Durability Controlled Hydration Mechanisms of High-Volume FABA-Based Binders with Nano Silica and Silica Fume Modification

Abstract

High-volume supplementary cementitious materials (SCMs) offer significant potential for reducing clinker consumption and CO2 emissions, but maintaining hydration efficiency and long-term durability remains a major challenge. This study investigated the hydration behavior, microstructural evolution, and transport-related durability of high-volume fly ash–bottom ash (FABA) binders incorporating mechanically activated bottom ash, nano-silica, and silica fume. The binder systems were evaluated using mechanical, transport, and integrated microstructural characterization. The 60% FABA (M1) binder exhibited the optimum performance, achieving a compressive strength of 44.5 MPa at 56 days together with the lowest sorptivity and water absorption. Integrated SEM, XRD, TGA/DTG, and BET/BJH analyses confirmed enhanced secondary hydration, progressive matrix densification, and mesopore refinement, with the highest specific surface area (11.9 m2/g) and the smallest average pore diameter (12.6 nm). These findings demonstrate that the durability of high-volume FABA binders is governed primarily by hydration-induced pore refinement and reduced pore connectivity, providing a scientific basis for the design of durable low-carbon cementitious binders with high clinker replacement.