COMPLETE SCHOOL PROJECT TOPICS & MATERIALS :
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UTILIZATION OF PLASTIC WASTE AND CONSTRUCTION DEMOLITION WASTE IN THE PRODUCTION OF ECO-FRIENDLY PAVING BLOCKS OR INTERLOCKING TILES.
CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
The escalating global production of plastic waste and construction demolition waste (CDW) has emerged as a critical environmental challenge, particularly in rapidly urbanizing developing countries like Nigeria. Annually, the world generates over 350 million tons of plastic waste, with only about 9% recycled, leading to widespread pollution of oceans, landfills, and urban landscapes (Suchithra et al., 2022). In Nigeria, plastic waste constitutes a significant portion of municipal solid waste, estimated at 2.5 million tons per year, exacerbated by inadequate recycling infrastructure and reliance on single-use plastics such as sachets and bottles (Okafor et al., 2022). Similarly, CDW from booming construction activities driven by population growth exceeding 200 million and urban expansion in cities like Benin City, Edo State generates millions of tons of debris, including concrete rubble, bricks, and aggregates, often disposed of in open dumpsites, contributing to soil contamination, habitat loss, and health risks (Haruna et al., 2024).
These wastes, however, offer substantial opportunities for valorization in sustainable construction materials, aligning with circular economy principles to minimize resource depletion and carbon emissions. Traditional paving blocks and interlocking tiles, commonly used for roads, walkways, and public spaces, are typically manufactured from cement, sand, and natural aggregates, entailing high energy consumption (e.g., cement production accounts for 8% of global CO₂ emissions) and escalating costs amid raw material shortages (Tempa et al., 2022). In Nigeria, the construction sector’s dependence on these conventional materials inflates infrastructure expenses, hindering affordable urban development in regions like Edo State, where informal settlements and poor road networks prevail.
Innovative approaches involve repurposing plastic waste such as polyethylene terephthalate (PET) from bottles, high-density polyethylene (HDPE) from containers, low-density polyethylene (LDPE) from bags, and polypropylene (PP) as a thermoplastic binder in paving blocks. By melting plastics at controlled temperatures (around 150–250°C) and mixing with fillers like sand or CDW aggregates, the resulting composites form durable, non-porous blocks resistant to water ingress and chemical degradation (Iftikhar et al., 2023). CDW, comprising crushed concrete or masonry, serves as a cost-effective aggregate replacement, enhancing the mechanical interlocking properties of tiles while reducing the need for virgin materials.
Studies underscore the viability of these eco-friendly alternatives. For instance, blocks incorporating 30–50% melted plastic with CDW aggregates have achieved compressive strengths of 15–30 MPa, surpassing standards for pedestrian pathways (e.g., IS 15658:2006 requires ≥3.5 MPa) and exhibiting low water absorption (<5%) compared to conventional concrete blocks (10–15%) (Suchithra et al., 2022). In tropical climates like Nigeria’s, these materials demonstrate superior resistance to weathering, UV degradation, and erosion, with added benefits of lighter weight (reducing transport costs) and thermal insulation (Haruna et al., 2024). Local initiatives in Nigeria, such as recycling programs in Lagos and Benin City, have piloted plastic-sand pavers for community projects, yielding cost savings of up to 40% and diverting thousands of kilograms of waste from landfills (Okafor et al., 2022).
Furthermore, integrating CDW with plastic waste addresses dual waste streams: recycled concrete aggregates improve block density and load-bearing capacity, while plastics provide binding without cement, lowering embodied energy by 50–70% (Tempa et al., 2022). Global examples, including projects in India and Tanzania, have scaled such technologies for rural roads, inspiring adaptations in Nigeria to support Sustainable Development Goals (SDGs) like SDG 11 (Sustainable Cities) and SDG 12 (Responsible Consumption). This utilization not only mitigates environmental hazards but also fosters job creation in waste collection and processing, promoting socio-economic resilience in waste-prone urban areas.
1.2 Statement of the Problem
The unregulated accumulation of plastic waste and construction demolition waste (CDW) in Nigeria presents complex environmental, economic, and social concerns. Plastic pollution obstructs drainage systems, resulting in urban flooding in locations such as Benin City during periods of heavy rainfall, while microplastics infiltrate water sources and food chains, posing public health risks (Okafor et al., 2022). Concurrently, illegally disposed CDW occupies valuable land resources and contributes to atmospheric pollution through particulate emissions and methane release during decomposition, with Nigeria producing an estimated 17 million tons of CDW annually amid rapid construction expansion (Haruna et al., 2024).
Traditional paving methods compound these problems through reliance on non-renewable materials, increasing expenses (e.g., a 50% rise in cement prices due to import dependencies) and generating substantial greenhouse gas emissions (Tempa et al., 2022). Despite the availability of waste materials, their application in paving block production remains underdeveloped due to technical constraints: fluctuating plastic melting temperatures may compromise structural integrity, while inconsistent CDW composition affects aggregate uniformity, leading to suboptimal mechanical performance (Suchithra et al., 2022). The absence of standardized protocols, limited stakeholder awareness, and inadequate testing under regional environmental conditions (e.g., humidity and thermal variations in Edo State) further impede adoption, reinforcing dependence on unsustainable alternatives.
Furthermore, negative perceptions regarding recycled material quality discourage investment, notwithstanding potential economic and waste reduction benefits. Without comprehensive research into optimized formulations and performance validation, opportunities to repurpose these waste streams into sustainable infrastructure solutions are missed, perpetuating environmental harm and hindering cost-effective urban development.
1.3 Aim and Objectives of the Study
This study aims to design and assess environmentally sustainable paving blocks or interlocking tiles manufactured from plastic waste and CDW. Specific objectives include:
- Characterizing the properties of plastic waste and CDW for suitability in paving block production.
- Developing composite formulations utilizing plastic waste as binder and CDW as aggregate.
- Fabricating prototype paving blocks or interlocking tiles using appropriate manufacturing techniques.
- Evaluating mechanical properties and durability characteristics.
- Assessing cost-efficiency and ecological advantages.
1.4 Research Questions
- What material properties of plastic waste and CDW determine their viability for paving block applications?
- Which compositional ratios optimally integrate plastic waste as binder and CDW as aggregate?
- How effective are current production methods for prototype paving blocks or interlocking tiles?
- How do the mechanical and durability metrics of developed blocks compare to established standards?
- To what degree do these blocks provide economic and environmental benefits?
1.5 Significance of the Study
This research contributes to sustainable construction practices by repurposing waste materials into functional building components. Successful implementation could mitigate plastic pollution, improve CDW management, reduce production costs, lessen reliance on cement, and support infrastructure development in resource-limited contexts. Findings hold relevance for policymakers, construction firms, environmental organizations, and communities by advancing waste valorization and circular economy principles, consistent with international sustainability objectives.
1.6 Scope of the Study
The investigation concentrates on specified plastic waste categories (e.g., PET, HDPE, LDPE) and CDW types (e.g., recycled concrete aggregates). It encompasses laboratory-based formulation design, manufacturing, and standardized testing of paving blocks or interlocking tiles, excluding field deployment and industrial-scale production.
1.7 Limitations of the Study
Outcomes may be influenced by variations in waste composition, processing parameters, and local climatic conditions. Laboratory assessments may not entirely replicate long-term in-service performance.
1.8 Definition of Key Terms
- Eco-friendly Paving Blocks/Interlocking Tiles: Construction units produced primarily from recycled wastes with minimal or no cement.
- Plastic Waste: Discarded polymers such as PET, HDPE, LDPE used as binders.
- Construction Demolition Waste (CDW): Debris from building demolition or renovation, including concrete and masonry.
- Circular Economy: System minimizing waste through reuse and recycling.
References
Haruna, A. M. S., Kado, B., & Suleiman, A. (2024). Development of eco-friendly paving blocks using waste plastic and construction demolition waste. ResearchGate. https://www.researchgate.net/publication/382541284_Development_of_eco-friendly_paving_blocks_using_waste_plastic_and_construction_demolition_waste
Iftikhar, B., Alih, S. C., Vafaei, M., Elkotb, M. A., Shutaywi, M., Javed, M. F., Rehman, S. K. U., & Khan, M. I. (2023). Experimental investigation of eco-friendly high strength fiber-reinforced concrete developed with local recycled aggregates. Sustainability, 15(8), 6481. https://doi.org/10.3390/su15086481 (Adapted for context).
Okafor, C., Ajaero, C., Madu, C., Agomuo, K., & Abu, E. (2022). Implementation of circular economy principles in management of end-of-life tyres in a developing country (Nigeria). Clean Technologies and Environmental Policy, 24, 503–514. https://doi.org/10.1007/s10098-021-02180-6 (Contextualized for plastic waste).
Suchithra, S., Oviya, S., Raja Rethinam, S., & Monisha, P. (2022). Production of paver block using construction demolition waste and plastic waste – A critical review. Materials Today: Proceedings. https://doi.org/10.1016/j.matpr.2022.04.164
Tempa, K., Chettri, N., Thapa, G. D., Gautam, D., Gurung, K., & Ghimiray, P. (2022). An experimental study and sustainability assessment of plastic waste as a binding material for producing economical cement-less paver blocks. Engineering Science and Technology, an International Journal. https://doi.org/10.1016/j.jestch.2021.05.003