GREEN CONCRETE DEVELOPMENT: INVESTIGATING THE

COMPRESSIVE STRENGTH OF COCONUT SHELL ASH, RICE HUSK

ASH, AND RED CLAY

JOHN LERIE DIMAANO

ELLAJEN M. OPADA

FEBE P. RICO

JUNE 2025
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Chapter 1

INTRODUCTION

1.1 Background of the Study

Concrete serves as a foundational material in modern construction, playing a

crucial role in infrastructure development worldwide. However, its production poses

substantial environmental challenges, including the depletion of natural reserves, high

energy demands, and significant carbon emissions. The cement industry alone

accounts for approximately 7-8% of global CO₂ emissions, making it a major

contributor to climate change (Al-Otaibi, 2024). To mitigate these impacts,

researchers and engineers have focused on sustainable alternatives such as green

concrete, which integrates waste materials to replace conventional cement and

aggregates. This innovative approach not only reduces environmental damage but also

enhances the material’s durability, resilience, and overall performance, leading to

more sustainable construction practices.

As the global shift towards eco-conscious solutions gains momentum, green

concrete has emerged as a viable answer to the pressing issues of resource depletion

and carbon emissions. Defined as a concrete mix containing at least one sustainable

ingredient, green concrete is formulated using industrial byproducts, agricultural

residues, or other recyclable materials that offer environmental benefits without

compromising structural integrity (Hashmi, Khan, Bilal, Shariq, & Baqi, 2022). The

adoption of green concrete is not merely a substitution of materials; it represents a

paradigm shift in construction methodologies, embracing sustainable design

principles that aim to optimize resource efficiency while maintaining long-term

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viability. Commonly used green concrete components include fly ash, blast furnace

slag, and silica fume, all of which have been widely studied for their pozzolanic

properties, contributing to improved concrete strength and durability (Al-Otaibi,

2024). The benefits extend beyond material composition, influencing building

techniques, economic feasibility, and environmental conservation within

contemporary infrastructure.

One of the most promising developments in sustainable concrete technology is

the integration of agricultural residues, which has garnered attention due to its

potential for large-scale waste utilization. Agricultural byproducts such as rice husk

ash (RHA) and coconut shell ash (CSA) offer substantial advantages when

incorporated into concrete formulations (Mahato, Kumar, Thereja, & Rana, 2022).

Rice husk ash functions as a pozzolanic additive, enhancing concrete’s porosity

control, impermeability, and sulfate resistance, while simultaneously addressing

environmental concerns related to the widespread burning of rice husks. Meanwhile,

coconut shell ash provides a viable aggregate alternative, displaying high resistance to

crushing and impact forces due to its unique surface texture, which improves concrete

workability (Sujatha & Balakrishnan, 2020).

Another material gaining attention in sustainable construction is red clay,

known for its high clay mineral content and variable structural behavior influenced by

moisture conditions. In arid environments, red clay exhibits strong load-bearing

capacity, while in wet climates, it is prone to differential settlement challenges (Lu,

Yu, Xu, Yue, & Sheng, 2023). Research has shown that cement incorporation can

improve the cohesion and bonding characteristics of red clay, making it more

adaptable for construction applications where stability is crucial.

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Given these promising prospects, this study systematically evaluates the

effects of coconut shell ash, rice husk ash, and red clay as alternative materials in

concrete mixtures. It aims to determine their influence on mechanical strength,

durability, and environmental impact, providing comprehensive insights into the

feasibility of integrating agricultural and industrial byproducts into sustainable

construction practices. By analyzing the physical and chemical properties of these

materials, this research seeks to advance knowledge in eco-friendly concrete

innovations, contributing to a future where infrastructure development aligns with

environmental conservation.

1.2 Statement of the Problem

Concrete is one of the most widely used construction materials globally due to

its strength, durability, and adaptability to various structural applications. However,

the production of traditional concrete relies heavily on non-renewable natural

resources and contributes significantly to carbon dioxide emissions, raising both

environmental and economic concerns. As the construction industry moves toward

more sustainable practices, it becomes imperative to explore eco-friendly alternatives

that reduce the environmental footprint without compromising performance. This

research aims to investigate the potential of green concrete by partially replacing

conventional cement with sustainable agricultural and natural waste materials—

specifically coconut shell ash (CSA), rice husk ash (RHA), and red clay (RC). More

specifically, the study aims to answers the following questions:

1. What are the physical and mechanical properties of:

a. Coconut shell ash

b. Rice husk ash

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c. Red clay

2. What are the mechanical characteristics of concrete when mixed with:

a. 0% CSA, 0% RHA, and 0% RC (control)

b. 10% CSA, 25% RHA, and 5% RC

c. 10% CSA, 20% RHA and 5% RC

d. 5% CSA, 15% RHA and 5% RC

3. How is the compressive strength of concrete with CSA, RHA and RC

compared to conventional concrete at 7, 14, and 28 days of curing in the

designing of slab?

1.3 Objective of the Study

The main objective of this study is to utilize green concrete to reduce the

environmental impact of construction by incorporating sustainable materials,

minimizing carbon emissions, and promoting the use of industrial waste products

without compromising structural performance. Specifically, this study aims to:

1. . To assess the physical characteristics of:

a. Coconut Shell Ash

b. Rice Husk Ash

c. Red Clay

d. Moisture Content

e. Particle Size Distribution

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2. Analyze concrete mixtures using various proportions of CSA, RHA and RC

(Mix B - 10% CSA, 25% RHA, and 5% RC), (Mix C - 10% CSA, 20% RHA

and 5% RC), (Mix D - 5% CSA, 15% RHA and 5% RC) as partial cement

replacements and examine the compressive strength of concrete specimens

cured for 7, 14, and 28 days.

3. Identify the blend ratio of CSA, RHA and RC that yields the highest

compressive strength.

1.4 Scope and Limitations

This study examines the compressive strength of concrete with Coconut Shell

Ash (CSA), Rice Husk Ash (RHA), and Red Clay (RC) as partial cement substitutes.

The concrete samples contain 10% CSA, 25% RHA, 5% RC, 10% CSA, 20% RHA,

5% RC, and 5% CSA, 15% RHA, and 5% RC, as well as a control mix with no

additives. Testing at 7, 14, and 28 days after cure assesses strength progression. This

study seeks the best mix of compressive strength and sustainability. Compressive

strength is the only mechanical attribute tested in this lab-scale investigation.

Tensile, flexural, permeability and long-term durability are ignored. The study ignores

cost analysis, field implementation issues, and extreme environmental performance.

Material availability for CSA, RHA, and RC varies by region.

1.5 Conceptual Framework

Figure 1 presents the conceptual framework of this study, highlighting the

interconnections between the main variables in evaluating coconut shell ash, rice husk

ash, and red clay as a partial replacement of cement. It depicts the inputs, processes,

and outputs involved, illustrating the assessment of coconut shell ash, rice husk ash,
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red clay for their structural performance, cost efficiency, and environmental impact.

This framework serves as a guide for the research methodology, ensuring a structured

evaluation of the material's feasibility when compared to traditional insulation

alternatives.

Input Process Output

Materials Preparation Physical and Mechanical

Cement, Fine Aggregates, Collection and preparation Properties
and Coarse Aggregates of materials (CSA, RHA, Physical Properties of
Coconut Shell Ash (CSA), and RC) Coconut Shell Ash, Rice
Rice Husk Ash (RHA), Husk Ash, and Red Clay
Red Clay (RC) Mixing Compressive strength of
Mixing base on the four concrete mixtures at 7, 14,
Concrete Mixes specified concrete mixture and 28 days
Mix 1: 0% CSA, 0% RHA, designs
and 0% RC (control) Casting 48 concrete Optimal Mixture
MIx 2: 10% CSA, 25% samples into molds Identification
RHA, and 5% RC Curing samples for 7, 14, Determining the most
Mix 3: 10% CSA, 20% and 28 days under effective mixture for
RHA and 5% RC controlled conditions enhancing concrete
Mix 4: 5% CSA, 15% properties
RHA and 5% RC Testing Assessing the synergy
Physical and Mechanical between CSA, RHA, and
Test Conducted Properties of CSA, RHA, RC
Physical and Mechanical and RC
Properties of CSA, RHA, Compressive Strength Sustainability Insights
and RC Contribution to sustainable
Compressive Strength construction by
incorporating waste
Curing Periods materials into concrete
7, 14, and 28 days production

1.6 Significance of the Study

This research contributes to sustainable construction practices by offering an

alternative to cement-intensive concrete production. By utilizing agricultural waste

such as CSA, RHA and RC, the study aligns with circular economy principles and

reduces environmental degradation. The study may benefit:

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1. Construction professionals, by introducing viable, eco-friendly concrete

alternatives.

2. Environmental policymakers, by supporting green infrastructure initiatives.

3. Academic researchers, through added insight into pozzolanic materials and

sustainable concrete technologies.

4. Local communities, by providing opportunities for value-added use of

agricultural residues.

1.7 Definition of Terms

To better understand the study, the following terminologies are operationally defined.

Green Concrete. Environmentally friendly concrete that includes recycled or

waste materials to reduce ecological impact.

Coconut Shell Ash (CSA). A pozzolanic material obtained from the

controlled combustion of coconut shells.

Rice Husk Ash (RHA). A silica-rich by-product of controlled rice husk

burning, valued for its high pozzolanic activity.

Red Clay (RC). A fine-grained, reddish soil rich in iron oxides, known for its

low permeability and plasticity, commonly found in tropical areas.

Compressive Strength. The ability of concrete to withstand axial loads

before failure.

Pozzolanic Material. Siliceous or luminous materials that react chemically

with calcium hydroxide in the presence of moisture to form cementitious compounds.

Ordinary Portland Cement (OPC). The most commonly used cement in

construction, known for its high carbon footprint.

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Carbon footprint. This term refers to the total amount of greenhouse gases,

including carbon dioxide, that are emitted because of human activities.

Carbon dioxide (CO₂). Emissions of carbon dioxide arise from the

combustion of fossil fuels and the production of cement, encompassing CO₂

generated from the consumption of solid, liquid, and gaseous fuels, as well as from

gas flaring.

Curing. This process involves maintaining moisture in concrete to ensure it

attains the desired strength and durability.

Durability. This term denotes the capability of materials, structures, or

products to endure various stresses, environmental factors, and wear overtime without

experiencing significant degradation.

Physical properties. These are characteristics of matter that can be observed

and measured without altering the substance's identity.

Pozzolana. It is an ash-based alternative to cement, comprising siliceous and

aluminous minerals that help decrease the production of ordinary Portland cement

(OPC) and lower CO₂ emissions.

Workability. It refers to how easily a material, particularly concrete, can be

mixed, placed, and compacted without segregation or excessive effort. This property

is vital as it affects the handling, shaping, and finishing of construction materials,

ultimately influencing the efficiency and quality of the construction process.

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Chapter 2

REVIEW OF RELATED LITERATURE AND STUDIES

This chapter outlines the significant literature and research that the authors

took into account to reinforce the significance of the current study. It also offers a

synthesis of the art to enhance understanding of the research for improved

comprehension of the study.

1. Utilization of Agricultural Waste in Concrete

Concrete production, particularly cement manufacturing, is a major

contributor to global carbon emissions, accounting for approximately 7-8% of total

CO₂ emissions. The environmental impact stems from energy-intensive processes and

the chemical reaction of calcination, where limestone is heated to high temperatures,

releasing CO₂. That’s why researchers are exploring sustainable alternatives such as

fly ash, slag, and limestone, which can reduce emissions by up to 40% while

maintaining structural integrity. (Jessa, E., & Ajidahun, A. et al., 2024)

The study by (Kanmalai Williams et al., 2022) investigates the mechanical

properties of various concrete mixes made with environmentally sustainable

materials, such as fly ash, silica fume, plaster of Paris, and reclaimed rubber. They

served as partial replacements for cement and coarse aggregates and were utilized to
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combat growing environmental problems such as waste tire disposal and an

exhaustion of natural resources. In general, the last few years have demonstrated an

increasing trend for using industrial by-products and recycled materials in the

production of concrete due to natural aggregates depletion. In their result, the authors

revealed the improved compressive strength and durability of concrete and the most

robust values when 10% replacement levels are used were identified. Thus, the

authors conducted an extensive experimental program using M40 grade concrete and

implemented a Genetic Algorithm to simulate and optimize the replacement levels of

the four materials.

The mechanical properties of green concrete include compressive strength,

modulus of elasticity, and flexibility. The durability properties include water

absorption and porosity, acid and chloride resistance, and superior performance at

high temperatures. The study concludes that green concrete offers a sustainable,

environmentally friendly alternative to OPC concrete. (Hashmi, A. F., Khan, M. S.,

Bilal, M., Shariq, M., & Baqi, A. et al., 2022)

2. Application of Sustainable Material in Construction

The study by Ojerinde (2020) investigated the use of rice husk ash (RHA) as a

partial substitute for ordinary Portland cement (OPC) in compressed earth blocks

(CEBs) to develop affordable and sustainable housing in Nigeria. Various proportions

of RHA were tested to evaluate their mechanical and hygrothermal properties. Results

showed that CEBs with up to 30% RHA substitution met the strength requirements

for load-bearing walls, with 20% RHA providing the optimal balance between

structural performance and thermal comfort. Simulations confirmed that walls built

with 20% RHA-stabilized CEBs offered comparable indoor comfort to concrete walls
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while reducing cement use and environmental impact. The study concluded that RHA

is a viable and eco-friendly stabilizer for low-cost housing applications in tropical

climates. On the other hand, the study by Ejaz et al. (2022) reviews the use of coconut

shell (CS) waste as a lightweight aggregate in concrete. It finds that coconut shell

concrete (CSC) achieves sufficient compressive strength (2–36 MPa), reduced density

(1865–2300 kg/m³), and acceptable durability. CSC improves thermal insulation and

can be used in structural elements like beams, slabs, portal frames, and manhole

covers. The study concludes that CS is a sustainable and eco-friendly alternative to

conventional aggregates, especially suitable for construction in tropical regions.

3. Coconut Shell Ash (CSA) in Concrete

The study of (Bheel, N., Mangi, S. A., & Meghwar, S. L. et. al 2021)

conducted a detailed literature review of experimental research exploring the use of

coconut shell ash (CSA) as a partial replacement for OPC in concrete. The findings

indicated that using CSA, particularly at a 10% replacement level, improved

concrete’s mechanical properties due to its pozzolanic activity, although it reduced

workability because of its high water absorption. Chemical analysis confirmed CSA's

qualification as a Class N pozzolan, based on ASTM C618 standards, making it

suitable as a cementitious material. The review concluded that CSA is a viable and

eco-friendly material for enhancing concrete performance and reducing environmental

impact. An optimal 10% substitution level was consistently recommended to achieve

favorable strength and durability outcomes. However, higher CSA content can

negatively impact strength and increase vulnerability to sulfate attack, requiring

cautious application.(Adajar, M. A., Galupino, J., Frianeza, C., Aguilon, J. F., Sy, J.

B., & Tan, P. A. et al., 2020)

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4. Pozzolanic Activity of Coconut Shell Ash

Coconut shell ash (CSA) was tested as a partial cement replacement in

sustainable construction. Coconut shells were collected, cleaned, dried, crushed, and

calcined at over 700°C for three hours, then sieved through a 75 µm filter. CSA was

mixed with 42.5 N Dangote cement in increments of 0% to 25%, and normal sand

was used by BS EN 196-1. The Strength Activity Index (SAI) was calculated using

compressive strength tests at 7 and 28 days, as well as setting time tests on 0% and

15% CSA mixes. Chemical investigation using XRF revealed that CSA contains

80.64% SiO₂, 8.79% Al₂O₃, and 5.35% Fe₂O₃. It exceeds the ASTM C618-15 and

BS EN 197-1 Class N pozzolan standard of 70%. CSA met the specified standards for

Loss on Ignition (4.28%) and SO₃ (0.69%). At 28 days, the SAI reached 92%,

confirming its pozzolanic characteristics. Although setting times increased slightly

(e.g., 135 and 375 minutes for 15% CSA compared to 125 and 350 minutes in the

control group), it still performed well. Results show that CSA is technically possible

and environmentally sustainable. Up to 15% replacement reduces carbon emissions,

cement use, and agricultural waste without compromising structural integrity. (Joshua,

O., Olusola, K. O., Busari, A. A., Omuh, I. O., Ogunde, A. O., Amusan, L. M., &

Ezenduka, C. J. et al., 2018)

5. Rice Husk Ash (RHA) in Concrete

In the study by (Soni and Ojha et. al 2021), the methodology involved

replacing fine aggregate in M25 grade concrete with rice husk ash (RHA) at 0%, 5%,

10%, and 15% proportions. Standard 150mm concrete cubes were cast and tested for

compressive strength at 7, 14, and 28 days to evaluate the effects of RHA on concrete
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properties. The results indicated that 15% RHA replacement yielded the highest

compressive strength (27.1 N/mm² at 28 days), surpassing even the control mix (26.7

N/mm²). Conversely, 5% and 10% replacements showed a decline in strength

compared to the control. The discussion highlighted that RHA’s pozzolanic nature

improved impermeability and reduced concrete weight, supporting its potential as a

sustainable material. It concluded that RHA not only contributes to strength

development and environmental sustainability by recycling agricultural waste but also

optimizes concrete properties when used at appropriate dosages.

In the study by (Endale, Taffese, Vo, and Yehualaw et. al., 2023), the results

indicated that when processed correctly (via controlled combustion and grinding),

RHA exhibits high pozzolanic activity due to its amorphous silica content, which

enhances concrete strength and durability. The review showed that RHA improves

compressive, tensile, and flexural strengths up to an optimal replacement level

(typically between 10–20%), beyond which performance may decline. Additionally,

RHA significantly enhances durability by reducing water absorption, chloride ion

penetration, and permeability due to pore refinement and increased packing density.

Whichever, RHA is a viable supplementary cementitious material, promoting

sustainability by reducing cement consumption and managing agricultural waste,

thereby supporting a circular economy in construction.

6. Pozzolanic Activity of Rice Husk Ash

In the study by (Endale, Taffese, Vo, and Yehualaw et. al., 2023), RHA and

other supplemental cementitious materials must meet ASTM C618-19 chemical

composition criteria for pozzolan. Supplementary cementitious materials can have a

pozzolanic index of 70% or higher, per ASTM C618-19. RHA has a small amount of
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CaO and many oxides with above 70% silica. Incineration, processing, and grinding

increase RHA product ignition loss. Concrete is strengthened and durable when

thoroughly burned, and finely powdered rice husk ash is used. This material cannot be

widely used as pozzolan due to combustion sensitivity. RHA's cementitious efficiency

depends on the mixture's cement, rice husk ash, admixtures, water, and curing

conditions. Grinding parameters are important because RHA fineness affects

pozzolanic activity in addition to these considerations. Indeed, RHA grinding tactics

affect fineness, with mechanical grinding being more efficient than manual grinding.

Additionally, pozzolanic activity is affected by calcination temperature and

crystallinity.

The study of (Plando, F. R. P., Maquiling, J. T., et al., 2023) investigated the

strength and microstructural properties of self-compacting concrete (SCC)

incorporating rice husk ash (RHA) as a partial cement replacement. RHA was divided

into several particle sizes: unsieved, <300 µm, <125 µm, and <75 µm. Fifteen

concrete mixes were made with Ordinary Portland Cement, local aggregates, a

consistent superplasticizer dose, an air-entraining admixture, and 0%, 5%, 10%, and

15% rice husk ash (RHA) at water-to-binder ratios of 0.35, 0.40, and 0.45.

Compressive strength was measured at 7, 28, and 90 days, and SEM at 28 days.

Strength increased with finer rice husk ash (RHA) and lower water-to-binder (w/b)

ratios. The SC12 mix, with 15% RHA, particle size <75 µm, and w/b ratio <0.35,

showed the strongest strength and continuous improvements for 90 days. Less strong

were coarser or unsieved RHA mixes, such as SC01. High-performing combinations

exhibited a solid calcium silicate hydrate (CSH) gel, minimal unreacted particles, and

reduced microcracking, whereas weaker samples displayed honeycomb voids and

partial hydration. When combined with proper mixing techniques and low water-to-
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binder ratios, finely ground RHA at up to 15% replacement increases pozzolanic

activity, densifies the concrete matrix, and improves strength, making it an effective

supplementary cementitious material for self-consolidating concrete applications.

7. Red Clay (RC) as a Binder or Filler

The study of (Drissi, M., Horma, O., Mezrhab, A., & Karkri, M. et al., 2024)

explored using raw red clay as a partial replacement for cement in mortar. The

methodology included chemical and mineralogical characterizations of red clay using

X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron

microscopy (SEM), alongside sedimentation tests for particle size analysis. The X-ray

Fluorescence (XRF) analysis of the raw red clay revealed that it is predominantly

composed of silicon dioxide (SiO₂) at 50.43%, followed by aluminum oxide (Al₂O₃)

at 19.88%, and iron oxide (Fe₂O₃) at 15.96%. These three major oxides are critical

for pozzolanic activity and contribute to the potential of red clay as a supplementary

cementitious material. Additionally, the clay contains 5.87% potassium oxide (K₂O),

2.30% calcium oxide (CaO), and 1.96% titanium dioxide (TiO₂). Minor components

include phosphorus pentoxide (P₂O₅) at 1.00%, strontium oxide (SrO) at 0.21%,

zirconium dioxide (ZrO₂) at 0.10%, and vanadium pentoxide (V₂O₅) at 0.08%. The

high content of silica and alumina, along with the presence of iron and other oxides,

supports the suitability of red clay for use in cement blends, offering both reactivity

and potential performance benefits in construction applications.Various mix designs

were tested by substituting 0–30% of cement with clay. Findings indicated that a clay

replacement of up to 5% preserved strength while enhancing thermal insulation and

reducing costs by 27% and CO₂ emissions by 30%. Increased clay content (beyond

5%) further improved insulation and ecological benefits but significantly

compromised strength. The study concluded that small quantities of red clay can be
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utilized in structural applications, while higher quantities are more suitable for non-

structural parts (like walls or insulating purposes) supporting sustainable and cost-

effective construction practices. On the other hand, the study by Islam et al., (2024)

developed lightweight structural concrete by using manufactured lightweight

aggregates made from leftover glass, rice husk ash, and red clay to partially replace

natural coarse aggregate. Drying, grinding, granulation, and high-temperature

sintering were the methods used to process the materials. According to tests, it

showed that replacing up to 30% of natural aggregate with lightweight aggregate

(especially red clay-based) produced concrete with good compressive strength (up to

48 MPa), lower density, better thermal insulation, and reduced chloride permeability.

The study of (Mohamed, H. A. et al., 2017) examined the performance of

concrete modified with red clay waste from brick production, when exposed to fire.

324 concrete specimens were prepared and tested, with two mix types. Type I (cement

replaced with red clay) and Type II (sand replaced with red clay). After being cured

for 28 days, specimens were exposed to fire for 30-60 minutes, and tested for

compressive, tensile, and flexural strength. Slump tests were conducted to assess

workability, and scanning electron microscopy (SEM) was used to evaluate

microstructural changes. The study found that the optimal red clay replacement level

for cement and sand is 15%. This increases compressive strength by 16.8% and

tensile strength by 52.8% after 30 minutes of fire exposure. SEM images confirmed

the formation of calcium silicate hydrates in homra-modified mixes. Longer fire

exposure reduced mechanical properties. As a result, this could be effectively used as

a partial replacement for both cement and sand in concrete to enhance fire resistance

and mechanical properties. The ideal replacement levels were 15% for cement and

25% for sand. Adding that, the study of (Lu, X., Yu, Q., Xu, J., Yue, B., & Sheng, M.
 17

et al., 2023) aimed to enhance red clay's strength by using industrial solid waste

materials as stabilizers. Red clay samples from Nanchang, China, were modified

using steel slag, fly ash, and GGBS powders. The experiment involved comparing the

effects of these materials to ordinary Portland cement. Characterization techniques

included Atterberg limits, compaction testing, SEM, and XRF. The study found that

adding all four additives significantly improved red clay strength, with OPC showing

the most significant improvement. SS showed the best performance, with a 252%

increase after 21 days. FA and GGBS showed modest improvements, with peak UCS

increases of 131% and 140%, respectively. The failure modes varied, with OPC-

modified clay showing shear failure. In conclusion, OPC provided the best

enhancement in red clay strength, followed by SS, GGBS, and FA. While all additives

improved performance to varying degrees, industrial solid waste powders, especially

SS, offer promising alternatives to cement for sustainable and cost-effective soil

stabilization.

8. Utilization of Rice Husk Ash and Coconut Shell Ash

The study by (Mokhtar et al. 2022) analysed the performance of RHA and

CSA as partial substitutions in concrete. Based on earlier research results, the authors

evaluated the influence of the materials on compressive strength, density, and

workability of concrete. It was evident from the results that the workability was

increased, and the compressive strength was retained better with RHA than CSA and

is more suitable to be used in concrete, particularly for M30 and M35 grades. For both

materials, density and compressive strength were decreased at high replacement

levels, so a low replacement rate (less than 10 %) of waste material is suggested.

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Generally, RHA is suitable for the development of green, lightweight concrete at low

load.

9. Combine Effect of Rice Husk Ash and Fly Ash

In the study of (Sathawane, S. H., Vairagade, V. S., & Kene, K. S. 2013),

using 43-grade Ordinary Portland Cement, this study used Rice Husk Ash (RHA) and

Fly Ash (FA) from industrial facilities in Maharashtra, India, as partial cement

substitutes in concrete. From 30% fly ash and 0% rice husk ash to 15% of each, using

superplasticizers to ensure workability, 30% cement substitution was investigated. All

concrete mixtures were tested for slump, compressive strength (7–90 days), tensile,

and flexural strength (28 days). The best composition was 22.5% FA and 7.5% RHA,

yielding a 28-day compressive strength of 41.78 MPa, which is 30.15% higher than

the target strength and slightly lower than that of the control mix. Flexural strength

rose to 7.55 MPa, whereas split tensile strength fell to 3.96 MPa. FA improved

workability, while RHA decreased it due to its high water absorption. FA and RHA

integration improves compressive and flexural strength, encouraging sustainable

construction. RHA reduces workability; however, superplasticizers help. The study

found that 22.5% FA and 7.5% RHA produce strong, ecologically friendly, and cost-

effective concrete from industrial and agricultural waste.

10. Environmental Impacts of Cement Production

The cement industry is a significant contributor to environmental degradation,

accounting for approximately 5-7% of global CO₂ emissions (Hendricks et al., 1998;

Humphreys & Mahasenan, 2002). These emissions primarily result from the
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calcination of limestone and fuel combustion during clinker production. In addition to

carbon dioxide, cement manufacturing releases nitrogen oxides (NOx), sulfur dioxide

(SO₂), volatile organic compounds (VOCs), and particulate matter, all of which

contribute to air pollution and pose serious health risks (Karstensen, 2006 & 2007).

To mitigate these environmental impacts, researchers and industry leaders are

exploring alternative materials, such as rice husk ash, coconut shell ash, and fly ash,

to reduce reliance on traditional cement components Gartner et al., (2004)

11. Factors Affecting Strength of Green Concrete

There are multiple factors leading to green concrete’s strength. Mixture

proportions such as the use of supplementary cementitious materials (SCMs) such as

fly ash, rice husk and silica fume are increasingly common in order to achieve long

term durability while reducing the early strength development (Almasailam et al.,

2025). Water is also a factor that directly influences strength—when more water is

added, normal compressive strength increases, but workability suffers, sometimes

necessitating super plasticizing agents (Civil Engineer Mag, 2025). Packing density

is influenced by the nature of the aggregate, such as the gradation and shape, and

concrete strength increases owing to well-graded aggregate. There are conditions of

curing, such as carbonation curing, which may lead to an accelerating CO₂ uptake,

increasing the early-age strength and decreasing emission (Gopal & Sain, 2024).

Through optimal mix design and curing methods, scientists are proving the potential

of green concrete for eco-friendly construction.

12. Supplementary Cementitious Materials (SMS’s)

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Fantilli and (Jóźwiak-Niedźwiedzka et al., 2021) explored the use of

supplementary cementitious materials (SCMs) in concrete, highlighting their impact

on durability, mechanical properties, and sustainability. The research involved

chemical and physical analyses to assess SCMs before and after hydration, with tests

measuring compressive strength, permeability, and resistance to aggressive

environments. Findings indicate that SCMs enhance concrete performance by

reducing porosity, improving flexural strength, and increasing resistance to

carbonation, chloride penetration, and sulfate exposure. Alternative materials, such as

biomass wood ash and recycled cement mortar, showed promise as SCM

replacements. The study concluded that SCMs provide viable solutions for sustainable

construction, reducing environmental impact while maintaining structural integrity.

On the other hand, the study of (Toutanji, H., Delatte, N., Aggoun, S., Duval, R., &

Danson, A. 2003) tested 14-day-cured concrete compressive strength and durability

with silica fume, fly ash, slag, and their mixtures. The 16 concrete mix designs

included a control mix, additive blends, and six cement, silica fume, slag, and fly ash

combinations. For workability, cementitious materials, sand, gravel, and water were

mixed with superplasticizers. Mix A (10% SF, 25% slag, 15% FA) increased strength

by 22%, while Mix B (5% SF, 35% slag, 10% FA) decreased strength by 15%.

Combination A and control were the most freeze-thaw stable, meanwhile wet–dry

testing showed that 30% fly ash and 80% slag increased strength by 30% and 25%,

respectively, after prolonged curing. In both durability tests, Mix A outperformed

single-additive blends. Cured fly ash and slag perform best. This study indicated that

8% silica fume boosted short-term compressive strength most, but higher doses

decreased it—strongest slag at 70% replacement. Thus, Mix A (10% SF, 25% slag,

15% FA) strengthened and lasted. Control and silica fume mixes performed best in
 21

freeze-thaw testing, while wet–dry cycling improved fly ash and slag concretes. Fly

ash and slag benefit from longer cure times, but combined combinations can produce

durable, high-performance concrete.

Chapter 3

METHODOLOGY

This chapter presents a comprehensive framework for the research study,

outlining the systematic approach taken in the gathering, processing, and

interpretation of data. The methodology section includes an in-depth explanation of

the preparation of materials, the proportioning of the concrete mix, and the testing

techniques employed to assess the workability and compressive strength of the

concrete mixture that incorporates coconut shell ash, rice husk ash and red clay as

partial cement replacement. This systematic approach guarantees the collection of

robust and dependable data, enabling a complete understanding of how the partial

cement replacement influences the performance attributes of the concrete.

3.1 Research Design

This study employs an experimental research design, which is appropriate for

analyzing the effects of partial cement replacements (CSA, RHA, and RC) on the

compressive strength of concrete. The independent variables are the varying

proportions of CSA, RHA, and RC, while the dependent variable is the compressive

strength of concrete at different curing periods (7, 14, and 28 days). The study
 22

includes a control group (0% replacement) and two experimental groups with

different blend ratios.

Control Group 1: 0% CSA, 0% RHA, and 0% RC

Group 2: 10% CSA, 25% RHA, and 5% RC

Group 3: 10% CSA, 20% RHA and 5% RC

Group 4: 5% CSA, 15% RHA, 5% RC

Table 3.1

Mix Design Coconut Shell Ash Rice Husk Ash Red Clay

Conventional 0% 0% 0%

Mix A 10% 25% 5%

Mix B 10% 20% 5%

Mix C 5% 15% 5%

Composition Of Mixtures in Percentage (%).

3.2 The objective of this research was to evaluate how effective coconut shell ash, rice

husk ash, and red clay are in enhancing the sustainability, workability, and

durability of concrete mixtures. A structured experimental approach was utilized

to gather empirical data, placing emphasis on assessing the compressive strength

and workability of the concrete mixes. Comprehensive testing and analysis were

conducted to investigate the combined effects of coconut shell ash, rice husk ash,

and red clay on the properties of concrete.

3.2 Research Locale

 23

The research will take place at La Salle University in Ozamis City. The

conventional materials required for the study, including coarse aggregates, fine

aggregates, and ordinary Portland cement, will be sourced from local hardware stores

in Ozamis City. The collection of rice husk ash (RHA) will occur in Maranding, Lala,

Lanao Del Norte while coconut shell ash (CSA) will occur in Purok-4 Tonggo,

Tudela, Misamis Occidental and red clay will be acquire at Lama-lama, Lanao Del

Norte.

3.3 Research Instrument

The following tools and instruments were utilized for the collection and

analysis of data:

Materials and Instrument Description

Coconut Shell Ash

Coconut shell ash (CSA) is a sustainable

material used to partially replace cement,
improving concrete strength and reducing
environmental impact.

Rice Husk Ash

Rice husk ash (RHA) is a silica-rich pozzolan

 24

from burned rice husks, used as a partial cement

replacement to enhance concrete strength and
sustainability.

Red Clay

Red clay is a natural material rich in alumina

and silica, used as a partial replacement for
cement to reduce costs and environmental impact
while maintaining concrete performance.

Cement

Cement is a binding material that hardens when

mixed with water, commonly used in construction
to make concrete and mortar.

Coarse Aggregates

Coarse aggregates are large particles, such as

gravel or crushed stone, used in concrete to
provide strength, bulk, and stability.
 25

Fine Aggregates

Fine aggregates are small particles like sand

used in concrete to fill gaps between coarse
aggregates and improve workability and finish.

Barrel

A barrel is a metal container used for controlled

burning of materials like coconut shells, rice
husks, and red clay to produce ash for cement
replacement.

Weighing Scale

For accurately measuring the raw materials.

Shovel

A shovel is a hand tool used for collecting,

mixing, and transferring materials like coconut
shell ash, rice husk ash, and red clay during
 26

preparation.

Slump Test Cone

Meter Stick

A meter stick is utilized alongside the slump test

cone to precisely measure the slump of fresh
concrete.

Trowel

The trowel helps in filling and leveling the slump

test cone during the assessment of fresh concrete
workability.

Concrete Molds

For casting test specimens.

 27

Curing Tank

To maintain specimens in water for designated

curing periods.

Universal Testing Machine

(UTM)

For measuring the compressive strength of

concrete specimens.

Sieve (200 mm)

For particle size analysis of the raw materials.

Oven

For drying CSA, RHA, and RC.

Grinder
 28

For pulverizing CSA, RHA, and RC.

3.4 Research Flow

Figure 2 presents a timeline of the activities to be conducted in the study. It

outlines the critical steps and procedures that will guide the researchers. The use of

research flow diagrams will assist the researchers in ensuring systematic and

comprehensive execution of the study.

1. Material Acquisition

a) Collect the necessary materials: rice husk, coconut shell, red clay,

conventional aggregates, and ordinary Portland cement.

2. Preparation of Rice Husk Ash (RHA) and Coconut Shell Ash (CSA)
 29

a) Clean and sun-dry the gathered rice husk and coconut shell to

eliminate impurities.

b) Burned in a furnace, cooled, and ground or milled the rice husk and

coconut shell in a controlled setting to generate ash, ensuring

optimal temperature and conditions.

c) Sift the resulting rice husk ash and coconut shell ash to obtain fine

particles suitable for incorporation into the concrete mixture.

3. Physical Analysis of Rice Husk Ash (RHA) and Coconut Shell Ash (CSA)

a.) Submitted the rice husk ash and coconut shell ash samples to a

laboratory for testing.

b.) Conducted physical analyses to ascertain the properties of the rice

husk ash and coconut shell ash, including particle size, specific surface

area, and pozzolanic activity.

4. Preparation of Red Clay

a) Ensured that the red clay is collected, dried, ground, sieved, mixed

and homogenized.

b) Stored for testing and formulation.

5. Proportioning of Concrete Formulations

a) Prepare materials for three distinct mixtures:

i. Control mixture (0% CSA, 0% RHA and 0% RC).

ii. Mixture with 10% CSA, 25% RHA and 5% RC.

iii. Mixture with 10% CSA, 20% RHA and 5% RC.

iv. Mixture with 5% CSA, 15% RHA and 5% RC.

6. Concrete Mixing
 30

a) Combine the materials for each batch in accordance with standard

concrete mixing protocols.

b) Ensure uniformity and consistency across all mixtures.

7. Molding and Demolding

a) Pour the blended concrete into molds for specimen preparation.

b) Allow the concrete to be cured for the necessary duration before

demolding.

8. Curing of Concrete Specimens

a) Cure the demolded specimens in water for 7, 14, and 28 days to

guarantee adequate hydration and strength development.

9. Compressive Strength Evaluation

a) Transport the cured concrete specimens to the laboratory for

testing.

b) Conduct compressive strength evaluations for each curing duration

(7, 14, and 28 days).

c) Document and analyze the findings to evaluate the performance of

the various concrete mixtures.

10. Analysis and Interpretation of Data:

a) Assess the compressive strength and workability of the three

concrete mixtures and examine the effects of rice husk ash, coconut

shell ash and red clay on the sustainability, workability, and

durability of the concrete.

3.6 Data Gathering and Research Procedure

 31

A number of processes and procedures were put in place to make the

data collection process easier. These consist of the following:

(1) Collection of rice husk and coconut shell

(2) Gathering of red clay

(3) Concrete Mix Designs and curing

(4) Compressive Testing; and

(5) Gathering of data.

1. Collection of Rice Husk and Coconut Shell and Production of Rice Husk

Ash and Coconut Shell Ash

In this study, the process of producing rice husk ash (RHA) and coconut shell

ash (CSA) involved gathering rice husks and coconut shells from local agricultural

sources in Lanao Del Norte and Misamis Occidental, respectively. The rice husks

were collected from nearby mills, while coconut shells were obtained from

households and local markets, where they are often discarded after the meat is

extracted.

Both materials were thoroughly cleaned to eliminate soil, residues, or any

unwanted organic substances. After being cleaned and sun-dried, the rice husks and

coconut shells were burned separately in metal barrels using an open burning

technique. The combustion was carried out in a controlled environment with limited

oxygen to encourage partial carbonization and ensure the formation of proper ash.

Each burning session lasted approximately around three hours.

Following the combustion process, the remaining ashes, which varied in color

from light gray to dark gray, were allowed to cool naturally within the barrels to

prevent thermal shock and maintain their pozzolanic characteristics. After they were
 32

fully cooled, the ashes were meticulously gathered and sifted to remove larger debris

and any unburned materials. The resulting fine ash was subsequently kept in airtight,

moisture-resistant containers to ensure its chemical stability for future use in the

concrete mixture.

2. Gathering of Red Clay

The red clay used in this research was carefully collected from naturally

occurring deposits in selected rural areas of Lanao Del Norte. Upon collection, the

clay was first air-dried to reduce its moisture content and facilitate easier handling.

Once adequately dried, the red clay was ground into finer particles using a mechanical

grinder to enhance its reactivity when used as a supplementary cementitious material.

After grinding, the material was sieved to remove coarse particles and ensure

uniformity in texture. The sieved red clay was then thoroughly mixed and

homogenized to achieve a consistent composition throughout the batch. Finally, the

prepared red clay was stored in clean, airtight, and moisture-resistant containers,

keeping it stable and ready for use in subsequent testing and concrete formulation.

3. Concrete Mix Design and Curing

The concrete mix designs used in this study were classified into three

groups to evaluate both the separate and combined impacts of rice husk ash,

coconut shell ash and red clay on the performance of concrete. Each mix

adhered to a uniform ratio for aggregates, cement, and water to ensure

 33

consistency, with only the partial cement replacement differing among the

batches.

Mix A (Conventional Mix): This mix served as the control group and

contained 0% rice husk ash, 0% coconut shell and 0% red clay. It represented

standard concrete composition without any sustainable replacement, providing

a baseline for comparison in compressive strength and durability performance.

Mix B: In this formulation, coconut shell ash was (10%), rice husk ash was

(25%) and 5% of red clay. This mix was designed to evaluate the influence of

waste materials as partial replacement of cement on workability and

mechanical properties.

Mix C: In this formulation, it can be seen a mixture lower than Mix 2 which is

coconut shell ash was (10%), rice husk ash was (20%) and 5% of red clay.

This mixture was created to assess how waste materials with higher

percentages can serve as a partial substitute for cement, affecting workability

and mechanical characteristics.

Mix D: In this formulation, it can be seen a mixture lower than Mix 3 which is

coconut shell ash was (5%), rice husk ash was (15%) and 5% of red clay. This

blend was developed to evaluate the potential of using waste materials with

greater percentages as a partial replacement for cement, influencing both

workability and mechanical properties.

4. Compressive Strength Testing

The compressive strength tests on the concrete samples were performed to

evaluate the mechanical properties of each mix design at defined curing periods.
 34

Following 7, 14, and 28 days of curing, the concrete cylinders were taken out of the

curing tank and carefully dried to remove surface moisture that could affect test

precision.

For every blend and corresponding curing duration, four cylindrical samples

were examined to guarantee the reliability and consistency of the outcomes. Before

conducting the tests, all samples underwent a visual inspection for any cracks, defects,

or irregularities that might affect their structural integrity. The compressive strength

assessment was performed using a Universal Testing Machine (UTM), which applied

a gradually increasing axial force until the sample failed.

Each cylinder was centered on the lower platen of the universal testing

machine, with the top platen meticulously aligned to guarantee consistent load

distribution. The machine applied force at a regulated pace, following standard testing

protocols. After each specimen failed, the peak load was noted, and the compressive

strength was determined by dividing the failure load by the specimen's cross-sectional

area.

The average compressive strength for each group of four specimens at each

curing period was calculated, establishing a dependable foundation for evaluating the

structural capabilities of the various concrete mixtures. This thorough testing

procedure allowed the researchers to evaluate the impact of coconut shell ash, rice

husk ash and red clay on enhancing the compressive strength of concrete.

5. Gathering of Data

Each set of concrete specimens' compressive strength findings were

systematically recorded, analyzed, and interpreted as part of the data collection and
 35

processing process for this study. The highest load at failure for each specimen was

meticulously recorded in kilonewtons (kN) using the display output from the

Universal Testing Machine following the completion of the compressive strength tests

on five specimens for each concrete mix at 7, 14, and 28 days.

The recorded load was then divided by the cylindrical specimen's cross-

sectional area to translate these results to compressive strength in megapascals (MPa).

To guarantee precision and uniformity, the compressive strengths of the four

specimens for every mix and curing time were then compiled and averaged. A

representative figure of each mix's performance was given by the mean values.

After calculating the average compressive strengths, the data was compiled

and arranged for better comparison among the four distinct concrete mix designs: the

traditional mix, Mix B, Mix C, and Mix D. The outcomes were subsequently

illustrated through bar charts to visually represent the trends and variations in

performance across different curing periods and mix types.

In order to evaluate the effectiveness of coconut shell ash, rice husk ash and

red clay as partial replacement of cement, the researchers compared the average

strengths of the modified mixes to those of the control mix. Changes in compressive

strength were documented and assessed through percentage differences. This

approach to data analysis enabled the researchers to make conclusions about the

influence of each mix on both early and long-term strength, thereby supporting the

study's aim of encouraging sustainable and high-performance concrete production.

Sampling and Preparation

Step 1: Selection of Concrete Mix Designs

 36

● The research utilized four distinct concrete mix designs:

o Mix A (Control): 0% CSA, 0% RHA and 0% RC

o Mix B: 10% CSA, 25% RHA and 5% RC.

o Mix C: 10% CSA, 20% RHA and 5% RC.

o Mix D: 5% CSA, 15% RHA and 5% RC.

These mix designs were selected to evaluate the combined effects of CSA, RHA

and RC on the compressive strength and performance of concrete.

Step 2: Measurement of Raw Materials

● The components for every mixture were measured carefully with a digital

scale to guarantee accurate ratios.

o Cement: Ordinary Portland cement (OPC).

o Fine aggregates: Sand passing through a 4.75 mm sieve.

o Coarse aggregates: Crushed stone or gravel of appropriate size.

o Coconut Shell Ash (CSA): Added at 10% and 5% by weight of

cement in Mixes B, C and D.

o Rice Husk Ash (RHA): Added at 25%, 20% and 15% by weight of

cement in Mixes B, C and D.

o Red Clay (RC): Incorporated at 5% by weight of cement in Mixes

B, C and D.

o Water: Clean and potable water measured to maintain the desired

water-cement ratio.
 37

Step 3: Mixing Procedure

o The dry ingredients (cement, fine aggregates, coarse aggregates, RHA,

CSA and RC) were thoroughly blended in a mechanical concrete mixer to

ensure uniform distribution of particles.

o Water was subsequently incorporated into the dry mixture, and the

ingredients were blended for another 5 minutes until a uniform consistency

was obtained. The duration and method of mixing were meticulously

managed to avoid overmixing and segregation.

Step 4: Preparation of Molds

o The molds utilized were conventional cylindrical concrete molds

measuring 150 mm in diameter and 300 mm in height, which were cleaned

and treated with form oil to avoid adherence of the concrete during the

demolding process.

o Each mold received a distinct identification label to facilitate accurate

monitoring of the corresponding mix design and curing duration.

Step 5: Pouring Concrete into Molds

o The freshly mixed concrete was poured into the molds in three equal layers

to guarantee consistency.

o Every layer was compacted using a standard tamping rod (16 mm in

diameter and 300 mm long), with 25 tamping actions performed to

eliminate trapped air and guarantee adequate consolidation.

o After compaction, a trowel was used to level the surface of the concrete for

a smooth finish.
 38

Step 6: Initial Setting Period

o Once the molds were filled, the concrete was allowed to remain

undisturbed for 24 hours at room temperature (around 23 ± 2°C) to

facilitate initial setting and hardening.

o The molds were kept in a controlled environment with stable temperature

and humidity conditions during this period.

Step 7: Demolding

o After the initial 24-hour curing period, the specimens were meticulously

demolded. The concrete cylinders were gently taken out of the molds to

avoid any damage to the surface or distortion.

o The specimens were labeled according to their mix design and curing

duration.

Step 8: Curing of Specimens

o The concrete specimens were placed in a curing tank filled with clean

water at a temperature of 23 ± 2°C to simulate standard curing conditions.

o The samples were completely submerged in water for specified curing

durations of 7, 14, and 28 days, enabling them to maintain hydration and

develop compressive strength.

o The curing tank was regularly checked to ensure the water temperature and

cleanliness were upheld during the entire curing period.

Step 9: Sample Quantity

 39

o For each mix design and curing period, four specimens were prepared.

This resulted in a total of:

o 4 mix designs × 3 curing intervals × 4 specimens per mix = 48

concrete specimens in total.

This approach guarantees statistical reliability and minimizes variation in the

outcomes. This methodical sampling technique ensures uniformity and accuracy

in specimen preparation, allowing for precise evaluation of the impact of bamboo

charcoal ash and sugarcane molasses on the compressive strength and

performance of concrete.

A. Sieving of Fine Aggregates (Sand)

1. Sample Collection

o Using a shovel, a representative sample of fine aggregates (sand) was

taken from the stockpile.

o Used the quartering method to obtain approximately 500–1000 grams

for testing.

2. Drying the Sample

o Sample was oven-dried in an oven at a temperature of 110 ± 5°C for a

duration of 24 hours to remove moisture content.

o Cooled the dried sample to room temperature before sieving.

3. Weighing the Sample

 40

o Weighed the dried sample using a calibrated weighing scale to obtain

the initial mass (W₀).

4. Setup of Sieve Stack

o Set up a sequence of standard sieves in order of decreasing mesh size

(e.g., 4.75 mm, 2.36 mm, 1.18 mm, 600 μm, 300 μm, 150 μm, and pan)

on a mechanical sieve shaker.

o Ensured the sieve stack is clean and dry.

5. Sieving Operation

o Put the fine aggregate sample on the uppermost sieve.

o Operated the sieve shaker for 10 to 15 minutes to guarantee effective

separation according to particle size.

6. Weighing Retained Fractions

o After sieving, individually measure the weight of the material collected

on each sieve.

o Recorded the mass of each fraction for gradation analysis.

7. Gradation Analysis

o Determine the percentage retained and percentage passing for every

sieve size.

o Evaluated the outcomes against standard specifications (such as ASTM

C33) to assess appropriateness.

 41

8. Storage for Use

o Stored the sieved fine aggregates in a clean, dry container labeled

appropriately for later use in mixing.

B. Sieving of Coarse Aggregates (Gravel)

1. Sample Collection

o Gathered a typical coarse aggregate sample utilizing suitable sampling

equipment.

o Employed the quartering technique to acquire a 2–5 kg sample for the

sieving process.

2. Drying the Sample

o Oven-dried the gravel at 110 ± 5°C for at least 24 hours to remove

moisture.

o The sample was then permitted to cool to room temperature prior to

testing.

3. Weighing the Sample

o Weighed the total dry sample accurately using a weighing scale and

record the initial mass (W₀).

4. Setup of Sieve Stack

 42

o Set up sieves with standard dimensions suitable for coarse aggregate

grading (e.g., 25 mm, 20 mm, 12.5 mm, 10 mm, 4.75 mm, and pan).

o Arrange them in descending order and position them on a mechanical

shaker.

5. Sieving Operation

o Place the sample onto the upper sieve and run the mechanical shaker

for 10 to 15 minutes.

6. Weighing Retained Fractions

o Carefully remove each sieve and weigh the aggregate retained.

o Recorded the mass retained on each sieve.

7. Gradation Analysis

o Determine the cumulative percentage retained and the percentage

passing.

o Compared with standard gradation requirements to validate the

suitability of a concrete mix.

8. Storage for Use

o Stored the sieved coarse aggregates in a moisture-free container

labeled with size classification.

Determination of Moisture Content in Fine Aggregates (Sand)

 43

1. Sample Collection

o Gathered a representative sample of fine aggregates from the storage

pile using a shovel.

o Used the quartering method to obtain approximately 500 grams of

sample.

2. Initial Weighing (Wet Weight)

o Weighed the moist sample using a digital weighing scale.

o Recorded the wet mass (W₁) to the nearest 0.1 gram.

3. Drying Process

o Put the sample into a metal container and distribute it uniformly.

o Heat the sample in a laboratory oven at 110 ± 5°C for 24 hours, or until

a stable weight is achieved.

4. Cooling

o Let the dried sample cool in a desiccator or at room temperature to

avoid moisture absorption.

5. Final Weighing (Dry Weight)

o Weigh the dried sample and record the dry mass (W₂).

o This produced the moisture level expressed as a percentage of the dry

weight..

B. Determination of Moisture Content in Coarse Aggregates (Gravel)

1. Sample Collection
 44

o Gather a representative sample of coarse aggregate weighing

approximately 2–3 kg, from various locations within the storage pile.

2. Initial Weighing (Wet Weight)

o Weighed the entire moist sample on a digital scale.

o Record the wet mass (W₁).

3. Drying Process

o Spread the aggregate uniformly in a metal container.

o Placed in a laboratory oven at a temperature of 110 ± 5°C for a

minimum of 24 hours, or until a stable mass is reached.

4. Cooling

o Cooled the dried aggregate in a desiccator to prevent moisture

reabsorption.

5. Final Weighing (Dry Weight)

o Weigh the dry sample and record the dry mass (W₂).

6. Moisture Content Calculation

o Applied the same formula:

Sieving of Coarse and Fine Aggregates

A. Sieving of Fine Aggregates (Sand)

1. Sample Collection
 45

o Using a shovel, a representative sample of fine aggregates (sand) was

taken from the stockpile.

o Used the quartering method to obtain approximately 500–1000 grams

for testing.

2. Drying the Sample

o Oven-dried the sample at a temperature of 110 ± 5°C for 24 hours to

eliminate moisture content.

o Cooled the dried sample to room temperature before sieving.

3. Weighing the Sample

o Weighed the dried sample using a calibrated weighing scale to obtain

the initial mass (W₀).

4. Setup of Sieve Stack

o Set up a sequence of standard sieves in order of decreasing mesh size

(e.g., 4.75 mm, 2.36 mm, 1.18 mm, 600 μm, 300 μm, 150 μm, and pan)

on a mechanical sieve shaker.

o Ensured the sieve stack is clean and dry.

5. Sieving Operation

o Placed the fine aggregate sample on the top sieve.

 46

o Operate the sieve shaker for 10–15 minutes to ensure adequate

separation based on particle size.

6. Weighing Retained Fractions

o After sieving, the weight of the material held on each sieve was

recorded separately.

o Recorded the mass of each fraction for gradation analysis.

7. Gradation Analysis

o Calculated the percentage retained and percentage passing for each

sieve size.

o Analyzed results with established standards (such as ASTM C33) to

assess compatibility.

8. Storage for Use

o Stored the sieved fine aggregates in a clean, dry container labeled

appropriately for later use in mixing.

B. Sieving of Coarse Aggregates (Gravel)

1. Sample Collection
o Gather a representative coarse aggregate sample using appropriate

sampling tools.

o Used the quartering method to obtain a 2–5 kg sample for sieving.

2. Drying the Sample

 47

o Oven-dried the gravel at 110 ± 5°C for at least 24 hours to remove

moisture.

o Allowed the sample to cool to room temperature before testing.

3. Weighing the Sample

o Weighed the total dry sample accurately using a weighing scale and

record the initial mass (W₀).

4. Setup of Sieve Stack

o Set up the sieves with standard sizes appropriate for coarse aggregate

grading (e.g., 25 mm, 20 mm, 12.5 mm, 10 mm, 4.75 mm, and pan).

o Arrange them in descending size order and position them on a

mechanical shaker.

5. Sieving Operation

o Place the sample into the upper sieve and operate the mechanical

shaker for 10–15 minutes.

6. Weighing Retained Fractions

o Gently remove each sieve and weigh the aggregate retained.

o Recorded the mass retained on each sieve.

7. Gradation Analysis

o Compute the cumulative percent retained and percent passing.

o Compared with standard gradation requirements to confirm

acceptability for concrete mix.

 48

8. Storage for Use

o Stored the sieved coarse aggregates in a clean, dry container labeled

appropriately for later use in mixing.

Furthermore, the subsequent phase in the mix design calculation involved

establishing the volume of coarse aggregates for each unit volume. The

nominal maximum size of coarse aggregates and the fineness modulus of fine

aggregates are key attributes needed to advance in this stage. By referring to

table 3.4, the volume of coarse aggregates per unit volume was determined.

Nominal Volume of dry-rodded coarse aggregates per unit volume of

Max size of concrete for different fineness of fine aggregates
Aggregates 2.4 2.6 2.8 3.0
(mm)
9.5 0.5 0.48 0.46 0.44
12.5 0.59 0.57 0.55 0.53
19 0.66 0.64 0.62 0.60
25 0.71 0.69 0.67 0.65
37.5 0.75 0.73 0.71 0.69
50 0.78 0.76 0.74 0.72
75 0.82 0.80 0.78 0.76
100 0.87 0.85 0.83 0.81
Table 3.3 Volume of coarse aggregate per unit volume of concrete

Cleaning and Burning of Coconut Shell to Produce Coconut Shell Ash (CSA):

1. Sourcing of Coconut Shell

o Gather waste coconut shells from agricultural sources where they are

considered by-products.

2. Cleaning
 49

o Eliminate any leftover coconut flesh, husk, or other debris to ensure

that only clean shells are utilized for combustion.

3. Drying

o Allow the coconut shells to air-dry for 24-48 hours to ensure they are

dry, brittle, and lightweight before burning to remove moisture and

provide better combustion efficiency.

4. Crushing or Breaking

o Crush the coconut shells into smaller pieces that help promote even

and complete combustion.

5. Preparation of the Combustion Site

o Prepared a metal barrel with ventilation holes to allow airflow.

o Set up the site in a safe, open area for controlled burning.

6. Stacking the Coconut Shell in the Barrel

o Place dried coconut shells in the barrel along with small twigs or

shavings to use as kindling.

7. Ignition and Controlled Burning

o Used a blowtorch to ignite the coconut shells from the bottom.

o Maintained controlled burning for approximately 3 hours at 500°C–

550°C.

8. Sealing and Cooling

 50

o Once burning is complete, seal the barrel loosely using a metal lid to

limit oxygen and allow pyrolysis.

o Let it cool naturally for 12–24 hours.

9. Collection of Ash

o Open the barrel and collect the charred coconut shell.

10. Pulverization

o Crush the coconut shell ash manually or with a grinder into fine

powder.

11. Sieving

o Passed the powder through a #200 sieve to ensure uniform particle

size.

12. Storage

o Placed the completed coconut shell ash into sealed, moisture-resistant

bags and stored them in a cool, dry environment.

Cleaning and Burning of Rice Husk to Produce Rice Husk Ash (RHA):

1. Sourcing of Rice Husk

o Obtain rice husks from rice mills after the dehusking process.

2. Cleaning the Rice Husk

o Ensure the husk is clean and free from impurities such as stones, soil,

and other plant materials.

3. Drying
 51

o Air-dry the husk under the sun for 24-72 hours to reduce moisture.

4. Preparation for Combustion Site

o Prepared a metal barrel with ventilation holes to allow airflow.

o Set up the site in a safe, open area for controlled burning.

5. Loading the Coconut Shell in the Barrel

o Load the dried rice husk gradually in the barrel along with small twigs

or paper to use as kindling.

6. Sealing and Cooling

o Once burning is complete, seal the barrel loosely to limit oxygen and

allow pyrolysis.

o Let it cool naturally for 12–24 hours.

7. Collection of Ash

o Open the barrel and collect the charred rice husk.

8. Pulverization

o Crush the rice husk manually or with a grinder into fine powder.

9. Sieving

o Passed the powder through a #200 sieve to ensure uniform particle

size.

10. Storage
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o Stored the final rice husk ash in airtight, moisture-proof containers,

dry place.

Controlled Burning of Coconut Shell Ash and Rice Husk Ash Production

1. Preparation of Coconut Shell and Rice Husk Material

o Ensured coconut shell and rice husk were adequately dried and free

from any surface dirt or organic debris to minimize smoke and enhance

combustion performance.

2. Selection and Setup of the Combustion Vessel

o Used a metal barrel equipped with air openings for regulated airflow.

o Placed the barrel in an outdoor space that is open and well-ventilated,

keeping it distant from combustible materials.

3. Loading the Rice Husk and Coconut Shell Separately

o Stacked the dried rice husk and pre-cut coconut shell inside the barrel

to allow even air distribution during combustion.

4. Ignition of Rice Husk and Coconut Shell Separately

o Ignited the lower section of the rice husk and coconut shell stack using

a blowtorch or kindling material.

o Ensured gradual and consistent ignition process to avoid flaming

combustion and encourage smoldering.

5. Cooling Phase
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o Let the barrel cool to ambient temperature to avoid the risk of

spontaneous ignition when exposed to air.

6. Extraction of Rice Husk Ash and Coconut Shell Ash Separately

o Removed the charred rice husk and coconut shell from the barrel using

gloves and tools.

o Ensured no hot embers were left behind to prevent the possibility of

burns or fire.

7. Pulverization

o Grinded the rice husk ash and coconut shell ash manually or

mechanically to produce a fine ash-like powder.

8. Sieving and Refinement

o Passed the ground material through a #200 sieve to achieve a

consistent and fine particle size suitable for concrete mixing.

9. Color Observation and Description

o The resulting ash is typically dark gray to black, indicating successful

carbonization and rich carbon content.

o Labeled and stored in a dry location until use in the concrete mix.

Preparing of Red Clay

1. Buying/Acquiring of Red Clay

o Obtain natural red clay from a reliable local deposit or site.

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o Dig a hole with a depth of 30-50 cm depending on the site conditions

and quality of the clay layer.

2. Washing

o Place the clay in a large container or basin.

o Soak in water.

o Stir the water to separate the clay from sand and any impurities.

o Let the mixture settle for a few minutes. Sand and heavy particles will

sink.

o Decant or pour off the clay-rich water.

o Let the fine clay settle.

3. Drying

o Spread the washed clay and dry it under sunlight for approximately

one week, ensuring complete moisture removal.

4. Grinding

○ Once dried, the clay is ground using appropriate equipment to achieve

fine particles suitable for blending.

5. Sieving

○ Passed the ground clay through a #200 sieve to ensure uniform particle

size to enhance its compatibility with cement and improves

performance in composites.
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Step-by-Step Process for Mixing Concrete Mix Designs

1. Material Preparation

1.1. Gather Materials

Collected necessary materials: Ordinary portland cement (OPC), fine

aggregates (sand), coarse aggregate (gravel), clean potable water, coconut

shell ash (CSA), rice husk ash (RHA), and red clay (RC).

1.2. Measure Quantities

Using a digital weighing scale, exact quantities of components were

measured in accordance with the predetermined mix ratio.

2. Selection of Mix Design

Choose the appropriate mix design: (DILI KO SURE)

● Mix A (Conventional Mix): 0% CSA, 0% RHA, and 0% RC

● Mix B: 10% CSA, 25% RHA, and 5% RC (Partial

Replacement)

● Mix C: 10% CSA, 20% RHA and 5% RC (Partial

Replacement)

● Mix D: 5% CSA, 15% RHA and 5% RC (Partial Replacement)

3. Dry Mixing

3.1. Combine Cement, CSA, RHA, RC, and aggregates

Mix the dry components—Cement, CSA, RHA, RC, sand, and gravel

—thoroughly for 2–3 minutes in a cleaned mixing tray or concrete mixer to

attain a uniform blend.

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3.2. Ensure Homogeneity

Checked the distribution of the CSA, RHA, and RC to ensure

uniformity and absence of clumping.

4. Wet Mixing

4.1. Add Water

While continually mixing, gradually add the liquid to the dry mixture.

4.2. Mix Thoroughly

Continue mixing for another 3-5 minutes to create a consistent,

workable concrete paste.

5. Workability Testing

5.1. Conduct Slump Test

Immediately conduct a slump test to determine the workability of each

mix design. If the drop in height is higher than desired, adjust the water.

The weight of each ingredient to be used in concrete mixtures was calculated

in accordance with the ACI 211.1-91 regulations and standards. Conventional

materials' physical parameters, including specific gravity, density, fineness

modulus, water content, and absorption, were required to determine the mixed

design. The first stage in determining the mix design was to establish the

water-cement ratio based on the concrete's intended compressive strength, as

given in table 3.4.

Water, kg/m3 of concrete for indicated nominal maximum sizes of

 57

Slump, mm aggregates
9 12.5 19 25 37.5 50 75 150
(mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm)
25 to 50
75 to 100
150 to 175
Approximate
amount of
entrapped air
in non-air
entrained
concrete in%

Slump Test Water Ratio

6. Molding

6.1. Lubricate Molds

To prevent sticking, apply lubrication oil to the mold surfaces.

6.2. Fill Molds in Layer

Poured the concrete into the molds in three equal layers, tamping each

layer 25 times with a tamper rod.

7. Finishing and Labeling

7.1. Surface Finishing

Leveled the top surface using a trowel.

7.2. Label Specimens

Clearly labeled each specimen based on its mix type and date.

8. Initial Curing
 58

8.1. Cover and Store

To avoid moisture loss, cover the molds with a damp towel or plastic

sheet.

8.2. Demolding

After 24 hours, remove the specimens from the molds and transfer

them to the curing tank.

9. Curing

9.1. Immerse in Water

Placed specimens in a curing tank with clean water at 23 ± 2°C.

10. Testing Schedule

10.1. Testing Schedule

No. of Days
Type of Mix
7 14 28

Conventional 4 samples 4 samples 4 samples

Mix A 4 samples 4 samples 4 samples

Mix B 4 samples 4 samples 4 samples

Mix C 4 samples 4 samples 4 samples

Table 3.5 Testing Schedule

Step-by-Step Process for Molding, Demolding, and Curing of Concrete

Specimens

1. Molding of Concrete Specimens

 59

1.1. Preparation of Molds

Carefully cleaned the molds to eliminate any dust, debris, or dried

concrete remnants.

1.2. Application of Lubricant Oil

Applied a uniform layer of form-release agent (lubricant oil) to the

inner surfaces of the molds to ensure they can be easily removed after setting.

1.3. Placement of Concrete in Molds

Divide the mixture into three equal layers for each mold using a scoop

or trowel. Make sure the mold dimensions adhere to ASTM specifications (for

instance, 150 mm × 150 mm × 150 mm cubes).

1.4. Tamping

Compacted each layer by tamping it 25 times using standard tamping

rod 25 times to remove air pockets and guarantee consistent density.

1.5. Surface Finishing

Leveled and smoothed the top surface of the sample using a steel

trowel to obtain a flat and uniform finish.

1.6. Identification and Labeling

Clearly mark each mold with a waterproof marker or tag to show the

mix type, batch number, and casting date.

2. Demolding of Specimens

2.1. Initial Curing

Cover the molds with moist burlap or plastic sheets and let them

remain undisturbed at room temperature for approximately 24 hours.

 60

2.2. Specimen Removal

After 24 hours, carefully remove the specimens from the molds to

avoid chipping or cracking.

2.3. Inspection

Visually examined every specimen for any surface flaws or

inconsistencies. Eliminate any defective samples to ensure the integrity of the

testing process.

3. Curing of Specimens

3.1. Curing Tank Preparation

Fill the curing tank with clean, potable water and maintain a constant

temperature of 23 ± 2°C, in accordance with ASTM C511.

3.2. Immersion of Specimens

Submerged the demolded specimens entirely in the curing tank to

guarantee thorough hydration of the cement matrix.

3.3. Curing Duration

Specimens were cured for 7, 14, and 28 days according to the

established testing timeline. Made sure that the specimens stayed fully

submerged during the entire duration.

3.4. Monitoring

Checked water levels and temperature every day to ensure stable

curing conditions. Refill or add water as necessary to keep samples fully

submerged.

Step-by-Step Process for Compressive Strength Testing and Data Analysis

 61

1. Compressive Strength Testing Procedure

1.1. Specimen Retrieval

Concrete specimens were carefully removed from the curing tank at

the appropriate curing ages (7, 14, and 28 days). Wipe away any excess

surface moisture with a clean cloth.

1.2. Inspection Prior to Testing

Visually examine each cube specimen (150 mm × 150 mm × 150 mm)

for surface defects, cracks, or signs of incorrect curing. Damaged specimens

are excluded from testing.

1.3. Dimensional Verification

To ensure uniformity and precision, measure the dimensions of each

specimen with a calibrated meter stick.

1.4. Position to UTM

Placed the specimen in the middle of the Universal Testing Machine's

(UTM) lower platen to ensure uniform contact across the base.

1.5. Loading Process

Applied a constant and uniform load without shock at a rate of 0.25

MPa/s to 0.35 MPa/s (per ASTM C39/C39M) until the specimen failed.

1.6. Record Maximum Load

Recorded the maximum load (P) at failure given by the UTM in

kilonewtons (kN).

1.7. Computation of Compressive Strength

 62

Calculated the compressive strength (𝜎) using the formula:

𝜎=P/A

Where:

𝜎 = Compressive strength (MPa)

P = Maximum applied load (N)

A = Cross-sectional area of the specimen (mm²)

2. Data Analysis Procedure

2.1. Data Tabulation

All compressive strength results were organized in a tabular format,

categorized by mix type (e.g., Mix A, B, C, D) and curing age.

2.2. Averaging of Values

The mean compressive strength was calculated for each specimen

group (usually four samples per group).

2.3. Standard Deviation and Variance

To evaluate data reliability and dispersion, we calculated the standard

deviation (SD) and coefficient of variation (CV).

2.4. Comparative Analysis

To investigate the impact of coconut shell ash (CSA), rice husk ash

(RHA), and red clay (RC), we compared compressive strength across various

mix designs and curing times.

2.5. Graphical Representation

 63

Plotted line or bar graphs to visually represent each mix's strength

progression over time. Use software such as Excel.

2.6. Statistical Testing (Optional)

ANOVA was used to evaluate if observed variations in compressive

strength are statistically significant at a certain confidence level (e.g., 95%).

2.7. Interpretation of Results

Analyzed trends, determined appropriate mix proportions, and reached

conclusions on the effects of BCA and SM on mechanical performance.

 64

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