Fire behaviour of hemp, clay and gypsum-based light biobased concretes and renders

Greenhouse gas emissions from cement manufacturing account for about 8 to 10 percent of total CO2 emissions worldwide. To reduce these emissions, researchers are developing new concrete manufacturing techniques and processes to reduce high energy consumption and environmental impacts. Biobased concretes are eco-friendly insulating materials for building industry that can respond to this problem. However, there is a lack of knowledge regarding how these plant-based fillers ignite and contribute to heat release in case of fire. In this work, the fire behaviour of a series of hemp-based earth and/or gypsum concretes covering a large range of densities (180–1500 kg/m3) is investigated using the cone calorimeter at an incident heat flux of 50 kW/m2. The fire performances are mainly monitored by the thermal inertia of the materials. Only the lightest concretes ignite with a density threshold for ignition occurrence around 500 kg/m3. For a density of 261 kg/m3, the critical heat flux of an earth-hemp concrete was found to be close to 27 kW/m2. The flaming period remains very short in all cases.