Enhancing Physical and Mechanical Properties of Recycled Concrete Aggregates Solid Masonry Blocks Using Fly Ash as Filler

Abstract

The escalating demand for global infrastructure has intensified the depletion of natural resources and exacerbated environmental issues, particularly those associated with the disposal of fly ash (FA) from coal-based power plants and construction and demolition (C&D) waste from ageing structures. This study investigates the sustainable utilization of these waste materials by incorporating FA and 100% recycled concrete aggregates (RCA) in the production of solid masonry blocks (SMB). Specifically, FA is used as a filler material to replace 30% of fine recycled concrete aggregates (FRCA), and its effect on the physical and mechanical characteristics of SMB is evaluated across three different cement-to-aggregate (C:A) ratios ranging from 1:18F to 1:24F. The performance parameters examined include hardened density, compressive strength, flexural strength, and water absorption. The results reveal that replacing 30% of FRCA with FA enhances mechanical strength, increases density, and reduces water absorption compared to SMB made solely with RCA. Moreover, all SMB incorporating FA met the specifications outlined by Indian standards, confirming their structural reliability. The findings affirm that FA acts as a functional micro-scale filler, promoting improved particle packing and more efficient stress transfer in SMB produced from RCA. Rather than being limited to traditional cement substitution approaches, the present study provides new experimental insights into the performance-oriented contribution of FA in masonry systems. By integrating fundamental filler mechanisms with practical block manufacturing, the findings advance the state of the art in sustainable cementitious materials and support the development of structurally sound, environmentally responsible masonry blocks.