Investigation of Sugarcane Bagasse Ash as a Supplementary Cementitious Material

Investigation of Sugarcane Bagasse Ash as a Supplementary Cementitious Material
Abstract
Sugarcane bagasse ash (SCBA) is an agricultural by-product generated in large quantities by the sugar industry, offering significant potential as a supplementary cementitious material (SCM) for sustainable concrete production. This study investigates the viability of SCBA as a partial replacement for Ordinary Portland Cement through comprehensive analysis of its chemical composition, pozzolanic reactivity, and effect on concrete properties. Findings demonstrate that SCBA contains high amorphous silica content (50–80% SiO₂), with combined SiO₂, Al₂O₃, and Fe₂O₃ exceeding 70%, satisfying ASTM C618 requirements for pozzolanic materials . Controlled combustion at 600–700°C significantly enhances pozzolanic reactivity, with controlled ash achieving 82.4% amorphous silica content and 60–70% portlandite consumption . Optimal replacement levels range from 5% to 15%, with 10% consistently yielding the best balance of strength and durability performance . At 10% replacement, SCBA concrete achieves compressive strength improvements of up to 33%, with substantial durability enhancements including 43% reduction in chloride permeability and improved sulfate and acid resistance . However, excessive replacement beyond 15–20% leads to strength reduction due to dilution effects . The study concludes that SCBA is a viable SCM when used at appropriate replacement levels, contributing to sustainable construction while addressing agricultural waste management challenges.
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CHAPTER ONE: INTRODUCTION
1.1 Background of the Study
Concrete is the most extensively used construction material globally, with its production heavily dependent on Portland cement. The cement industry accounts for approximately 7% of global carbon dioxide emissions, creating substantial environmental pressure to reduce clinker content in concrete . Simultaneously, the sugar industry generates enormous quantities of sugarcane bagasse as a by-product, which upon combustion produces sugarcane bagasse ash (SCBA), presenting disposal challenges and environmental concerns .
SCBA is a residual waste from bagasse incineration for power generation in the sugar industry. While commonly used as fertilizer in sugarcane plantations, SCBA provides limited mineral nutrients and carries potential risks of contaminating soil and water sources . The incorporation of SCBA into cement-based composites has emerged as a promising solution, with experimental studies demonstrating favorable results .
The pozzolanic reactivity of SCBA is fundamentally attributed to the amorphous SiO₂ present in the ash, which undergoes secondary hydration reactions with calcium hydroxide from cement hydration to form additional calcium silicate hydrate (C-S-H) gel . Research has consistently demonstrated that controlled combustion and adequate grinding substantially enhance SCBA pozzolanic activity, resulting in improved workability and reduced permeability in concrete mixtures .
1.2 Statement of the Problem
Despite the recognized potential of SCBA as a supplementary cementitious material, several challenges hinder its widespread adoption. The quality and pozzolanic reactivity of SCBA vary considerably depending on combustion conditions, with uncontrolled mill combustion producing inconsistent quality and limited pozzolanic reactivity . The absence of controlled combustion studies systematically correlating processing conditions to ash microstructure and concrete performance represents a critical research gap .
Furthermore, the optimal replacement level of SCBA varies across studies, with reported optima ranging from 5% to 20% depending on ash characteristics, mix design, and performance criteria . This variability creates uncertainty for practical mix design. The relationship between SCBA replacement level and strength development at different curing ages also requires clarification, as SCBA concrete typically exhibits reduced early-age strength but enhanced long-term performance .
1.3 Aim and Objectives of the Study
1.3.1 Aim
The aim of this study is to investigate the suitability of sugarcane bagasse ash as a supplementary cementitious material in concrete, with particular emphasis on its pozzolanic characteristics and effect on mechanical and durability properties.
1.3.2 Objectives
The specific objectives of this research are:
1. To examine the chemical composition and pozzolanic characteristics of sugarcane bagasse ash.
2. To determine the optimal SCBA replacement level for maximum performance.
3. To assess the influence of combustion conditions on SCBA quality and reactivity.
4. To evaluate mechanical properties development at various curing ages.
5. To provide practical recommendations for SCBA utilization in sustainable concrete production.
1.4 Research Questions
This study seeks to answer the following research questions:
1. Does sugarcane bagasse ash possess the chemical composition and pozzolanic properties required for use as a supplementary cementitious material?
2. What is the optimal replacement percentage of cement with SCBA for concrete performance?
3. How do combustion conditions influence SCBA quality and pozzolanic reactivity?
4. How does SCBA replacement affect mechanical and durability properties?
5. What are the practical implications of SCBA utilization for sustainable construction?
1.5 Significance of the Study
This research holds significance for multiple stakeholders. For civil engineers and concrete technologists, understanding the optimal SCBA replacement level enables informed mix design decisions that balance performance and sustainability. For the construction industry, the findings contribute to reducing cement consumption and associated carbon emissions. For the sugar industry, the study supports beneficial utilization of an abundant by-product, addressing disposal challenges. The research also aligns with circular economy principles that emphasize resource efficiency and waste valorization .
1.6 Scope and Limitations of the Study
1.6.1 Scope
This study focuses on the investigation of SCBA as a supplementary cementitious material in concrete. The investigation covers:
• Chemical composition and pozzolanic characteristics of SCBA.
• Influence of combustion conditions on SCBA quality.
• Optimal replacement levels for SCBA in concrete.
• Mechanical properties development at various curing ages.
• Durability characteristics including permeability and chemical resistance.
1.6.2 Limitations
The study is primarily based on a review of existing literature and does not include original laboratory experimental work. The focus is on compressive strength as the primary mechanical indicator, though other properties are discussed where relevant. The investigation is limited to normal-strength concrete and does not comprehensively address high-performance or specialty concrete applications.
1.7 Definition of Terms
Sugarcane Bagasse Ash (SCBA): A pozzolanic material produced by burning sugarcane bagasse, the fibrous residue remaining after juice extraction from sugarcane .
Pozzolanic Reaction: The chemical reaction between reactive silica in SCBA and calcium hydroxide from cement hydration to form calcium silicate hydrate (C-S-H) gel.
Controlled Combustion: The burning of bagasse under regulated temperature and airflow conditions to optimize amorphous silica content and pozzolanic reactivity .
Supplementary Cementitious Material (SCM): A material that, when used in conjunction with Portland cement, contributes to the properties of hardened concrete through hydraulic or pozzolanic activity.
Amorphous Silica: Non-crystalline silicon dioxide with high reactivity, essential for pozzolanic activity.
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CHAPTER TWO: LITERATURE REVIEW
2.1 Introduction
This chapter reviews existing literature on the use of sugarcane bagasse ash as a supplementary cementitious material and its effect on concrete properties. The review examines the production and characteristics of SCBA, the pozzolanic reaction mechanism, the influence of SCBA on fresh and hardened concrete properties, and optimal replacement levels reported in the literature.
2.2 Sugarcane Bagasse Ash: Production and Characteristics
2.2.1 Production Process
SCBA is produced by burning sugarcane bagasse, the fibrous residue remaining after juice extraction from sugarcane. The combustion conditions significantly influence the properties of the resulting ash. Research has employed various calcination regimes, with controlled combustion at 600–700°C with regulated airflow demonstrating superior pozzolanic reactivity compared to uncontrolled mill combustion .