Sustainable Recycled Aggregate Concrete Incorporating Volcanic Ash and Basalt Fibers with Enhanced Mechanical, Durability, and Environmental Performance

Abstract

This study evaluates the mechanical, durability, statistical, and environmental performance of recycled aggregate concrete (RAC) incorporating volcanic ash (VA) as a partial cement replacement and basalt (BA) fibers as reinforcement. VA was used at 5%, 10%, and 15%, followed by BA fiber additions of 0.25%, 0.50%, and 1% by volume. Fresh density, water absorption (WA), rapid chloride permeability (RCPT), compressive strength (CS), flexural strength (FS), and life-cycle environmental impacts were systematically assessed, and regression analyses were conducted to quantify relationships among parameters. Replacing cement with 10% VA reduced WA from 8.78% to 8.21% (6.49% reduction) and RCPT from 3917 to 3712 coulombs (5.23% reduction), indicating improved pore refinement and chloride resistance. A strong correlation between WA and RCPT (R2 = 0.849) confirmed that ion permeability is primarily governed by capillary porosity. Moderate negative correlations were observed between durability parameters and CS, with R2 values of 0.592 (WA–CS) and 0.682 (RCPT–CS). The highest CS (38.64 MPa) was achieved with 10% VA and 0.25% BA fibers, representing a 3.79% increase over the control. Increasing fiber content to 1% reduced CS by 10.98%. FS exhibited only minor variations, with a maximum increase of 2.55% compared to the control mixture, but showed stronger correlations with durability indicators (R2 = 0.776 for WA–FS and R2 = 0.676 for RCPT–FS) than with CS (R2 = 0.592). Life cycle assessment (LCA) revealed a 10.46% reduction in global warming potential (GWP) at 10% VA. Overall, 10% VA with 0.25% BA fibers provides the most balanced performance.