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A framework is proposed, along with two objective indices, for the selection of concrete mixture proportions based on sustainability criteria. The indices combine energy demand and long-term strength as energy intensity, and carbon emissions and durability parameters as A-indices, which represent the apathy toward these essential features of sustainability. The decision support framework is demonstrated by considering a set of 30 concretes with different binders, including ordinary portland cement (OPC), fly ash, slag and limestone calcined clay cement (LC3). In addition to the experimental data on compressive strength, chloride diffusion and carbonation, life cycle assessment has been performed for the concretes considering typical situations in South India. The most sustainable of the concretes studied here, for service life limited by chloride ingress, are those with LC3, OPC replaced by 50% slag, and ternary blends with 20% each of slag and fly ash. In the case of applications where carbonation is critical, the appropriate concretes are those with OPC replaced by 15-30% slag or 15% fly ash, or with ternary blends having 20% slag and 20% Class F fly ash.

Considering that India is the second largest producer and consumer of cement in the world, it is understood that its production and use has a tremendous impact on the energy consumption and carbon dioxide emissions. More than 75% of cement in India is made by blending ground clinker with fly ash, ground granulated blast furnace slag, limestone or other supplementary cementitious materials (SCMs). Further, there have been only limited studies on the sustainability assessment of cement and concrete that can give a clear picture of the impact and help mitigate it in future. The work presented here is based on realistic process maps made in cement plants and data collected from them. The concretes assessed are based on two typical strength grades obtained with blended cements, as well as only portland cement. The results highlight the importance of the SCMs in terms of total energy consumption and carbon dioxide emissions. The study also draws attention to the need to use high grades of concrete to better harness the benefits of the SCMs. Further, the need to generate more relevant data sets for the Indian context is recognized.