Quality assessment & monitoring of recycled coarse aggregates

This doctoral dissertation explores the development and application of innovative technologies designed to improve the sustainability of the construction industry by effectively using recycled coarse aggregates (RCA). The primary aim of this research is to develop, implement, and validate novel methods that incorporate advanced technologies for accurate grading and quality assurance of RCA. By enhancing the efficiency of RCA repurposing, this work seeks to broaden its use in construction projects, significantly contributing to environmental sustainability.

The research begins by introducing a novel mobile system specifically designed to conduct on-site quality inspections of unscreened RCA streams. This technology provides an easily
transportable and efficient solution to assess and categorize RCA on-site, facilitating its immediate and effective reuse in various construction applications. This system leverages advanced technologies from the field of raw materials sorting and real-time data processing to ensure the quality and usability of recycled materials, aiming to reduce construction waste and enhance material lifecycle management.

The study further investigates the integration of RCA in the production of high-performance concrete through the industrial-scale implementation of intelligent optimal grading techniques. These techniques detail the integration of optimized grading algorithms that adjust the composition of RCA to enhance the mechanical properties of concrete. This methodology not only improves the quality of final concrete but also demonstrates the practical and scalable use of RCA in demanding construction environments.

A significant portion of the research is dedicated to the characterization of RCA using Laser-Induced Breakdown Spectroscopy (LIBS). This technique offers a quick and non-destructive way to accurately identify and classify materials and contaminants for in-line quality inspection of RCA. The precision and accuracy of LIBS allow for a detailed assessment of the RCA quality, crucial for ensuring the structural integrity and longevity of RCA-based concrete structures.

Further advancements are achieved by integrating LIBS with 3D scanning technologies. This combination establishes a more precise quality control system for RCA streams. By enhancing the detection and quantification of undesirable contaminants within RCA streams, this approach ensures that the materials in the final recycled products meet the required standards, thereby improving the overall reliability of RCA. This not only maintains but also improves the structural quality of the final concrete.

The dissertation concludes by synthesizing the technological innovations and research findings, emphasizing their implications for both the scientific community and the construction industry at large. It highlights the environmental benefits of adopting RCA, including reduced reliance on virgin materials and enhancing the sustainability of construction practices. Additionally, it outlines a series of future research directions that focus on refining these technologies, exploring their economic impacts and commercial viability, and evaluating the long-term performance of structures built with RCA concrete.

Overall, this thesis provides a substantial contribution to the field of sustainable construction, offering practical, technology-driven solutions that pave the way for a more sustainable and environmentally conscious construction industry. The methodologies developed herein not only push the boundaries of academic research but also present viable, industry-ready applications that can significantly impact the way construction materials are recycled and utilized.