Incorporating environmental evaluation and thermal properties of concrete mix designs

One of the main challenges in sustainable design of buildings is to improve the energy efficiency of the building during its lifetime along with reducing the environmental impact of the design. Recent advances in concrete technology offer lower embodied emission through the application of supplementary cementitious materials and recycled aggregates. There are also improvements to thermal properties with the application of admixtures. However, the relationships between the environmental impact (Cradle to Gate) and thermal performance of concrete mix designs have not been researched adequately. The Green House Gas (GHG) emissions associated with each individual concrete component and its production need to be considered with greater refinement. This study correlates the impacts of selecting a concrete mix design in terms of CO2-e with resulting thermal conductivity and density at the design stage of buildings. This paper examines 90 concrete mix designs from published literature to identify their embodied emissions and thermal conductivity in order to discuss the relationship between low embodied carbon dioxide equivalents (CO2-e) emission alternatives and thermal conductivity. The embodied CO2-e of a variety concrete mix designs were quantified by compiling embodied CO2-e coefficient for each individual component in the concrete. The results show the variation in embodied CO2-e and thermal conductivity of concrete mixes. The application of readily available supplementary cementitious material can reduce embodied CO2-e (kg CO2-e) by up to 16% in comparison with general practice. Furthermore, the thermal conductivity of concrete mix is influenced by changing the density of aggregates and the proportion of cementitious materials. In completing this work the results obtained from the study are compared with six different inventory databases: ICE (Hammond et al., 2011), Crawford (2011), Alcon (2003), eTool (2014), BPIC (2014) and AusLCI (2013). The comparison identifies some inconsistencies in calculation of embodied CO2-e across the different databases. This is attributed to variation in embodied CO2-e coefficients and lack of in-depth consideration of the detailed properties of each individual concrete mix design