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Strength Analysis of Heat Treated Clay and Rice Husk Mixture

Ettah E., B, Ekpo, C. M, and Ishaje M. E

Department of Physics, University of Cross River State – Nigeria

DOI : https://doi.org/10.51583/IJLTEMAS.2024.130505

Received: 28 February 2024; Accepted: 20 March 2024; Published: 08 June 2024

Abstract: The strength analysis of Heat Treated Clay and Rice Husk Mixture was to ascertain the threshold temperature and the

strength of the sample for construction work. The strength of the material was analysed to determine the threshold temperature to

produce a satisfactory construction material from Rice Husk Ash and clay. The materials used in this study include rice husk,

clay, sieve shaker kiln, mould, muffle furnace, compression machine and Schmidt hammer. The rice husk was collected from the

rice mill and dried under the sun and burnt in kiln at the temperature of 500

Celsius to 700

Celsius to become white grey and

sieved with sieve shaker 15m to obtain smooth and fine ash and mixed with clay in different ratios of 500 : 500, 600 : 400, 700 :

300, 800 : 200 and 900 : 100 in grams, ash and clay respectively, and the mixture was introduced into moulds and was taken to

unconfined compressive machine to determine the untrained strength and the stress-strain characteristic of the sample after that,

the samples was left for four days to dry under room temperature and weigh before it was heated in the furnace to ascertained the

rate of water moisture in each of the samples. From the furnace, the samples were reweighed to ascertained the water contain if at

all there is, and at what rate. Schmidt hammer was applied for impact test in mega paschal (Mpa) after heating. It was noticed

that the mixture ratio of 900g ash: 100g clay gave the optimum strength for building and construction work. From the test results,

compressive test sample E with the mixture of 900g ash and 100g clay shows that crushing load of 30.46Kn, strength of the

material proves to be 3.33Nmm

, density of the material is 1245gm

, impact test result 22.7Mpa.

Keywords: Rice Husk, clay, strenght analysis, crushing load, material

I. Introduction

The construction industry is continuously seeking innovative and sustainable materials to meet the demands of modern

infrastructure development while minimizing environmental impact. One such avenue is exploring the potential of clay-based

materials and agricultural waste byproducts. This research proposal aims to investigate the strength properties of a composite

material composed of heat-treated clay and rice husk mixture, with the goal of understanding its feasibility for structural

applications. Davidovites, (2020).

Rice husk are the heard protecting covering of grains of rice in addition to protecting rice during the growing seasons. Rice hulls

are part of the chaff of the rice. Rice husk can be put to use as building materials, fertilizer, and insolation material or as fuel. Lee

et al, (2008).

Rice husk (RH) is a residue generated during the rice production. The main problem related with this residue it’s that exists in

large quantities leading to management problems, as well as its high volume. After incineration, it is obtained only 20 wt% of rice

husk ash (RHA) but has a high silica content. This high silica content makes the residue very interesting for a variety of different

applications. The understanding of the influence that the thermal and chemical treatments have in the properties and silica content

of the RHA is crucial. Neville, (2020).

The primary objectives of this research are as follows:

 To assess the effect of incorporating rice husk into clay and subjecting the mixture to heat treatment on the strength

properties of the composite.

 To determine the optimal mixture proportions of clay and rice husk for achieving desirable mechanical strength.

II. Literature Review

According to Pius, (2017); Clay bricks are more popular in building constructions than the cement/concrete bricks because of

Eco-friendly and low cost. These bricks have been made from clay, since they found. However, the quality of the bricks can be

upgraded by doping with the agricultural natural waste materials. Rice husk (RH) is a most common and hugely abundant wastes

that consist of SiO2 percentage is RHA. In the present study, eight sets of brick were manufactured and each set consists of three

bricks. These bricks were doped with RHA of ratio 0 to 30% of the total weight of mixture with a step of 5%. These bricks were

allowed to dry for 3 days and fired in the brick kiln, which the traditional method is still used to burn bricks in Sri Lanka. The

physical and mechanical properties of the burnt bricks were tested and compared with Sri Lankan Standard Specifications (S.L.S)

as well as the British Standard Specifications (B.S.S) and compared with the commercially available brick made purely from clay.

The bricks doped with RHA are obviously superior to the commercially available brick in the Eastern region of Sri Lanka.

However, the brick doped with 5% RHA has higher compressibility of 3.7 N.mm -2 and the water absorption of 15.8% that

satisfy the S.L.S and B.S.S.

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Subashi (2021) investigated effect of waste RHA, residual ash generated from rice husk fuelled brick kilns, on strength, durability

and thermal performances of mortar was investigated. Cement in the mortar was replaced by 0%, 5%, 10%, and 20% of waste

RHA. Compressive strength, bulk density, water absorption, porosity, sorption rate, sulfate, acid and alkaline resistance, thermal

performance, and microstructural analysis of specimens were examined. Bulk density of control (i.e. 0%) and 20% waste RHA

mortar were 2033 kg/m

and 1821 kg/m

, respectively, promising a lightweight mortar by blending waste RHA into the

mixture. At 56 days, Strength activity index (SAI) was achieved to be 95% and 85% for 5% and 10% waste RHA mortar,

respectively, indicating better compressive strength achievement with waste RHA added mortar. The expansion due to sulfate

exposure was reduced by 54% and 70%, for 5% and 10% waste RHA mortar, respectively. Weight loss due to acid exposure was

reduced by 45%, 40%, and 25% for 5%, 10%, and 20% waste RHA specimens, respectively. The weight loss due to alkaline

exposures was reduced from 3.13% to 2.41% with rising waste RHA level from 0% to 5%. Mortar with 20% waste RHA had a

higher temperature difference than the control mortar, indicating that RHA contributed to the reduced thermal conductivity. At

5% waste RHA sample, high counts of CSH was formed, micro-voids were filled, making it a dense structure, which is favorable

to achieve improved strength and durability performances.

Pornkasem et, al. (2018) investigated the potential and efficiency of the use of Rice husk Ash (RHA) to add up partially which

replaced Portland cement in deep cement mixing technique are examined. A series of unconfined compression tests on cement -

RHA-stabilized clay was conducted to investigate the influence of RHA on the mixture properties. Special attention also was paid

to its efficiency for increasing the strength by partial cement replacement to obtained high strength soil cement, and also it was

compared with fly ash. The tested result indicated that up to 35% of RHA could be advantageously added up to enhance the

strength if the cement contain in the mixture is larger than 10%. The RHA enhanced the strength of cement-admixed clay by

larger than 100% at 28 days. For curing time of 14 and 28 days, the RHA exhibited higher efficiency on Portland cement

replacement when the cement and overall cementations contents are not less than 20 and 35%, respectively. The optimum

condition for high strength mixture is achieved with addition of RHA of about 20% cement content mixture. When compared

with fly ash of similar grain size, the efficiency of RHA is higher when the content added is greater than 15%. This indicates the

suitability of RHA for used in high-strength soil-cement.

Joel, 2011 investigated the effect of rice husk ash (RHA) on the burnt properties of the clay brick 2 to 10% RHA was blended

with the clay. Atterberg limits specific gravity, compressive strength and water absorption test were conducted on each

admixture. In addition, X-ray diffraction and geochemical tests were performed on the soil and rice husk ash respectively. X-ray

diffraction studies shows that the Ibaji soil was mainly kaolinite. The results showed that the plasticity index reduced gradually

and had a minimum value at 6% RHA. The compressive strength and water absorption attained a maximum value of 18.64MN/m

and a minimum value of 14.8% respective at 2%RHA additive led to a significant improvement in the properties of Ibaji burnt

clay brick.

2.1 Theoretical Background

This study is material science which is a branch of solid state physics. Materials science is interdisciplinary field where other field

of studies are combined together. The termed materials science and engineering, covers the design and discovery of new

materials, particularly solids. The intellectual origins of materials science stem from the Enlightenment, when researchers began

to use analytical thinking from chemistry, physics, and engineering to understand ancient, phenomenological observations in

metallurgy and mineralogy. Hegazy, (2012). Materials science still incorporates elements of physics, chemistry, and engineering.

As such, the field was long considered by academic institutions as a sub-field of these related fields.

2.2 Shear Modulus of Rigidity

Shear modulus also known as Modulus of rigidity is the measure of the rigidity of the body, given by the ratio of shear stress to

shear strain. Often denoted by G sometimes by S or μ.

Shear Modulus of elasticity is one of the measures of mechanical properties of solids. Other elastic moduli are Young’s modulus

and bulk modulus. The shear modulus of material gives us the ratio of shear stress to shear strain in a body.

Shear modulus formula:

Txy





F A Fl

x l x







 



(1)

Where :

T= T x y F/A = Is the shear stress

F= force acting on the object

A is the area on which the force is acting

Y x y ∆x/l is shear strain.

Bulk modulus is a modulus associated with a volume of strain when a volume is compressed.

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The formula for bulk modulus is bulk modulus = -(pressure applied /fractional change in volume)., where

K= bulk modulus

P = pressure

V = initial volume of the substance



(2)

Bulk modulus is used to measure how incompressible a solid is. Besides, the more the value of K for a material, the higher is its

nature to be incompressible. The unit of bulk modulus is the same as that of pressure N/M

The reciprocal of Bulk modulus is

called compressibility

Young modulus =

longitudinalstress

longitudinalstrain



F A FL

l L la



(3)

The unit for young modulus is Y = N/M

Mechanical Testing: Conduct comprehensive mechanical tests on the heat-treated composite specimens, including:

 Compressive Strength (σ

): The compressive strength of the composite will be determined using the formula: σ

= AP.

Where P is the maximum load applied and A is the cross-sectional area of the specimen.

 Tensile Strength (σ

): The tensile strength will be calculated using the equation: σ

Where F is the maximum tensile

load applied and A is the cross-sectional area.

Source: [kedsarin, (2001); Kute, (2003); and Dondi, (2009)]

3.0 Materials

The following materials were used in the study

i. Rice husk ash

ii. Clay

iii. Sieve Shaker

iv. Kiln

v. Mould

vi. Weighing Balance

vii. Muffle furnace

viii. Unconfined compression machine

ix. Compression machine

x. Schmidt hammer

III. Method

Rice husk used for this study was collected from Akpet rice mill in Biase Local Government Area of Cross River State Nigeria.

The rice husk was stacked in heaps near the mill. Samples were collected from different spots at the heap site. The sample were

dried under the sun.

The rice husk was burned at 700

C for 6 hours in a kiln. The ash was left to cool inside the kiln and removed the next day. The

ash was then sieved using sieve shaker of a 150µm to achieve a degree of fineness of the sample (RHA) was weighed with the

weighing balance in the ratio of 500 :500, 400 :600, 300 : 700, 200 :800, and 100g clay: 900g Ash respectively into five different

portions and the sample was mixed with water for moulding and was taken for compression with unconfined compression

machine to ascertained the shear stress and strain.

The sample was weighed to ascertain the weight of the sample and kept for solidification 4 days in room temperature after that

the brick was put in a muffle furnace for a temperature between 900 – 1200 degree Celsius to achieve crystalline like nature

(vitrification). The brick was left in the furnace to cool the next day it was removed weighed after heat to ascertain its weight

before exposed to impact factor test and compression test to ascertain the hardness of each of the samples.

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IV. Results and Discussion

4.1 The table below shows the result of Compression test. Cylindrical shape Dimension of the sample, height 9cm, and diameter

5cm The sample was measured in gram ratio Ash and clay

Area of a cylinder, A=



(4)

Volume of a cylinder, V =



(5)

Density of the sample, ,

where D = density (6)

Strength of the sample, stress =

load

Area

(7)

Table 4.1: Compressive Test Results

Mixed samples

Weight of sample

before dry (g)

Age

(days)

Weight of sample

after dry (g)

Density

(g/m

)

Crushing load

(KN)

Strength

N/mm

500g ash 500gclay

250

4 days

132

0.746

3.32

1.69

600g ash 400gclay

258

4 days

129

0.739

2.52

1.28

700g ash 300gclay

264

4days

110

0.621

4.10

1.87

800g ash 200gclay

300

4 days

199

1.000

7.88

2.09

900g ash 100gclay

340

4 days

275

1.245

30.46

3.33

A B C D E

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Strength N/mm

Samples (g)

Fig.4.1. The bar chat shows the strength of the sample

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V. Discussion of the Results

From table 4.1 compressive test result of the crush load, the strength and the bulk density of different samples were determined

based on the mixture ratio of each sample A, B, C, D and E with 900g ash: 100g clay, shows high strength of the material with

30.46 kN, 3.33Nmm

and 1245g/m

. The test result shows that pozzolans can complement ordinary portl and cement for building.

From the bar chart shown in figure 4.1, that shows the strength of the material, sample E has the highest strength followed by

sample D. Then C and A. With this result, pozzolans can substitude Portland cement for construction of culvert and pavement in

general the optimum of the material is ascertained. With the mixture of 900g ash and 100g clay.

From the findings, it is observed that pozzolans of this mixture 900g ash and 100g clay which the unit strain

and stress of the sample prove that it can replace Portland cement for construction work and also shows the optimum strength of

the material for construction of concrete. The percentage or ratio of mixture of the sample shows that addition of RHA to clay

gives high strength of the material which is suitable for building and construction.

VI. Conclusion

The analysis of heat treated clay and Rice Husk mixture can sub stitude the ordinary Portland cement for building and

construction works with the strength sample of 900g ash and 100g clay as shown. Secondly Rice Husk Ash with clay of this

mixture can withstand load in term of strenght. The outcomes of this research provides valuable insights into the feasibility of

utilizing such composites in structural applications, leading to more eco-friendly and efficient construction practices.

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