Prediction model for calculation of the limestone powder concrete carbonation depth

Abstract

The efficient way to mitigate the impact of the concrete industry on climate change is to reduce the clinker content in the concrete mix. Beside incorporating supplementary cementitious materials (SCMs), it is possible to use high filler content combined with concrete mix optimisation. Limestone powder emerges as a promising filler mineral due to its availability and ready-to-use technology. In this work, the carbonation resistance of concrete with a high limestone powder content (45–65% of the powder phase) was experimentally tested. Test results showed that, with an optimized mix design featuring low water content and increased paste and plasticizer volume, concrete mixes satisfied high workability and strength demands for commonly applied strength classes. However, carbonation resistance remains a challenge. After two years in indoor natural conditions, carbonation depths were 8%, 28%, and 67% greater than referent Portland cement concrete for mixes with 47%, 58%, and 65% limestone powder content, respectively. Further analyses showed the inapplicability of the existing fib Model Code 2010 service life prediction model to limestone powder concrete. Based on a comprehensive database of experimental results, the modification of the fib prediction was proposed. A full probabilistic service life analysis revealed that for concrete with more than 20% limestone powder content and for both 50 and 100-years’ design service life, the currently prescribed concrete cover depths in European standards should be increased, depending on the carbonation exposure class.