Buildings are responsible for approximately 40% of the global energy consumption and CO2 emissions. These values include the operational energy (OE) and operational carbon (OC) required for heating, cooling, etc., but they are even greater if the embodied energy (EE) and embodied carbon (EC) are also included, i.e., the energy and CO2 emissions involved in the production process. One innovative development of sustainable building materials that was proven to be energy efficient and environment friendly is Lime-Hemp Concrete (LHC) which is based on hemp bio-aggregate and lime. However, lime, like other fired materials, has relatively high EE and EC values. Few works show the high potential of clay (unfired) as an alternative binder for LHC.
The current research studied the influence of replacing the lime in LHC with alternative unfired binders in several contents. Five alternative binders with low EE and EC values were examined (based on clay, limestone, dolomite, and basalt), including waste by-products of aggregate quarries, these last ones presenting additional environmental benefits. The thermal conductivity and heat capacity (thermal mass) were investigated, aiming to obtain a good balance between thermal insulation and heat capacity, in order to improve the thermal behavior of the building and reduce its OE and OC. The thermal, physical, chemical and mechanical properties were also examined. The four mixtures that presented the most attractive results were selected for the next stage which examined the thermal behavior of test cells composed from those mixtures and compared it to conventional building materials. Based on the results of the test cells, the OE and OC were calculated by EnergyPlus simulation. Eventually, Life Cycle Analysis (LCA) was conducted in order to assess the energy and CO2 savings ensuant to replacing the lime in LHC with alternative binders at several contents, compared to conventional building materials.