Microstructural Characterization of Prefabricated Hempcrete Blocks

Sustainable building materials have been developed to reduce the polluting emissions and the exploitation of natural resources of the building sector. Among these materials, an outstanding category is that of nature-based solutions which are produced recovering waste or by-products of agricultural cultivations and using them as vegetal aggregates to replace the traditional ones. This paper focusses on hempcrete which is produced mixing the by-product of industrial hemp cultivation (i.e., shives) and lime to obtain a sustainable, breathable and insulating material. The strength of hempcrete develops through carbonation of the binder that, leading to the formation of calcium or magnesium carbonates and mineralization of shives, determines the microstructure and hence most of the characteristic properties of the material. The aim of this research is to investigate how carbonation influences the microstructure of hempcrete when different recipes are used for blocks production. This study consists in the characterization of the material through techniques such as XRD (X-ray Diffractometry), SEM (Scanning Electron Microscopy) and TG-DTG (thermogravimetric analyses). Moreover, the evolution of carbonation is studied analyzing samples at different maturation times. The investigation of the carbonation reaction degree is also crucial to evaluate the environmental performances of the material because it allows the quantification of the carbon dioxide uptake. Also, periodic characterization allows to assess the durability of hempcrete and to select the best formulation according to the designed application and the corresponding service conditions.