Enhancement of lime-hemp concrete properties using different manufacturing technologies
The EU directive 2010/31/EU – sets goals to reduce CO2 emission levels by 20% until year 2020. As primary energy for households and construction industry both are among the largest manufacturers of CO2, a building material that can positively impact both these industries is topical. A lime-hemp concrete (LHC) is a material with negative CO2 balance, but to achieve the goals set in EU directive a more industrialized product, that can also be used in insulation of existing buildings is needed, so methods of LHC slab and block manufacture are tested in this paper. Eight different types of hemp shives are taken and twelve LHC mixes are prepared to assess the importance of hemp granulometrical distribution. To measure the effect of different preparation techniques mixes in two different mixers – gravity and forced action – were prepared to test the superiority of the latter as it is widely used in LHC production. Also different drying methods – natural, forced with temperature at various stages and with increased moisture – were tested. As well as various hydraulic additives were tried in order to increase the mechanical properties of the LHC. After complete drying, physical and mechanical properties - density, thermal conductivity, compressive and flexural strength - were determined and compared to assess the most suitable materials and manufacture technologies for LHC blocks. Also a reaction to fire test were performed for one of the samples. The results allow to better understand the principles of how the material works and how it`s properties can be enhanced with various manufacture techniques. The results suggest that LHC blocks have the necessary properties and potential to become widely used in improvement of thermal insulation of existing buildings.