Recycled Coarse Aggregates in Concrete: A Comprehensive Study of Mechanical and Microstructural Properties

Abstract

Addressing the increasing demand for concrete due to advancements in the construction sector and population growth, this research explores the critical intersection of waste management and sustainable construction practices. By incorporating recycled coarse aggregate (RCA) derived from construction and demolition waste into concrete, waste reduction and natural resource conservation is achieved. An innovative standard compaction method is utilized to investigate the complex dynamics of RCA's influence on concrete properties. Key parameters examined include workability, compressive strength, flexural strength, split tensile strength, microstructural characteristics (XRD, SEM, EDAX), and modulus of elasticity. A distinctive feature of this research involves systematically replacing conventional coarse aggregates with RCA at varying proportions: 0, 25, 50, 75, and 100%. The comprehensive analysis reveals significant improvements in the fresh, hardened, and microstructural properties of concrete. Results indicate a nuanced relationship between RCA replacement levels and concrete strength, with the optimal mixture at 25% RCA replacement (RCA 25) demonstrating notably higher compressive (11.56%), flexural (3.06%), and split tensile (5.17%) strengths compared to the control concrete. Additionally, RCA 25 exhibits an 8.91% increase in modulus of elasticity. XRD, SEM, and EDAX analyses provide insights into the underlying mechanisms, indicating that pozzolanic activity enhances strength at lower RCA replacement levels by producing more hydration products, while strength may decrease at higher replacement levels. The significance of this research lies in its novel methodology, addressing a critical gap in understanding the intricate relationships between RCA content and concrete performance. The findings strongly advocate for the judicious use of recycled materials in concrete, contributing to environmental conservation and the long-term resilience of construction materials.