Recycling of raw wheat husk to manufacture magnesia cement based lightweight building materials
In the last decades, the attention towards “carbon neutral” cement and agro-resources’ by-products as new alternative raw building materials has grown exponentially. Within this context, the present study deals with the design of a lightweight insulating concrete based on raw wheat husk incorporated in a highly porous magnesia cement.
Concretes made from plant aggregates are commonly formulated with lime binders, with one of these materials being lime-hemp concrete. In this work, the possibility of substituting the traditionally employed calcic lime binder with an alternative magnesium binder was explored. In the majority of the research studies, the lignocellulosic particles associated with a mineral binder come from plant stems, as is the case of hemp hurds. Wheat husks, instead, are the main by-product of the industrial process for separating the grain kernel from the inedible hull of hulled wheat species, so that their use could significantly enhance their valorisation and meet zero-waste concept. Having examined physical and structural characteristics of these lightweight aggregates, specimens made out of wheat husk and both traditional lime binder (LWC) and alternative magnesium one (MWC) were manufactured. Both thermal and mechanical properties of the ﬁnal concrete materials were studied and the results were compared to those obtained for hemp hurd concretes (LHC and MHC) manufactured with the same process.
The first results obtained for specimens cured for 10 days at 20°C and 50%RH, show higher apparent density for wheat husk concrete with an average compressive strength of 1.88±0.09 MPa in case of specimens made by alternative magnesium binder (MWC) and 0.16±0.03 MPa considering LWC. Thermal conductivity is 0.142±0.006 W/mK for LWC and 0.35±0.03 W/mK for MWC. Considering a suitable balance between thermal and mechanical properties, the use of wheat husks could be promising for the manufacture of new environment-friendly products as inner partition walls and thermal insulating components.