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Tuesday, November 15, 2011

EXPERIMENT marshall stability and flow test for bitumen


Introduction

The Marshall stability and flow test provides the performance prediction measure for the Marshall mix design method. The stability portion of the test measures the maximum load supported by the test specimen at a loading rate of 50.8 mm/minute. Load is applied to the specimen till failure, and the maximum load is designated as stability. During the loading, an attached dial gauge measures the specimen's plastic flow (deformation) due to the loading. The flow value is recorded in 0.25 mm (0.01 inch) increments at the same time when the maximum load is recorded. The important steps are as follows;
Step 1; sample is weigh as following table;
Table 1.0; Mix ratio
Material
%
gm
20 mm aggregate
38
427.56
10mm aggregate
8
90.00
Q. Dust
52
585.00
Cement
2
22.50
Total
100 %
1125.00

g 1.0; Aggregate samples
Step 2; The sample is kept in oven to dry, till the sample reaches 150 deg C.

Fig 1.1; Dry oven
Step 3; to make the temperature rise faster, the sample was placed in fry pan and mixed well, and frequently check the temperature of the sample if it has reached 150 deg C.
Step 4; Bitumen sample is weight as following (table 2) and the aggregate and cement from the table 1 in the fry pan are been mixed .
Table 2; bitumen weight
1
4.5 %
53.00 gm
2
5.0 %
59.20 gm
3
5.5 %
65.50 gm
4
`6.0 %
71.80 gm
5
6.5 %
78.20 gm

Fig 1.2; Bitumen and aggregate sample been mixed in fry pan
Step 5; the 1st sample is poured in to the mould after mixing it in the fry pan, and the sample is left for its temperature inside the mould has reached 130 deg C.
Step 6; When the temperature has reached 130 deg C, the sample is placed in the Marshal compactor, Marshal Compactor gives an impact load x75 times and this is done on the both sides (top and bottom).

Fig 1.3; Marshall Compactor
Step 7; Compaction process is completed, the sample is removed from the mould, and label the sample, so that it won’t be confuse with other samples.
The above steps are repeated for all the samples, after that measure the thickness of each sample, if any sample is less than 60mm consider it as failure, recode all the reading in lab table (Marshall Test results). Measure the weight of each sample in Air, Water and saturated. Before Marshall test, the sample must be place in water bath for 45 min to 1 hour at a temperature of 160 deg C.

Fig 1.4; Marshal property curve
Table 3
Marshall properties
% Bitumen contant optim curve
Critenia
Space limit
Stability
5.0
1.384
> 750 Kg
Flow
5.2
3.6
>2.0 mm
Density
5.5
2.365
-
UFB
5.2
8.0
75 % - 85 %
VIM
5.0
4.0
3% - 5%
Optimum B/contant
5.18
-
-

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