Implementation of Construction and Demolition Wastes into Circular Economy Model

Abstract

The construction industry faces significant challenges as its dependence on traditional materials and practices continues to exacerbate environmental and economic pressures. Ordinary Portland cement (OPC), a cornerstone of modern construction, is a particularly problematic material due to its resource-intensive production process and substantial carbon emissions. Simultaneously, the sector generates enormous amounts of construction and demolition waste (CDW), much of which is landfilled without recovery, contributing to environmental degradation and resource depletion. Addressing these interlinked issues requires a strategic paradigm shift towards a circular economy model that prioritizes waste reduction, material recovery, and the development of sustainable alternatives to traditional construction materials. By transforming CDW into high-value materials and reducing reliance on OPC through innovative materials and processes, the construction industry can achieve significant environmental benefits, mitigate resource depletion, and align with global sustainability goals.

In response to aforementioned challenges, this thesis focuses on the transformation of CDWs into high-value secondary building materials, offering a detailed exploration of their structural performance, environmental impacts, cost-effectiveness, and practical application through case studies. The study begins by characterizing CDW-based materials sourced from various regions, considering the heterogeneity of these materials in terms of composition and properties. This in-depth analysis serves as the foundation for the development of new-generation Eco-hybrid cement concretes, which incorporate up to 87.5% CDW by mass. These novel materials were subjected to rigorous testing to evaluate their physical, mechanical, durability, and microstructural properties. The environmental impacts of these materials were then assessed through comprehensive life cycle assessment (LCA), comparing with CDW-based geopolymer concretes and conventional Portland cement concrete. The LCA results revealed significant reductions in global warming potential, acidification, and other environmental indicators for CDW-based concretes, highlighting their potential as a more sustainable alternative to traditional concrete.

The research then progresses to a higher technological readiness level, moving from laboratory experiments to real-time applications. It evaluates different CDW management strategies, comparing them with conventional demolition and construction methods from both environmental and economic perspectives. The integration of digital tools such as Building Information Modeling plays a crucial role in improving the efficiency of CDW sorting and waste flow during demolition. The final stage of this research culminates in the real-time construction of a single-story residential building using Eco-hybrid cement concrete, which serves as a demonstration of the large-scale, practical application of CDW-based materials. This real-world application bridges the gap between theoretical research and industry implementation, showcasing the feasibility of utilizing CDW in construction.

Overall, this thesis offers a valuable roadmap for integrating circular economy principles into the construction sector, demonstrating how CDW-based materials can contribute to achieving sustainability goals. By addressing key issues related to waste management, material recovery, and the environmental impact of traditional building materials, the research provides practical insights and strategies for promoting circularity and sustainability in the built environment. The success of this work not only advances academic knowledge but also offers concrete solutions for industry stakeholders, making a significant contribution to the global efforts toward a more sustainable construction sector.