The long-term integrity of structures is a key concern in civil engineering, and the use of pozzolanic materials offers a pathway to improved durability while supporting more sustainable cement production. Bamboo leaf ash (BLA) has emerged as a promising supplementary cementitious material and a potential alternative to conventional cement. This study evaluated cement paste and mortar mixtures incorporating 20%, 25%, 30%, and 40% BLA as partial replacements for cement. We used thermogravimetric analysis to investigate the formation of hydrated products, and assessed the physical and durability-related properties of mortars, including compressive strength, electrical resistivity, and porosity. Composite durability produced with BLA was further assessed through carbonation, chloride migration, and chloride diffusion tests. The results indicated that BLA-generated composites exhibited reduced porosity and compressive strength comparable to the reference mortar across all replacement levels. In addition, durability tests demonstrated enhanced resistance to chloride-ion penetration, underscoring the potential of BLA as an eco-friendly pozzolanic material for partial replacement of cement.