Effect of pore structure on the performance of photocatalytic lightweight lime-based finishing mortar

•Photocatalytic lightweight indoor hydraulic lime-based finishing mortar is designed.•Effect of expanded glass and expanded silicate on photocatalytic activity is assessed.•Effect of pore structure of lightweight mortar on photocatalytic activity is studied.•Drying shrinkage and water absorption of the lightweight finishing mortar are studied.•Thermal properties of the lightweight finishing mortar are studied. The present paper aims to evaluate the performance of photocatalytic lightweight indoor hydraulic lime-based finishing mortars, with Portland cement-based finishing mortar as a reference. Two different types of aggregates, expanded glass and expanded silicate, are utilized to achieve the lightweight character and their contributions are investigated. The pore structure of the developed mortars is determined by mercury intrusion porosimetry (MIP) and BET methods. The mechanical strength, drying shrinkage, thermal physical properties and air pollutant removal ability of the mortars are investigated and the effects of pore structure on these properties are evaluated. Due to the higher porosity, lime-based finishing mortars possess a higher capillary water absorption and higher drying shrinkage, which can be explained by the Kelvin-Laplace mechanism. The lime-based mortar shows very good thermal properties, with a thermal conductivity of 0.15 W/(m·K). The lime-based mortar shows a better ability of removing air pollutants, up to 46% under indoor air conditions laboratory test, compared to the cement-based mortar, which is attributed to the lower content of gel pores present in the lime-based mortar. Expanded glass shows positive influences concerning thermal properties and air pollutant removal ability compared to expanded silicate.