Formulation d’un liant pouzzolanique pour la confection d’un béton végétal hygroscopique

Abstract

Climate change is driving the need to rethink the way buildings are constructed to limit greenhouse gas (GHG) emissions. A building emits GHGs from the extraction of materials, during its operation and until its disposal at the end of its life. The use of petrochemicals and mineral-based insulation materials goes against the societal duty to reduce GHGs. A material with great potential is the hemp concrete composed of a lime-based binder, hemp hurd and water. Hemp is a plant that can be harvested during each growing season. It can quickly sequester carbon dioxide (CO2), a GHG, up to four times more than a tree according to studies. In addition, hemp concrete can regulate humidity and temperature in a natural way in a building through the absorption capacity of hemp concrete, thus bringing comfort to the residents. Hemp concrete is a good thermal insulator, recyclable, non-flammable, natural pest repellent and protects against wood mould. There are currently two Quebec companies that specialize in the construction of turnkey hemp concrete homes. However, the construction methods remain artisanal and require a lot of labor. The importation of formulated binders or natural hydraulic lime marketed in Europe makes hemp plant-based concrete material inaccessible and unviable for the North American market. The objective of the proposed research is to study the possibility of formulating a binder adapted to vegetal hemp concrete using materials available in North America, while limiting the addition of hydraulic binder, which is a major GHG emitter. The work focuses on optimizing the curing process using theoretical approaches from the literature by studying the hydrated phases produced in the pozzolanic binder formulated as well as optimizing the proportions of the constituents to meet the various research hypotheses. A critical look at the optimization of the formulated binder will be taken on the impact of the binder on the hygroscopic character of moisture regulation of the final composite material. The results obtained from the optimization of the binder will promote the use of a pozzolanic binder based on lime and metakaolin in binary formula. Despite the results obtained supporting the idea of a larger capillary volume of connected pores for a pure ternary pozzolanic binder formulated with a higher SiO2/Al2O3 (Si/Al) mass ratio, the hygroscopic properties of moisture regulating plant-based concretes do not appear to be dependent on this binder design parameter. Despite the variability in the proportions of the binder formulation, the hemp hurd seems to be the dominant element of the hygroscopic characteristics of the material according to the proposed approach. Therefore, the outcome of this research allows a better acceptance of the use of a binary lime-metakaolin formulation for the elaboration of hemp plant-based concretes. The proposed binary formulation will benefit placement through greater initial cohesion of the material.

Date	8 Sept 2022
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Daniel Perraton (Supervisor) & Claudiane Ouellet-Plamondon (Co-supervisor)