Thesis Open Access

Stabilization& Microstructure modification of dispersive soil using sugarcane bagasse Ash (Case study on Gidole-wozeka Road)

Abeneazer Alemayehu

Thesis supervisor(s)

Eleyas Assefa (PhD)

Dispersive subgrade soils are one of the known causes of road failure. Replacement of
dispersive soils with natural construction materials is an expensive and sometimes not economically viable solution. On the other hand, commonly used chemical stabilizations of
dispersive soils are either costly or not environmentally friendly. Sugarcane Bagasse Ash
(SCBA) is cheap compared to other chemical stabilizers, and it is a pozzolana material rich
in silica and aluminium and sometimes in calcium oxides. Besides, using industrial wastes
for soil stability reduces the environmental risks induced by industrial wastes. Ethiopia
has the potential to produce 1.9 million tonnes annually. This work investigates the use of
SCBA as a stabilizer for dispersive soils. Grain size distribution, Atterberg limit, compaction, CBR, and UCS tests were conducted according to AASHTO standard for natural and
treated subgrade soil. The disturbed soil samples were collected from five locations with
1.5m depth and 200m intervals. Later, we conducted SAR and PS chemical tests to determine the dispersive potential of the soil. 0%, 5%, 10%, 15%, and 20% amount of SCBA
by dry mass and 7 days, 14 days, and 21 days of curing periods were applied to examine the
index and strength property of soil. The microstructural arrangements of the soils before
and after treatment were analysed using SEM test. The results show SCBA and curing
period have impacts on index properties of dispersive subgrade soils. The treated subgrade
soils had high MDD and low OMC compared to the natural subgrade soils that mean that
SCBA stabilization with curing periods could improve the strength of dispersive subgrade
soils. The results also show the CBR values increased above 15% and improved the soil’s
consistency to stiff with increasing the SCBA amounts up to 20% and the curing period
to 21 days, which indicates the treated subgrade soils were very good. SCBA could also
reduce the dispersion potential and alter the microstructure of dispersive soils. It forms
numerous well-defined patterns on the soil surface that minimizes the dispersed nature of
the subgrade soils.

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