Addressing key challenges in MK-PLC blends at early ages: Workability, slump retention, and heat of hydration

Abstract

Toward broadening utilization of higher fractions (i.e., >10% by mass) of metakaolin (MK) in concrete construction, several key technical challenges remain. Among these are those associated with differences in early age properties deriving from greater MK additions; these include reduced workability, more rapid slump loss, and increased heat of hydration compared to traditional concrete. Due to competing dilution and acceleration effects associated with the introduction of finely divided limestone (and potentially more fine cement), these effects can be potentially exacerbated or ameliorated when MK is combined with Portland-limestone cement (PLC). This paper examines each of these challenges and offers solutions, in the form of recommended admixtures to improve workability and slump retention and refined heat of hydration models which consider the contributions of MK.