Durability performance of binary and ternary blended cementitious systems with calcined clay: a RILEM TC 282 CCL review

The durability performance of blended cementitious systems with calcined clays is reviewed in this paper by the RILEM TC 282-CCL on calcined clays as supplementary cementititous materials (SCMs) (working group on durability). The impact of metakaolin and other calcined clays on the porosity and pore structure of cementitious systems is discussed, followed by its impact on transport properties such as moisture ingress. The durability performance of binary and ternary cementitious systems with calcined clay is then reported with respect to chloride ingress, carbonation, sulphate attack, freeze–thaw and alkali-silica reaction. The role of unique microstructural alterations in concretes with calcined clay-limestone combinations due to the formation of CO₃-AFm and their impact on different durability exposures is emphasised. While a large majority of studies agree that the chloride resistance of concretes with calcined clays is significantly improved, such concretes seem to be more susceptible to carbonation than those produced with plain Portland cement or other SCMs used at lower replacement levels. Also, several studies are focused on metakaolin and lower grade kaolinite clay, while there are limited studies on calcined smectite/illite or mixed clays, which could also play a crucial role to the improved adoption of large reserves of clay sources to produce sustainable binders.