Long‐term performance of recycled aggregate concrete incorporating natural zeolite

Abstract This study investigates the long‐term mechanical, microstructural, and environmental performance of recycled aggregate concrete (RAC) incorporating natural zeolite (NZ) and silica fume (SF) as supplementary cementitious materials (SCMs). By partially replacing cement with 8% SF or 15% NZ and substituting natural aggregates with 30%, 50%, and 100% recycled concrete aggregates (RCA), the research aims to enhance concrete sustainability while addressing long‐term performance concerns associated with RCA. A comprehensive experimental program was conducted over a 3‐year curing period, including compressive and splitting tensile strength testing, water penetration analysis, pore structure evaluation (via MIP), microstructural analysis (via SEM) and life cycle assessment (LCA). Incorporating RCA consistently reduced compressive strength due to increased porosity and micro cracking in the adhered mortar and interfacial transition zones (ITZ). However, internal curing effects from higher RCA content partially offset early‐age strength losses and enhanced long‐term hydration. Both NZ and SF improved early‐age mechanical performance and refined the pore structure, with SF being more effective in reducing water permeability and pore sizes. NZ showed moderate long‐term benefits, particularly in tensile strength and matrix densification, attributed to its internal curing capacity. Despite improvements in microstructure, the 3‐year compressive strength of SCM‐modified mixes remained comparable to or slightly below that of the control mix. LCA results revealed reduced climate‐related impacts from partial cement replacement, although 100% RCA increased overall environmental burdens. These findings highlight a strong understanding of the role of NZ and SF regarding the long‐term performance, durability, and sustainability in RAC—particularly when internal curing and microstructural development are carefully considered in the mix design—and underscore the capacity of RCA to provide internal curing in long‐term conditions, which can help compensate for strength losses.