Standardisation of low clinker cements containing calcined clay and limestone: a review by RILEM TC-282 CCL

Materials used in concrete construction are highly regulated through national standards that set minimum material reactivity, composition, and performance. Advances have shown that the combination of calcined clay and limestone fines in cementitious systems can have a synergistic reaction that allows for high levels of clinker replacement while maintaining adequate mechanical properties and durability. Recent modifications to national standards and codes have been made to allow for the use of calcined clay and limestone fines in concrete, albeit with some restrictions on use. Building codes also impose limits such as maximum water-to-cement/binder)-ratio, minimum strength, and minimum cement content as means to meet design service life requirements in lieu of measuring durability properties. This paper reviews the major standards and codes related to calcined clay materials and their use in concrete and suggests changes that could increase adoption and clinker replacement. It is hoped that this review will provide insights that can help facilitate the wider adoption of these materials in the construction industry as well as to identify potential changes in standards or creation of new ones which might be needed to enable the rapid widespread uptake of this promising technology.