Synergistic Role of Surface-Modified Silica Aerogel and Basalt Fibres in Structurally Reliable, Energy-Efficient Masonry Mortar

Abstract This study develops a sustainable masonry mortar incorporating a low dosage of KH-570 surface-modified silica aerogel and basalt fibre to improve thermal insulation while maintaining mechanical compliance suitable for non-load-bearing applications. This work, to the authors’ knowledge, is the first to combine KH-570 functionalised aerogel with basalt fibre to overcome the insulation–strength trade-off at low aerogel dosages. Two mortar series were prepared: (i) mortars containing 3, 5, and 7 vol. % unmodified aerogel as partial sand replacement and (ii) mortars with the same aerogel contents combined with 1 wt% cement-chopped basalt fibre. The setting time, flow of fresh mortar, dry bulk density, mechanical strength, and thermal properties were evaluated. Basalt fibre-reinforced samples demonstrated compressive strength increases of 8.0%, 7.2%, and 7.6%, and flexural strength gains of 6.0%, 8.0%, and 6.6%, respectively, compared with non-reinforced aerogel mortars while meeting the requirements of ASTM C270. Standard Specification for Mortar for Unit Masonry. ASTM International, West Conshohocken, PA, USA. (Type N), EN 998-2 (Class M5), and AS 4456.10 (Class M2). Thermal conductivity was reduced by up to 65% relative to conventional mortar, reaching its lowest value at 7 vol% treated aerogel combined with basalt fibre. The results demonstrate a material-efficient route to thermally insulating mortars that retain mechanical performance suitable for non-load-bearing masonry.