Publication: Performance of marine clay and laterite soil using palm oil fuel ash (pofa) and nano magnesium oxide (mgo) stabilizer with polypropylene reinforcement
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Date
2024-08-01
Authors
Ali Muftah, Abdussalam Ezreig
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Abstract
This research focuses on the use of palm oil fuel-ash (POFA)-activated by
magnesium oxide (MgO) incorporating polypropylene fibres (PPF) for the
stabilisation of tropical soils. Over the past few decades, several challenges have arisen
from the use traditional binders, such as ordinary Portland cement (OPC). The
environmental constraints are primarily driven by the considerable carbon footprint
and the huge amounts of energy consumption when producing such binders. Cement based stabilised soils demonstrate good compressive strength however, it exhibit poor
tensile and flexural strength, displaying brittle behavior. Due to these defects sudden
failure occurs, and this results in low strength, leading to immediate damage to
building structures. Hence, it is imperative to address the aforementioned limitation.
Therefore, magnesium oxide is added to a mixture of palm oil fuel ash and
polypropylene fibers for stabilising and reinforcing marine clay and laterite soil. For
the stabilisation of tropical soil, the four dosages of palm oil fuel ash mixed with
magnesium oxide are 10%, 20% 30%, and 40%. In this research, the adapted
polypropylene fiber proportions are 0.25%,0.50%, 0.75%. The soil specimens
experienced curing, periods of 7, 28, 90 days, during which, a number of tests are
carried out. These tests encompassed evaluations of unconfined compression strength,
flexural strength, indirect tensile strength, California bearing ratio, linear expansion,
durability tests and an analysis of microstructure using (SEM/EDX) and (XRD)
techniques. These assessments aim at determining the treated soil specimens’ properties. The results showed that compressive strength most significantly increases
with an increase in the binder of POFA: MgO containing " (30:10)", reaching values
of 4204 kPa and 5522 kPa in both of the soils after a 90-day curing period. However,
it's worth noting that a notable sharp decline in residual strength was also observed.
Upon the incorporation of polypropylene fibers, the failure mode transitioned to a
more ductile behavior, leading to peak strength values of 4598 kPa and 5878 kPa,
correspondingly. Moreover, the results of the flexural strength have exhibited an
increase in peak behaviour of 1723 kPa, and 2592 kPa, also, tensile strength increased
to 1394 kPa, and 1570 kPa, with an enhancement in post-peak behaviour from brittle
to more ductile in both of the soils. Furthermore, the incorporation of POFA-MgO and
PP fibers resulted in an enhancement of the CBR values for all pre-treated mixtures.
This improvement was reflected in CBR values of 90.71%, 106.92%,163.16%, and
181.26% for MC-B40, MC-B40-R 0.50%, LS-B40, and LS-B40-R 0.50%,
respectively. Meanwhile, the swelling potential of the soil was decreased to
satisfactory values. In addition, satisfactory results were achieved by the optimum mix
in the POFA-MgO-PPF system that withstood twelve Wet-Dry cycles in both soils.
From the microstructural results, the SEM/EDX and XRD analysis demonstrated the
cementitious gel production, such as M-S-H and M-A-H in the samples stabilised with
POFA-MgO. It can, therefore, be concluded that the proposed innovative approach can
generate promising results when applied in the stabilisation of soil.