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

PREPARATION OF SAMPLE FOR MODIFIED BITUMINOUS MIXES

The samples are prepared by adding polyethylene and kerosene with pure bitumen. The amounts of polyethylene and kerosene are added by weight of percentage of pure bitumen separately.

First of all fresh bitumen, without debris and adulterants was collected. The properties of the bitumen were justified. Five bowls for preparing samples was weighed. Hot bitumen was poured in those bowls. The weight of the bitumen was taken. Then polyethylene was weighed with respect to 1%, 2%, 3%, 4%, and 5% weight of the bitumen. The kerosene was also weighed with respect to 1%, 2%, 3%, 4%, and 5% weight of the bitumen. The samples were prepared one after another. At first the bitumen for 1% polyethylene and 1% kerosene content was heated till it fully liquefied and was in a state to dissolve polyethylene and kerosene. The polyethylene bags were gradually left in the bitumen. The softened form of the polyethylene bags was floating on the hot bitumen. But after continuous stirring by steel spoon it was thoroughly mixed with the bitumen. Though the final mixing temperature was not observed but it is assumed that it was near the flash point of the bitumen. There was a little change in the color. This mother sample is kept for further experiments. Thus five samples were prepared with variable polyethylene and kerosene contents. When a test was to be performed the sample was thoroughly heated so that a homogeneous liquid state could be gained and neither precipitation nor floatation nor suspension was observed.

Sample-1. Weight of pure bitumen + 1% polyethylene of pure bitumen + 1% kerosene of pure bitumen (by weight)

Sample-2. Weight of pure bitumen + 2% polyethylene of pure bitumen + 2% kerosene of pure bitumen (by weight)

Sample-3. Weight of pure bitumen + 3% polyethylene of pure bitumen + 3% kerosene of pure bitumen (by weight)

Sample-4. Weight of pure bitumen + 4% polyethylene of pure bitumen + 4% kerosene of pure bitumen (by weight)

Sample-5. Weight of pure bitumen + 5% polyethylene of pure bitumen + 5% kerosene of pure bitumen (by weight).