing with trowel. The mixing temperature for 80/100grade bitumen may be around 154⁰C and that for 60/70grade, about 160⁰C.The mix is placed in a mould and compacted by rammer, with 50 blows on either side. The compacting temperatures may be about 138⁰C for 80/100grade bitumen and 149⁰C for 60/70grade. The compacted specimen should have thickness of 63.5mm. The weight of the aggregate taken may be may be suitably altered to obtain a thickness of 63.5±3.0 mm.  At least two specimens, but preferably three or four specimens should be prepared at each trial bitumen content which may be varied at 0.5 percent increments up to about 7.5 or 8.0 percent.

 

Specified Grading of Aggregates for Bituminous Concrete

Passing Sieve size	Retained Sieve size	Weight of Aggregate (gm)
20 mm	12.5 mm	120
12.5 mm	9.5 mm	120
9.5 mm	4.75 mm	240
4.75 mm	2.36 mm	216
2.36 mm	600 micron	216
600 micron	300 micron	72
300 micron	150 micron	72
150 micron	75 micron	84
75 micron	Filler	60
Total =		1200 gm

CHARACTER OF MATERIALS ARE USED IN MODIFIED BITUMINOUS MIXES

Characteristics of Materials used in modified bitumen:

i)          Bitumen

ii)         Polyethylene

i)                    Kerosene

ii)                   Ice

iii)                 Greece

iv)                 Stone aggregate

v)                  Fine aggregate

vi)        Filler materials.

 

Pure Bitumen

i)        Penetration grade: 80/100

ii)       Specific gravity: 1.02

iii)     Ductility value: 100⁺

iv)     Flash point: 290 ⁰C

v)      Fire point: 300 ⁰C

vi)     Softening point: 43 ⁰C

vii)  Solubility: 95.7%

 

Polyethylene

A particular type of polythene bags, transparent in color, mostly representing the low-density polyethylene purchased from the local market is used. Specific gravity of this specimen varies from 0.95 to 0.93.
 

Coarse Aggregate

It was collected from the hump beside Strength of Materials Lab, Transportation Lab, and from site of under construction Computer Science and Engineering building. The white stone aggregate was used with rather mix of black stone. The aggregate was to pass through 20 mm sieve. Other sieves where retained aggregates were collected are   12.5mm, 9.5mm, 4.75mm and 2.36mm.

Fine Aggregate

Fine aggregate of grade 2.36mm passing and retained at 600mm, 300mm, 150mm, and 75 mm. It was collected from the construction site of new student hostel.

Mineral Filler

It was the residuals received after sieving the fine aggregate in the soil lab by mechanical shaker. It was passed through 75mm sieve.