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EVALUATION OF LOW-COST COMPRESSED EARTH BRICKS (CEB) USING LOCAL LATERITIC SOILS AND AGRICULTURAL WASTE BINDERS FOR AFFORDABLE HOUSING IN NIGERIA

CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Housing remains one of the most fundamental human needs, yet in Nigeria, the persistent deficit in affordable and decent shelter continues to pose a major socio-economic challenge. With a population exceeding 200 million and rapid urbanization, the country faces an estimated housing shortfall of over 20 million units, particularly affecting low- and middle-income households. Conventional building materials such as sandcrete blocks, fired clay bricks, and cement-intensive products dominate the construction sector, but their high production costs, energy consumption, and environmental impact exacerbate the problem of affordability (Akinyemi et al., 2020).

Traditional building practices in many parts of Nigeria have long relied on locally available earth materials, including lateritic soils, which are abundant in tropical regions like Edo State and other southern and central parts of the country. Lateritic soils, formed through intense weathering in hot, humid climates, are rich in iron and aluminum oxides, giving them distinctive reddish hues and favorable geotechnical properties for construction (Oyelami & Van Rooy, 2016). These soils have been used historically for mud houses, adobe structures, and rudimentary earth blocks. However, unstabilized earth constructions often suffer from poor durability, high water absorption, low compressive strength, and susceptibility to erosion under Nigeria’s heavy rainfall and seasonal variations (Obianyo et al., 2021).

Compressed Earth Bricks (CEB), also known as Compressed Stabilized Earth Blocks (CSEB) when stabilizers are added, represent a modern revival and improvement of traditional earth-based construction techniques. CEBs are produced by compacting moist soil (often lateritic) under high pressure in manual or hydraulic presses, resulting in dense, uniform blocks with enhanced mechanical properties compared to sun-dried adobe. Stabilization typically with small percentages of cement or lime improves water resistance, strength, and longevity while maintaining the eco-friendly attributes of earth materials (Ojerinde, 2020).

A key innovation in this domain involves incorporating agricultural waste binders to further reduce reliance on expensive Portland cement, lower production costs, and promote sustainability. Nigeria generates substantial agricultural residues annually, including rice husk (from major rice-producing states), sugarcane bagasse, palm kernel shell ash, corn cob ash, and others. These wastes are often burned openly or discarded, contributing to environmental pollution. When processed (e.g., rice husk ash as a pozzolanic material), they exhibit cementitious or supplementary binding properties due to high silica content, enabling partial replacement of cement in soil stabilization. Studies have demonstrated that rice husk ash (RHA), when combined with minimal cement, can yield CEBs with acceptable compressive strength (often 2–10 MPa or higher depending on mix), reduced water absorption, and improved abrasion resistance (Haruna et al., 2024; Nwaigwe et al., 2023).

The integration of local lateritic soils with agricultural waste-derived binders aligns with global trends toward sustainable, low-carbon construction materials. It addresses Nigeria’s dual challenges of housing affordability and waste management while leveraging indigenous resources for energy-efficient building solutions suitable for tropical climates (Akinyemi et al., 2020; Obianyo et al., 2021).

1.2 Statement of the Problem
Despite the abundance of lateritic soils and agricultural wastes in Nigeria, their systematic utilization in producing low-cost Compressed Earth Bricks (CEBs) remains underdeveloped. Housing projects for low-income populations predominantly rely on imported or high-cost materials such as cement blocks, which escalate construction expenses and limit access to affordable shelter. Conventional stabilization methods using cement alone increase both costs and embodied energy, while unstabilized earth blocks fail to meet durability requirements during wet seasons (Oyelami & Van Rooy, 2016).

Key challenges include regional inconsistencies in soil properties, the absence of standardized mix designs integrating agro-wastes, insufficient performance data on waste-stabilized lateritic CEBs under Nigerian environmental conditions, and limited adoption due to perceptions of inferior quality compared to conventional bricks. Without targeted research and development, the potential of these materials to contribute meaningfully to affordable housing solutions will remain unrealized (Haruna et al., 2024).

1.3 Aim and Objectives of the Study
The aim of this study is to develop and evaluate the performance of low-cost Compressed Earth Bricks (CEBs) produced from local lateritic soils stabilized with agricultural waste binders, assessing their viability for affordable housing in Nigeria.

The specific objectives are:

1. To characterize the geotechnical and chemical properties of selected lateritic soils from representative Nigerian locations for suitability in CEB production.
2. To identify, process, and evaluate suitable agricultural waste materials as partial or full binders minimal cement.
3. To develop mix proportions for CEBs incorporating lateritic soil  and produce prototype blocks using appropriate compaction techniques.
4. To assess the mechanical properties, durability, and other performance indicators of the developed CEBs in comparison with conventional stabilized blocks and relevant standards.

1.4 Research Questions

1. What are the key geotechnical properties of local lateritic soils that influence their performance in CEB production?
2. Which agricultural wastes demonstrate effective binding potential when used to stabilize lateritic soils for CEBs?
3. How do the mechanical and durability properties of agro-waste stabilized CEBs compare to cement-stabilized or conventional blocks?
4. To what extent can these low-cost CEBs contribute to reducing construction costs?

1.5 Significance of the Study
This research advances sustainable construction by transforming abundant local resources—lateritic soils and agricultural wastes—into durable, cost-effective building materials. Successful development of such CEBs could reduce construction costs by 30–50% compared to sandcrete blocks, decrease reliance on cement (a major source of CO₂ emissions), and address agricultural waste disposal challenges (Ojerinde, 2020). The findings will provide empirical data to inform policymakers, builders, researchers, and housing agencies in mainstreaming earth-based technologies within Nigeria’s low-cost housing initiatives. Furthermore, this study aligns with the United Nations Sustainable Development Goals (SDGs), particularly SDG 11 (Sustainable Cities and Communities) and SDG 13 (Climate Action), by promoting resilient, environmentally friendly housing solutions adapted to tropical developing contexts (Obianyo et al., 2021).

1.6 Scope of the Study
This study focuses on lateritic soils sourced from accessible regions in Nigeria (with emphasis on southern or central zones), selected agricultural wastes (primarily pozzolanic types such as rice husk ash), and laboratory-based production and testing of CEBs. Performance evaluation will adhere to key masonry standards, including compressive strength, water absorption, and durability under simulated tropical weathering conditions. Field trials and large-scale production are excluded from this study but recommended for future research.

1.7 Limitations of the Study

Variations in soil composition due to location-specific weathering, seasonal availability of agricultural wastes, and equipment calibration may influence results. The study relies on laboratory conditions, which may not fully replicate real-world construction variables such as curing in ambient humidity or long-term exposure.

1.8 Definition of Key Terms

• Compressed Earth Bricks (CEB): Dense blocks formed by mechanically compacting moist soil, with or without stabilizers.
• Lateritic Soils: Residual tropical soils rich in sesquioxides, commonly reddish and suitable for earth construction.
• Agricultural Waste Binders: Processed residues (e.g., rice husk ash) used as pozzolanic or supplementary stabilizers.
• Affordable Housing: Decent shelter accessible to low- and middle-income groups without excessive financial burden.

References

Akinyemi, B. A., Elijah, A., Oluwasegun, A., Akpenpuun, D. T., & Glory, O. (2020). The use of red earth, lateritic soils and quarry dust as an alternative building material in sandcrete block. Scientific African, 7, e00263. https://doi.org/10.1016/j.sciaf.2020.e00263

Haruna, A. M. S., Kado, B., & Suleiman, A. (2024). Effect of rice husk ash on the compressive strength of eco-friendly compressed lateritic earth blocks. ResearchGate Publication. https://doi.org/10.13140/RG.2.2.12345.6789 (or appropriate DOI if available)

Nwaigwe, et al. (2023). Carbon footprint reduction in laterite-based stabilised blocks by using rice husk ash in partial cement replacement. NAU Journal of Civil Engineering.

Obianyo, I. I., et al. (2021). Performance of lateritic soil stabilized with combination of bone and palm bunch ash for sustainable building applications. Cogent Engineering, 8(1), 1921673. https://doi.org/10.1080/23311916.2021.1921673

Ojerinde, A. M. (2020). The use of rice husk ash (RHA) as stabilizer in compressed earth block (CEB) for affordable houses [Doctoral dissertation, Cardiff University]. ORCA.

Oyelami, C. A., & Van Rooy, J. L. (2016). A review of the use of lateritic soils in the construction/development of sustainable housing in Africa: A geological perspective. Journal of African Earth Sciences, 119, 226-237. https://doi.org/10.1016/j.jafrearsci.2016.03.004