Stabilization of residual soil with alkali-activated fly ash and inclusion of treated coir fibre
Residual soils have not been always conducive to construction road and other structures. Alkaline activation (AA) is one of the beneficial soil improvement techniques used to improve the geotechnical characteristics of soils with a new generation of cementitious binders. However, soil stabilized...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/77660/1/FK%202019%2040%20ir.pdf |
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| Summary: | Residual soils have not been always conducive to construction road and other structures.
Alkaline activation (AA) is one of the beneficial soil improvement techniques used to
improve the geotechnical characteristics of soils with a new generation of cementitious
binders. However, soil stabilized with alkali-activated binders will cause to post-peak
brittleness. Therefore, coir fibres were incorporated in the stabilized soil as a source of
discrete reinforcement to improve the mechanical properties of the soil. The mechanical
performance of the reinforced soils depends on the nature of the soil and fibre as well the
interaction between the fibre and the alkaline activation stabilized soil.
The present work focuses on investigating the use of a locally available by-product (fly
ash) as precursor in alkaline activation reactions as well as treated coir fibres as discrete
reinforcement. Surface treatment was applied through an agent including linseed oil and
turpentine oil in order to improve its durability in alkaline environment as well as tensile
strength and to minimize the biodegradable nature of fibre in soil. Moreover, to confirm
the alteration of morphology in the fibres and understand the underlying mechanisms of
treated fibres, field emission scanning electron microscopy (FESEM) and energydispersive
X-ray spectroscopy (EDX) tests were performed. Furthermore, the
mechanical properties of soil matrix were assessed. A series of laboratory tests including
compaction, unconfined compressive strength tests (UCS), indirect tensile strength tests
(ITS), flexural strength tests (FS), direct shear tests (DS) and California bearing ratio
tests (CBR) were carried out on original soil, alkali activated stabilized soil, alkali
activated stabilized soil reinforced with untreated and treated fibres. The contents were
varied from 40% to 70% of dried soil by weight for fly ash and 1% of dried soil by weight
for treated coir fibres. The specimens were cured in for 7 and 28 days.
The results revealed that the linseed oil treated fibres increased the tensile strength up to
183% compared with untreated fibres. The fibres treated with linseed oil showed higher
mechanical performance compared with the fibres treated by turpentine oil. The FESEM/EDX results showed that cellulosic pores of the fibres contain Al and Si which
form network like bonds, tightly wrapped around the fibres. The compressive strength,
indirect tensile strength and flexural strength of the treated soil increased by 37, 7 and
93%, respectively, when linseed oil treated fibres were used compared with those of
alkali activated stabilized soil with untreated fibres. Moreover, the addition of linseed
oil-treated fibres increased the shear strength parameters and California bearing ratio of
soil. According to the microstructural analysis, the interaction between the fibre surface
and the geo-polymeric matrix is the main factor contributing to enhanced behaviour of
the reinforced mixtures. This research is important that it confirms that the surface
treatment can-not only increase the mechanical performance of coir fibres but also
improves the interfacial mechanical interactions between the fibre surface and soil
particles, resulting in a higher performance of the composites used as the road subgrade. |
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