Physical-mechanical and durability properties of alkali-activated mortar with natural fibres

In this work, the behaviour of sustainable composite materials prepared with a metakaolin-based alkali-activated matrix and natural fibres was thoroughly investigated. Short hemp fibres (approximately 3 mm in length) were randomly dispersed at up to 3 wt% of the metakaolin amount. The physical, mechanical, and durability properties of the resulting alkali-activated mortar were evaluated and compared with reference samples without fibres. The results showed an increase in flexural strength and toughness with the addition of fibres, while water permeability decreased with the fibre incorporation. Finally, specimens subjected to freeze-thaw (-18°C and +20°C) and thermo-hygrometric ((1) 12 hours at 10°C and 95% R.U., (2) 12 hours at 45°C and 30% R.U.) cycles performed in a climatic chamber showed improved durability when fibres were present in the mixes.