The high global demand and a significant carbon footprint of around 8% of anthropogenic CO₂ emissions from the production of Portland cement, intensive research has been conducted on the use of supplementary cementitious materials (SCMs) from agricultural waste has been conducted. Cassava (Manihot esculenta Crantz) is a widely farmed staple food in the tropics, with an estimated amount of 20–35% of cassava tubers wasted as peel. In this review, the cassava peel ash (CPA) as a new Supplementary Cementitious Material (SCM) is critically discussed mainly regarding its physicochemical characterization, pozzolanic properties, and performance in cementitious systems.
Analysis of available literature shows that the typical CPA would contain 55.93% SiO₂, 19.88% Al₂O₃, and 6.02% Fe₂O₃ which equals a total content of pozzolanic oxides of 81.83%, which is much higher than the minimum of 70% prescribed in ASTM C618. According to the pozzolanic activity index (PAI) of CPA 75.8% is satisfactory pozzolanic reactivity. The optimum calcination temperature is 600–700°C which yields ash with a high amorphous silica content for pozzolanic reactions. Concrete with 5–15% CPA replacement has compressive strengths similar to those in control concrete at 28 days, and additional strength gain is promoted by the creation of secondary calcium-silicate-hydrate (C-S-H) formation in the concrete.
This review summarizes the current state of the art for CPA production methodologies, characterization techniques (XRF, XRD, SEM-EDS, FTIR), and how replacement levels affect the properties of fresh and hardened concrete. Moreover, it discusses standardization issues, environmental sustainability consequences and points out key research gaps preventing the commercialization of CPA for construction. The results justify the cassava peel waste valorisation as a realistic and eco-efficient SCM, especially on the African continent where the construction industry is highly developed and there is a wide range of cassava production areas.
Table of Contents
1. INTRODUCTION
1.1 Background and Context
1.2 The African Cassava Production Landscape.
1.3 The objectives of the Review
2. RELATED WORKS AND LITERATURE REVIEW
2.1 Agricultural Waste Ashes as Supplementary Cementitious Materials
2.2 A chronological overview of Cassava Peel Ash research is presented below.
2.3 The performance of pozzolanic materials under different conditions.
3. PRODUCTION AND PREPARATION OF CASSAVA PEEL ASH
3.1 Raw Material Sourcing and Pre-treatment
3.2 Calcination parameters and their effects.
3.3 Grinding and Particle Size Optimization
4. PHYSICOCHEMICAL CHARACTERIZATION OF CASSAVA PEEL ASH
4.1 Chemical Composition (XRF Analysis)
4.2 Mineralogical Characterization (XRD Analysis)
4.3 Morphological Characterization (SEM-EDS)
4.4 The thermal and spectroscopic characteristics.
5. POZZOLANIC ACTIVITY OF CASSAVA PEEL ASH
5.1 Theoretical Framework of Pozzolanic Reactions
5.2 Pozzolanic Activity Index (PAI).
5.3. Frattini Test and Lime Reactivity.
6. PERFORMANCE IN CEMENTITIOUS SYSTEMS
6.1 Fresh Concrete Properties
6.2 Compressive Strength Development
6.3 Durability Properties
6.4 Microstructural Evolution
7. ENVIRONMENTAL SUSTAINABILITY AND LIFE-CYCLE IMPLICATIONS
7.1 Carbon Footprint Reduction
7.2 Waste management and circular economy
7.3 Life-Cycle Assessment Considerations
8. RESEARCH GAPS AND FUTURE DIRECTIONS
8.1 Critical Research Priorities
8.2 Standardisation and Regulatory Issues.
8.3 Emerging Applications and Innovations
9. CONCLUSION
Objectives & Topics
The primary aim of this scientific review is to comprehensively examine the viability of cassava peel ash (CPA) as an eco-efficient supplementary cementitious material (SCM) to decarbonize the cement sector and resolve agricultural waste challenges, focusing on how its chemical, physical, and thermal properties determine its pozzolanic performance and durability in concrete systems.
- Thermal transformation and optimization parameters for producing reactive amorphous silica from cassava peel waste.
- Physicochemical and mineralogical characterization using XRF, XRD, SEM-EDS, and FTIR techniques.
- Evaluation of pozzolanic activity indices and compliance with ASTM C618 standards for natural pozzolans.
- Mechanical behavior, workability, hydration kinetics, and durability characteristics of CPA-blended concrete.
- Environmental life-cycle analysis, carbon footprint reduction, and circular economy implications across Africa.
- Standardization challenges, regulatory pathways, and emerging innovations such as geopolymers and 3D printing.
Excerpt from the Book
3.2 Calcination parameters and their effects.
Cassava peels are burned in a controlled manner (calcined) and the most critical process in the production of CPA determines the quality of ash, amorphous silica content and pozzolanic reactivity is the temperature and duration of the burning. As shown in Figure 5, the correspondence between the temperature of the calcination and the amorphous silica content and the pozzolanic activity index is drawn.
An optimum calcination temperature range has been found to be 600-700 °C and a holding time of 90 minutes to 3 hours [28, 29]. If the temperature is below 500°C, the organic matter is not fully burned and the loss on ignition (LOI) is high and the pozzolanic activity is less. XRD analysis of the CPA calcined at 450°C showed the presence of high peaks of quartz (crystalline silica) and small peaks of amorphous silica, which resulted in the lower values of PAI [30].
Decomposition of cellulose and lignin is complete at 600–700°C and at this stage, the silica will be converted from the crystalline to amorphous form, which is essential for pozzolanic reactivity [28]. The XRD pattern of CPA calcinated at 600°C shows the presence of both crystalline peaks (quartz and sodalite) and a broad amorphous hump peaking at 20-30° 2θ, which is indicative of the presence of reactive silica [29]. SEM image shows that the particles have irregular shape with deep crevices and microporosity which produces a large surface area available for pozzolanic reactions [29].
Sintering and recrystallization of silica will begin at temperatures above 800°C, which will decrease the amorphous content and therefore the pozzolanic activity [28]. This thermal degradation phenomenon is common for all the agricultural waste ashes and further demonstrates the need to precisely control the temperature during the CPA production.
Chapter Summary
1. INTRODUCTION: Explores the environmental burden of cement production, the need for low-carbon SCMs, and the vast cassava cultivation across Africa that produces millions of tonnes of unutilized peel waste.
2. RELATED WORKS AND LITERATURE REVIEW: Reviews agro-waste ashes in construction, compares CPA with rice husk and sugarcane bagasse ash, and outlines the chronological progression of CPA research since 2015.
3. PRODUCTION AND PREPARATION OF CASSAVA PEEL ASH: Details sourcing, pretreatment methods including drying and milling, and the precise thermal control needed during calcination to optimize reactivity and fineness.
4. PHYSICOCHEMICAL CHARACTERIZATION OF CASSAVA PEEL ASH: Analyzes the chemical oxide ratios via XRF, crystal structures via XRD, micromorphology via SEM-EDS, and functional bonding via thermal and FTIR spectroscopy.
5. POZZOLANIC ACTIVITY OF CASSAVA PEEL ASH: Discusses the secondary hydration reaction forming C-S-H gel, evaluates Pozzolanic Activity Index (PAI) results against ASTM C618 standards, and assesses lime consumption kinetics.
6. PERFORMANCE IN CEMENTITIOUS SYSTEMS: Investigates the fresh properties, 28-day and 90-day compressive strength, flexural resistance, durability against sulfates and chlorides, and microstructural densification.
7. ENVIRONMENTAL SUSTAINABILITY AND LIFE-CYCLE IMPLICATIONS: Quantifies CO₂ mitigation potential, life-cycle impact categories, and circular economy advantages of diverting decomposing peels from landfills into valuable construction inputs.
8. RESEARCH GAPS AND FUTURE DIRECTIONS: Outlines the missing production standards, limited long-term durability data in tropical climates, techno-economic considerations, and cutting-edge uses in soil stabilization and geopolymers.
9. CONCLUSION: Synthesizes evidence confirming CPA as a viable supplementary cementitious material while setting out actionable regulatory and research roadmaps required for widespread industry commercialization.
Keywords
Cassava peel ash, supplementary cementitious material, pozzolanic activity index, decarbonization, amorphous silica, calcination, compressive strength, durability, circular economy, hydration kinetics, XRF analysis, SEM-EDS
Frequently Asked Questions
What is the central focus of this scientific publication?
The review investigates the physicochemical characteristics, pozzolanic reactivity, and mechanical and durability performance of cassava peel ash (CPA) when utilized as a supplementary cementitious material to partially replace ordinary Portland cement.
What are the core thematic areas explored throughout the review?
The core themes include agro-waste valorization, thermal calcination optimization, mineralogical and spectroscopic characterization, cement hydration chemistry, mechanical performance in concrete, and environmental life-cycle sustainability.
What is the primary objective of the authors' research?
The primary objective is to evaluate whether cassava peel waste can be transformed into a standardized, high-performance pozzolan that substantially lowers the carbon footprint of concrete construction, particularly within developing African economies.
Which scientific methods and characterization tools are employed?
The reviewed findings rely on experimental methods including X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and standard pozzolanic testing such as ASTM C618 and the Frattini test (EN 196-5).
What does the main body of the document evaluate regarding concrete performance?
The main sections evaluate fresh mixture properties such as workability and setting retardation, compressive and flexural strength development up to 90 days, resistance to sulfate and chloride attacks, carbonation susceptibility, and interfacial transition zone densification.
Which keywords best summarize the scope of this study?
The study is characterized by keywords including Cassava peel ash, supplementary cementitious material, pozzolanic activity, calcination temperature, amorphous silica, compressive strength, durability, microstructural evolution, and environmental sustainability.
What is the optimal calcination temperature identified for producing reactive CPA?
The optimal calcination range is between 600°C and 700°C for a retention time of 90 minutes to 3 hours, which fully burns organic lignin and cellulose to generate reactive amorphous silica while preventing crystalline recrystallization that begins above 800°C.
How does CPA concrete perform in terms of compressive strength and replacement limits?
At replacement levels of 5% to 15%, CPA concrete achieves 28-day compressive strengths comparable to conventional control concrete, and demonstrates superior long-term strength gains at 90 days as secondary calcium-silicate-hydrate (C-S-H) gels form and fill microcapillary pores.
What are the primary barriers preventing the immediate commercial use of CPA in the building sector?
Key hurdles include the absence of standardized calcination and production protocols, insufficient long-term durability data under cyclic tropical climates, lack of formal recognition by national building codes and standards bodies, and the need for large-scale field demonstration projects.
- Quote paper
- Olabimtan Olabode et al. (Author), 2026, Cassava Peel Ash as a Supplementary Cementitious Material, Munich, GRIN Verlag, https://www.grin.com/document/1760574
