AbstractIn recent years, there has been increasing interest in using cementitious materials as a catalyst-supporting media such as air-purifying paving block, self-cleaning exterior wall, and photocatalytic ceiling panel. Despite many works on photocatalytic cementitious materials, most of them were focused on the application of TiO2-based cement mortars. Little work has been done on the development of photocatalytic functionalities on highperformance fiber-reinforced cementitious composite (HPFRC). Engineered cementitious composites (ECCs), a class of HPFRC, have been used in a wide range of full-scale applications, from sprayed ECC for dam retrofitting to lightweight building facade and bridge deck pavement. In this work, titanium dioxide (TiO2) was incorporated into lightweight ECC. The influence of TiO2 and different lightweight ingredient materials on mechanical properties and antibacterial behavior based on Escherichia coli (E. coli) was investigated. Two types of lightweight aggregates were evaluated: fly ash cenospheres (FACs) and glass bubbles K-1. Furthermore, an air-entraining agent (AEA) was also evaluated to induce air bubbles to achieve lightweight ECC. The use of a glass bubble is preferable to achieve lightweight ECC with a density of around 890 kg/m3 (60% lower than normal ECC) while maintaining a tensile strain capacity of more than 3% with moderate tensile strength. At the same time, lightweight ECC using glass bubbles show the smallest number of viable bacteria after 240 min of ultraviolet (UV)/visible light exposure. The smallest number of viable bacteria indicates it has the highest antibacterial activity among lightweight ECC materials. The use of glass bubble significantly alters the pore structure of lightweight ECC, which improves the access to irradiate TiO2 particle. The incident photon could pass along the pore to activate more TiO2 particles for the photocatalytic process.