The Potential Use of Cinder Gravel as A Base Course Material When Stabilized by Volcanic Ash and Lime (The Case of Metehara Area)
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Date
2015-10
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Abstract
This study has been carried out in order to determine the optimum blending proportion of cinder
gravel with volcanic ash and lime. In this regard, an investigation into the improvement of the
natural cinder gravel by stabilization technique was conducted using samples collected from
Metehara area.
In the first phase of investigation, mechanical stabilization was carried out at various proportions
of volcanic ash blended with cinder gravel. Compaction method was used in the determination of
the optimum amount of volcanic ash that makes up the deficiency of fine particles. In this
method, the optimum amount of volcanic ash has been found to be 22% by weight. CBR values
of soaked and unsoaked conditions were determined for cinder gravel stabilized mechanically
with the indicated optimum amount of volcanic ash at 3,7,14 and 28 days of wrapping the sample
in the mold with a polyethylene sheet. The test results showed that the CBR values for all of
these days of wrapping the sample in the mold were more than 80% which is the requirement of
ERA specification for road base while that of the cinder gravel alone was found to be
72%.However, the CBR values were, more or less, not affected by the duration of wrapping the
sample in the mold. In this phase, the CBR value for the soaked condition has been found to be
less than that of the un soaked condition as expected.
In the second phase of investigation, mechanical as well as lime stabilization was carried out
simultaneously in which 20% of volcanic ash and 2% of lime were blended with cinder gravel in
order to find out how the CBR would be changed. Soaked and un soaked conditions at 3,7,14 and
28 days of wrapping and keeping the sample in the mold indicated that the CBR values in this
phase were larger than the corresponding values obtained by blending cinder with volcanic ash
only. The CBR value in this scenario was observed to increase with duration of wrapping and
keeping the sample in the mold unlike the first phase. Furthermore, the CBR value after four
days of soaking was found to be greater than that of the un soaked condition for a given duration
of wrapping the sample in the mold.
Although laboratory investigation in the present study has confirmed that the stabilized cinder
gravel can be used as base course material, field performance of this stabilized material should
be investigated on a pilot project.
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Cinder Gravel, Volcanic Ash, Lime, Metehara