Mechanical and hygrothermal properties of hemp-silica bio-composites

Abstract

This research investigated the development of a fast-drying silica-based binder for hemp concrete products with enhanced mechanical and thermal properties. Hemp-silica bio-composites were prepared by mixing hemp shivs with a two-component binder system composed of liquid sodium silicate and tributyl citrate (TBC). Compressive strength, thermal conductivity, moisture buffering value, cyclic moisture resistance and microstructure of hemp-silica composites were analysed, and the results were compared with those of hemp-lime concrete. Hemp-silica blocks with shiv-liquid sodium silicate mass ratio of 1:3.75 and TBC content of 37.5 wt% of sodium silicate dry matter produced a compressive strength of 0.56 MPa only after 3 days of drying and 1.92 MPa after 28 days. These were higher than hemp-lime blocks at the same density range. Hemp-silica panels showed a thermal conductivity of 0.101 W/mK and an excellent moisture buffering value of 3.49. Hemp silica formed an open porosity with large air gaps between the particles and a water-resistance silica-based layer on the shiv surface producing a higher moisture resistance compared to hemp-lime systems. This paper focuses on the development of a novel fast-drying binder system with a potential for use in conjunction with other lingnocellular plant aggregates to form low-carbon and efficient multifunctional building materials.