CHALLENGES, OPPORTUNITIES, AND CIRCULAR ECONOMY PATHWAYS FOR CONCRETE AND CONSTRUCTION WASTE MANAGEMENT: EVIDENCE FROM URBAN BUILDING PROJECTS IN KARACHI, PAKISTAN

Abstract

The rapid expansion of urban construction activities in Karachi has led to a significant increase in construction and demolition waste, creating environmental, economic, and resource management challenges. In addition to conventional concrete debris, large volumes of secondary waste streams such as sewage sludge, plastic waste, waste glass, and tyre rubber remain underutilized despite their potential for value recovery. This study explores the challenges, opportunities, and circular economy pathways for integrated waste management in urban building projects in Karachi. Key challenges identified include the absence of effective waste segregation systems, limited recycling infrastructure, weak regulatory enforcement, and low market acceptance of recycled construction materials. However, these waste streams offer significant opportunities when incorporated into construction materials. Recycled concrete aggregates can replace natural aggregates, while processed sewage sludge ash can act as a supplementary cementitious material. Similarly, plastic waste, waste glass, and tyre rubber can be utilized to enhance concrete properties such as durability, thermal insulation, and crack resistance, contributing to sustainable material innovation.

The study proposes a circular economy framework that emphasizes waste-to-resource conversion, lifecycle extension, and reduction of virgin material consumption. By integrating multiple waste streams into construction practices, the approach not only minimizes landfill dependency but also reduces carbon emissions and promotes cost efficiency. The findings suggest that adopting such integrated circular strategies in Karachi requires coordinated policy support, technological advancement, stakeholder engagement, and increased awareness. This transition has the potential to transform the construction sector into a more sustainable and resource-efficient system while addressing the city’s growing waste management crisis.