Impact of basalt fiber on the fracture properties of recycled aggregate concrete

Abstract

This research investigates the effect of basalt fiber (BF) on the fracture properties of recycled aggregate concrete (RAC). Three-point bending tests were performed on notched beams of BF -reinforced recycled aggregate concrete (BFRAC) at varying recycled coarse aggregate (RCA) substitution rates. The study aimed to analyze the mechanisms of influence between BF volume fraction and its length-diameter ratio (l/d) in relation to BFRAC fracture attributes. Through an analysis of the load versus crack mouth opening displacement (P-CMOD) and load versus deflection (P-δ) curves, the fracture energy (GF) and the double-K fracture parameters were determined. Results showed that BF-reinforced concrete (BFRC) registered an average enhancement of 6.95% for the admixture of BF initiation fracture toughness（KICini）, with an average rise in lift of 39.10% for unstable fracture toughness（KICun），and a GF increment of 22.29%. Optimal fracture properties for BFRAC were observed in RAC with a BF l/d of 1200 and a 0.15% mixing rate, reflecting a 36.56% overall performance increase.For a 50% RCA substitution rate, the peak KICini was reached at BF l/d of 1400 with a 0.20% volume fraction. The most favorable KICun occurred with a BF l/d of 1200 and a 0.20% incorporation rate. At a 100% RCA substitution rate, the optimal GF enhancement was observed with a BF l/d of 1200 and a 0.25% addition. This study also categorizes BFRAC fiber crack propagation into three stages: crack initiation and progression, virtual crack stable development, and macroscopic crack destabilization and progression, delving into the microsystem mechanisms by which BF augments RAC's macroscopic fracture behavior.