ECO2 framework assessment of limestone powder concrete slabs and columns

Producing limestone powder requires comparably far less energy than the production of ordinary Portland cement (OPC), making it a promising sustainable solution for partial replacement of OPC in concrete. Lower production energy could be translated into lower environmental impact and lower cost, which are two pillars of the sustainability of the resulting concrete. However, the question remains if replacing OPC with larger percentages of limestone powder would compromise the performance of the resulting concrete to a level that surpasses the environmental and economic gains. In order to assess the collective impact of these concretes, a performance-based multi-criteria decision analysis framework, ECO2, is used. For that purpose, 26 experimentally verified, concrete mixtures with and without limestone powder were evaluated through potential application in two types of reinforced concrete (RC) structural elements (slabs and columns) under identical environmental condition. The main results of the research showed a clear environmental advantage of concrete with a reduced OPC content, but the relatively higher super-plasticizer amount in some cases could affect the final sustainability performance of the resulting mix. In the case of RC slabs, the best ECO2 score was obtained for concrete containing limestone powder. Mixtures with 200-250 kg of cement per unit volume of concrete had the highest ECO2 score for all the considered criteria. In the second case, due to the nature of the structural performance requirements in columns, the crucial influence of the concrete compressive strength is clear. The obtained results have shown approximately equal sustainability potential of OPC and limestone concretes in vertical elements such as columns. However, it seems that a certain improvement in the design of concrete mixtures with a high limestone powder content could make these competitive in all fields.