Rice husk-earth based composites: A novel bio-based panel for buildings refurbishment.

• Bio-based composites based on rice husk (RH) and an earthen matrix are evaluated. • RH content improves thermal conductivity and contribute to hygrothermal comfort. • RH increase at least 20% the composites MBV and their ability to adsorb-desorb indoor moisture. • Pre-boiling of RH reduces biological susceptibility and improves mechanical behaviour. • Optimised composite panels can be applied in coatings systems of massive walls and ceilings. With the aim of developing economic and ecological bio-based composite panels to be used on indoor wall or ceiling coating systems, contributing to hygrothermal comfort and health, three different composite formulations were produced, differing on the content and pre-treatment of rice husk: 15% and 30%, only dried or previously boiled. Composite samples were tested for biological development and several physic-mechanical characteristics. Increasing on rice husk content decreases thermal conductivity due to bulk density decrease, decreasing ultrasound velocity, flexural strength, abrasion and fire resistance, but improving the moisture buffering capacity at least in 20%. For high rice husk-content composites, its pre-boiling decreases biological susceptibility although decreasing resistance to fire, most probably due to destruction of the cellulose wall, but significantly increases abrasion resistance and compressive strength, probably because of a better bond between the rice husk and the earthen matrix, quicker reaching a high water vapour adsorption limit. [ABSTRACT FROM AUTHOR]