Improvement of Expansive Soil Property using Rice Husk Ash

This paper discusses the use of rice husk ash as an additive to improve the expansive properties of soil. It explores the method of experimentation and analysis of the results to determine the optimum content of moisture, shear strength, and dry strength. The goal is to achieve soil stability for road construction.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
Improvement of Expansive Soil Property using Rice Husk Ash
By ‘Author Name’
Affiliation (MSc Profile or Track) & Study no.
Executive Summary
Usually, there are geological disasters that occur due to shrinkage and expansion properties with
regards to expansive soil. This paper will be introducing soil as well as its problematic features in
relation when it is mixed with cement. In this paper, there is a proposal of cementitious material
use with a combination of rice husk ash intending to curb the expansiveness of soil used in
paving. The content composes of the method to be used in experimentation as well as the analysis
expected from the results obtained. This would help in projecting the project towards achieving
the project's objectives that include determination of optimum content of moisture, shear strength
and dry strength. These strengths will be investigated against various added proportions of rice
husk ash. In the process, the mixture containing RHA with better mechanical and chemical
properties will be determined through variation of contents proportions to achieve soil stability
before the proposal for use in road construction.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
1. Introduction
Soil
Soil could be defined as one material that exists on the surface of the earth and is that gentle to be
excavated by the use of simple techniques such as shovels and simple machinery (Hall et al.,
2018). Mostly, the soil is made up of liquid, solid and gaseous components formed from
weathered rocks and decomposing plant materials.
Soil Properties
There is a very broad categorical analysis of types of soils hence making soil to be named as one
of the important resources. Mostly, the soil's geotechnical properties are being used in civil
engineering (Han, 2015). The index properties of soil classify soil based on the identified soil
properties. One example of the index classification is the plastic limit, liquid limit and plasticity
index. The liquid limit can be explained to be the content of water in which the soil would change
from a hardened state to a liquefied state. Most soils have small shear strength and at the moment
the water content increases, strength decreases (Laloui, 2014).
Apart from the index properties, other small tests could be done on the soil to help classify soil.
One example of the tests includes analysis via grain size. In soils mechanical analysis, grain size
involves the determination of existent particle size. Therefore, the particle size analysis could be
done in two types;
 Through wet sieving that generally involves hydrometer tests, this test is mostly used in
analyzing fine particles.
The formula for getting the particle size is:

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
(Nelson et al., 2015)
Where M composes of;
(Nelson et al., 2015)
In this equation, represents the poise viscosity of water, represents the solid
specific gravity, represents the density of water in gm/ml, while represents the
effective depth. The time is represented by t which is in minutes.
For percentages finer than the size D, the format used is as follows;
(Nelson et al., 2015)
In that R represents the corrected reading of the hydrometer while Ms represents the dry
spoil’s mass in 1000ml suspension.
 Through dry test that involves sieving whereby the particles analyzed have to be coarse.
 Through the compaction test that involves conducting a test to determine the optimum
moisture content as well as the dry density in specified soil samples.
The compaction test uses the following formula in determining the dry soil's density.
(Nelson et al., 2015)

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
Whereby, M represents the soil’s total mass, V represents the soil’s volume and W
represents the content of water. The test is conducted using the standard proctor device
assembled as shown below;
(Nelson et al., 2015)
(Nelson et al., 2015)
 When one intends to measure the compressive soil strength, the tri-axial compression test
is done.
Soil Expansiveness
Most buildings are erected with foundations which are poor due to bad soil conditions existent in
the site. However, due to the absence of suitable land, homes are forced to be erected in marginal
lands which are features by insufficient load-bearing capacity. Hence, the ground cannot support
the structures to be built. The land is generally becoming scarce and as a result, developing cities.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
This is influenced by the need to build more structures and other buildings on various sites given
the bad state at present (Dhir, et al., 2018).
The tendency of some soils to exhibit expansiveness is one problem experienced in most civil
engineering applications. Mostly, it depends on the presence of soil interacting with water. When
there is a change in the volume of soil, there could be significant damages to structure with the
lightweight. For example, cracking could occur on walls in single-story buildings, the pavements,
as well as the pipelines, could be distorted. There are numerous additives that are being used in
treating expansive soils. For example, surfactants, lime, polymers, salt, fly ash and other mixtures
made up of a mixture of these mentioned additives. Lime, on the other hand, is the commonly
used treatment technique since it has the ability to improve the soils mechanical properties other
than the expansiveness. In addition, lime is abundant and is economical in various parts of the
world (Mustansar, 2019). Usually, lime is used as an additive reacts with the particles in the soil
and reduces the potential of swelling while it adds the durability and strength of the soil.
Numerous studies have been done on the literature to explain the improvements I hydraulic and
mechanical properties of soil expansiveness by means of adding stabilizers (Han, 2015). These
sites have majored on the microscopic views. Most researchers are focusing on studying the
changes that associate with the Atterberg limiting values. These values include the liquid and
plastic limits other than looking into other soil properties such as change in volume (these include
the swell potential, swell pressure and heave) permeability coefficient and shear strength in
expansive soils.
On the other hand, there is a late tendency of using recycled materials to reduce the volume of
landfill areas other than opening the gate for sustainable building engineering practices
applications. This article will be focusing on presenting a proposal on conducting a laboratory

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
experiment which intends to investigate the feasibility of using waste material such as rice husk
ash. The rice husk ash is proposed due to its ability to improve the consistency and strength of
expansive soils. Other geotechnical properties studied are in relation to soil index properties that
includes plastic limit, liquid limit, strength and free swell index features in stabilized soils once
there is the use of waste material in replacing portions of the soil mixture.
2. State-of-the-art/Literature Review
Aziza et al. (2018) used rice husk ash, gypsum and lime as the additives in soil exhibiting
expansiveness and this led to the consideration that the strength of soil improves with the addition
of additives. In this experiment, it was identified that rice husk ash could potentially stabilize
soils with expansiveness, solely or when mixed with gypsum and lime. The industrial waste is
being utilized in this paper, the RHA, gypsum and lime, as alternatives hence reducing the cost in
making roads, specifically in remote areas. In the observations, the expansive soil's liquid limit
had been lowered by 22% in the portion having 5% lime and 20% RHA. The free swell index
was able to be lowered by 88% in a mixture having 5% lime and 20% RHA. The expansive soil's
unconfined compressive strength was able to be heightened by 548% in an addition of 5% lime,
20% RHA and 3% gypsum once the sampled was cured for 28 days.
Saljnikov and Cakmak (2016) experiment was on the use of stabilized soils using rice husk
additives. In this test, the classification of index properties was as (A-76) as seen in the AASHTO
scheme for classifying soil. The geotechnical and index properties tests performed on the soils
samples having rice husk ash and lime combinations led to the identification that soils rid with
plasticity could be significantly improved from the 18.10 to 6.70 as was seen in sample A while
in sample B the results was 26.6 to 5.92 using 12.5% RHA and 65% lime. Looking at the
compaction features, the rice husk ash and lime addition led to a reduction in dry density and an

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
increase in moisture content. The 12.5% RHA and 8% lime had their MDD values in samples B
and A were 1.22 and 1.27 Mg/m respectively. There was California bearing ratio peaking 50%
with 8% unsoaked values in lime while the RHA was 10% when considering sample A. in
sample b, there was a 12.5% RHA, 30% California bearing ration and the used lime was 6%. In
this paper, the results showed that the experiments had three different soils that were improved on
their soil properties through the addition of rice husk ash.
Reiniger (2017) produces a trivial improvement on soil expansiveness with regards to
construction material when the rice husk ash together with fly ash was used, these were the waste
materials considered. The expansive soil was blende fly ash and RHA and later strength tests
were performed. The fly ash-RHA potential in a swell reduction in the foundation footing and
subgrade was then studied. In the determination of the study's importance, the cost was compared
with regards to the preparation of a highway project's sub-grade without and with admixture
stabilization. The behaviour of noted in the stress-strain of the unconfined compressive strength
exposed the failure of the strain and stress that read 50% and 106% respectively when the there
was an increase of fly ash by 25 %. In case there was an increase in the RHA from 0 to 12%, it
led to a 97% increase of unconfined stress and the CBR rose by 47%. Hence, the 12% RHA
content together with the 25% fly ash content was seen to be the recommended quantity to
produce an improved strength within the subgrade expansive soil. 15% of fly ash content was
recommended to be blended with RHA in case the soil needed its well to be reduced to a
satisfactory value.
Kallel et al. (2018) experiment made a presentation of a laboratory experiment that studied black
cotton soil whose property was highly expansive. The study involved stabilization using rice husk
ash and fly ash. To begin with, the soil samples were taken from the known road within a rural

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
setting in Raipur region. This soil was taken through various processes off mixing components to
make it stable. The various FA percentages were 15, 12, 10, 8 and 5%while the various RHA
percentages were 15, 13, 11, 9, 6 and 6%. The specific gravity, Atterberg limits, unconfined
compressive strength and California bearing ratio tests were conducted on the soil stabilized
samples and raw samples. The experiment's results showed that addition of RHA FA led to a
reduction of plasticity index as well as the soil's specific gravity.
McCartney and Hoyos (2018) produced an experiment that conducted studies on soil
expansiveness with an addition of gypsum, lime and RHA properties on the soils expansiveness.
The experiment involved the following studies; compaction, Atterberg's limits, CBR, strength
and free swell indexes. In the observations, the expansive soil's liquid limit had been lowered by
a 20% drop while the free swell was able to reduce by 88% once the RHA proton of 20%, 3%
gypsum and a 5% lime were added.
Khalili et al. (2014) also studied the effect of blending the RHA and cement mixture on the soil
expansiveness properties for example dry density, moisture content, unconfined compressive
strength and CBR. The paper was studying soft soil. This had the CBR value reading 1.46 while
the UCS was reading 70KN/m2. Looking at this soil, its properties were representing high
expansiveness. However, the sil had to be used in construction purposes. Hence, it had to be
stabilized. Once the study was through, the revealed content was the ability of the RHA
proportion together with a cement percentage had a 10% decreasing effect on the maximum dry
density as well as increasing the moisture content to 15% when the RHA was being increased.
Additionally, the CBR value was 106% when the RHA content was 10% compared to the 10%
RHA. This was reading a 90.6% improvement on soil expansiveness s reduction. To attain

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
maximum strength improvement, the soil was stabilized using 10% RHA and an additional
cement at 6% portion for practical uses.
Deepak et al. (2016) conducted an experiment on the dry density whereby there was a maximum
acquired dry density while the content of moisture increased with the addition of rice husk ash. In
this scenario, rice husk ash had lowered the dry density of the soil to 2.69 since it filled the voids
between the soil particles. Regarding unconfined compressive strength, the soil was mad
adaptable to additional load. The increase of RHA from 0% to the maximum 20% led to a
decrease in UCS when the samples were tested on the 7, 4 and 28 day of curing. The UCS was
decreasing sharply.
Singh et al. (2018) recently determined numerous waste materials which have been applied in soil
stabilization so that to minimize both the need for outdated additives including cement and lime
and environmental challenges. Rice husk powder and rice husk ash are agricultural remains and
waste materials extracted from outer most covers of rice grains during the process of milling.
Rice husk ash such as large quantities of silica containing huge specified surface which is the
most preferred for activating lime and soil reactions.
Agnihotri (2014) Outlines that the inclusion of lime at 6% combined with RHA in principle have
a critical impact in the reduction of swelling pressure and swelling of soils (Shehata & Poulos,
2018)on the other hand is of the opinion that the specimen’s unconfined compressive strengths
increase with the inclusion of RHA and lime in soils. Whereas the application of lime boosts the
many engineering features of soil, it results in bad phenomena including minimized axial strains
after peak strengths, plasticity and residual strengths in soils. Recently, polypropylene fibres are
being included in soils in order to boost the ductility, swelling and strengths properties of soils.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
3. Research Question, Aim/Objectives and Sub-goals
Research Question Relevant Hypothesis
Q1 Could soil structure be a risk in
construction?
H1 Construction sites are vulnerable risk from
soil structures
Q2 If so, what could be the risk encounters
in the field?
H2 Risk occurs due de-stabilized soil structures
such as sodic, alkaline and acidic soils
H3 Risk occurs due to vulnerability to sulphate
attacks
H4 Risk occurs due to poor proportional
inclusion of additives such as cement
Q3 In a building professional’s perspective,
what could be the effective method for
curbing the risk?
`H5 Accurate proportional inclusion of soil
additives
Q4 Do the instruments used in soil provide
performance advantages?
H6 Soil could be improved through
stabilization through additives such as rice
husk ash, lime as well as other additives
present.
Objectives of the study
a. To find out the optimum content of the moisture, shear strengths and highest dry densities in
respect with first samples with no additives.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
b. To find out the highest dry densities, shear strengths, and optimum contents of moisture in
respect with percentages of cement additives and rice husk ash to the soils and determine the
maximum percentage.
c. To give a comparison between the obtained results of the initial samples and the optimum
samples containing admixtures.
4. Theoretical Content/Methodology
MATERIALS
Expansive Soils
This research will involve picking of expansive soils that have been dried in the air. Expansive
soils should be crushed to form particles then later sieved using a 10mm sized sieve. The swelling
capability, specific gravity, compaction properties, moisture content limits and free swelling
ratios should be conducted and listed. The chemical components of expansive soils should also be
tested.
Rice Husk Ash
RHA shall be extracted from biomass-powered plants. The RHA should be averagely thick while
its linear surfaces should be thin. The outer and inner surfaces should be sandwiched. These
interlayers should consist of plates that are crisscrossed and arranged in the same direction to
form structures that resemble loose honeycombs. If sheets enlarge further, it will be an indication
that sheets have very many holes (Shah, et al., 2015). These holes are known as honeycomb
holes which should consist of scales ranging from 5 to 10 μm. Therefore, rice husk ashes are
basically materials that are porous and contain huge surface areas. The rice husk ashes should be
ground. Then after being ground samples should be filled immediately in bags which are sealed

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
and stored. Analysis of particle sizes and specific surface areas of RHA should be tested as well
the chemical constituents of RHA tested.
Lime
The lime to be used is the hydrated lime powder which shall be obtained from a lime plant
locally. It is important to check the chemical constituent of the lime.
Experiment techniques
The experiment shall be divided into two main sections. In the first one, lime and RHA mixes
will be used as cementing components. The ratios of lime and RHA will be determined in regards
to the outcome after testing the strength of the mortar. In the second part, RHA –lime will be
used as stabilizers then mixed with expansive soils. The impacts of the quantity of lime to RHA,
time, water contents at the beginning on the deformation and strength and curing features of the
solidified soils will be studied.
5. Experimental Set-up
How to prepare materials for the experiment
RHA, expansive soils and lime should be dried, ground and sieved using various sieves.
Ratios between Lime and RHA using mortar tests
For better samples to be obtained, the lime and rice husk ash ratios, six sample proportions must
be designed. Moulding, mixing and compaction should be performed in respect with
requirements of testing cement mortars. Specimens should be retained in the cutting chambers at
a humidity of 95% and curing temperatures of 200 C. testing should be conducted at seven,
fourteen, twenty-eight and fifty-six days respectively. Curing duration should be elongated so as
to enable enough time for the pozzolanic to react. The appropriate ratios between lime and RHA
shall be acquired after the strengths among the 6 samples of the mortars have been compared.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
Tests
For the impacts of the lime and RHA ratios on expansive soils that have undergone stabilization
to well understood, it is important to conduct the following tests;
 Swelling tests such as swelling pressure and swelling capability
 The distribution of the size of the grain
 Consolidation tests
 Direct shear tests
 Unconfined compression tests
 Observing the development of cracks
6. Results, Outcome and Relevance
The strengths and deformation features of stabilized expansive soils should be determined
through the consolidated tests, swelling tests, direct shear tests, unconfined compression tests and
many other tests. With the inclusion of curing time, the amounts of lime and RHA and
deformation characteristics such as the swelling pressure, swelling capability, compression index,
fineness and amounts of cracking in regards to the expansive soils should be performed.
Additionally, the strength features including cohesion, compressive strengths and the inner angles
of friction should be substantially enhanced.
Putting into account the engineering workability and amounts of water, costs, optimum moisture
and mix proportions are suggested in the stabilization of expansive soils. Moreover, the RHA and
lime effectiveness in the stabilization of expansive soils must be evaluated for viability by
analyzing ion exchange, coagulation reactions and replacement efficiency.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
7. Project Planning and Gantt Chart
8. Conclusions
This paper looks at the three major objectives, first, how soil properties should be improved at
construction sites. The improvements should be done to prevent the soils from bending when
subjected to pressure resulting from the weights of constructing structures. Secondly, how
excessive consumption of cement can be minimized with an effort of substituting with other
materials that can deliver the same work. The given materials should be able to be recycled
because their presence on the environment might cause harm to the environment (Hashim &
Bakar, 2015). These material wastes also cover huge areas in landfills an example of such
materials is called rice husk ashes as outlined above in this paper. This paper also gives a review
of the literature and research that should be conducted so as to utilize the rice husk ash to boost
deficient soils through stabilization. Generally, the review reveals the abilities wastes from
agriculture that can be applied to improve the geotechnical features of soils that are deficient.

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
This implies that the application of these materials in practising geotechnical engineering on a
large scale should aid in achieving durable and stable buildings. Thus, the steps suggested above
for the rice husk ash experimentation and analysis in the soil stabilization (Nicholson.P.G., 2014).

Student’s Name, 2019, Improvement of Expansive Soil Property using Rice Husk Ash
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