Bio-fibre earth composite mortar: A structural and hygrothermal assessment

Abstract

Bio-fibres and earth as a building material have been used for thousands of years and can be utilised due to their relative abundancy around the globe. The aim of this work is to combine these materials in order to give potential for a new, sustainably sourced, non-load bearing hygric buffering panel for indoor thermal management with bio-fibres commercialised in UK. Currently, there is limited knowledge specifically as to how bio-fibres and earth combine in order to enhance their inherent characteristics. This uses two differing mix designs and 3 differing bio-fibres (Wool 1, Wool 2 and Saw Mill Residue). Earth was utilised by using locally sourced material from Liverpool (NW England). Prismatic, 0.1m2 x 0.1m2 and 40mm disc samples were cast and samples were exposed to cyclical step changes in relative humidity at 75% for 8 hours and 53% for 16 hours at 23°C, in order to mimic a UK household occupancy. Results demonstrate that an optimised mix lead to at least 30% improvement of properties if Saw Mill Residue (SMR) is added. In comparison to a plain earth mortar, the addition of SMR reduces density, porosity and increases moisture buffering.