Mechanical properties and durability of hemp-lime concretes: Fid-Bau Portal

Mechanical properties and durability of hemp-lime concretes

Walker, R. / Pavia, S. / Mitchell, R.

Highlights • The effect of binder type on mechanical strength and durability is investigated. • At the hemp interface, the commercial binder has abundant hydrates while lime:pozzolan binders are mainly carbonated. • Binder hydraulicity contributes to strength development but has a lesser effect at 1 year when other factors also contribute. • Hemp concretes made with lime:pozzolan binders are more sensitive to freeze:thaw action than more hydraulic binders. • Short-term salt exposure resulted in the precipitation of salt layers but did not impact compressive strength at 1 year.

Abstract Hemp-lime concrete is a sustainable and carbon negative construction material. This paper investigates the effect of binder type on mechanical strength and durability (resistance to freeze–thaw, salt exposure and biodeterioration). It compares hemp-lime concretes made with a hydrated lime and pozzolan binder to those including hydraulic lime and cement. SEM analysis revealed abundant hydrates at the hemp interface of the strongly hydraulic commercial binder while the lime:pozzolan binders were mostly carbonated. Increasing binder hydraulicity enhances early strength development however, all concretes achieved similar compressive strengths at 1year irrespective of the binder type. The concretes with lime:pozzolan binders are more sensitive to freeze:thaw action than those with more hydraulic binders. Salt exposure resulted in the precipitation of salt layers in the concrete however, this did not have a detrimental impact on the compressive strength of the concrete at 1year. The results evidenced that hemp concrete is resistant to biodeterioration (7month exposure). Finally, the addition of water retainer improved the early strength development and freeze:thaw resistance of the concrete with lime–pozzolan binder.