Investigation of mechanical performances of insulating building materials based on rice husk and hemp hurd

Abstract

The purpose of this paper is to investigate the mechanical properties and the lime-based binder hardening of green concretes made of rice husk or hemp hurd. Concrete specimens were subjected to different curing conditions. Under natural conditions, they were cured during 10 months in a climate-controlled room (20°C ‒ 50%RH) and exposed outdoors. The work also focused on an accelerated carbonation curing (CO2 curing) aiming to improve the short term compressive strength (1-2 months) of the concrete materials. Under natural conditions, the results indicated that the lime binder was almost strengthened in the same way for both concretes with a similar rate of carbonation. However, the rice husk concrete was characterized by a ceiling effect of the mechanical performances over time which was attributed to the lower bonding strength between rice husks and lime. Concerning specimens exposed outdoors, the strength gain over time was more significant owing to more favorable humidity conditions for carbonation. The accelerated carbonation curing led to an increase of the mechanical properties of the concretes in the short term. The compressive strength after the CO2 curing was approximately equivalent to those obtained after 10 months of outdoor exposure under natural carbonation.