Study of two concrete mix-design strategies to reach carbon mitigation objectives

The building and construction sector is a major CO2 producer and climate change perspectives urged to reduce CO2 emissions. The impact of concrete buildings on environment is mainly due to clinker, which is the main material used all over the world to produce cement and which releases a bit less than 1 ton of CO2 per ton of clinker produced.In this study, we first evaluate if the medium term CO2 emission reduction objectives for the cement industry are realistic according to our current scientific and technologic knowledge. We consider two environmental strategies. The first one is the substitution of clinker by mineral additions in cement in order to reduce the environmental cost of the material for a given volume of material; the second one is the reduction of the concrete volume needed for a given construction process by enhancing the concrete performances. The impact on CO2 emissions of a combination of these options is also roughly evaluated. We show that medium term objectives can be reached although long term objectives will need further research developments. We moreover present here a first step towards mix-design methods associating environmental costs and performance requirements which could allow for a better balance between societal demand in terms of environment and technical building requirements.