Development of a new rapid, relevant and reliable (R³) testing method to evaluate the pozzolanic reactivity of calcined clays

This paper introduces a new rapid, relevant and reliable (R³) test to characterize the pozzolanic reactivity of calcined clays. This test uses isothermal calorimetry to evaluate the reactivity by monitoring the heat release in portlandite/ calcined clay/limestone model systems. Once the mix design was adjusted, a wide range of calcined clays was investigated. Tests were first run at 20 °C. Good correlations were found between the heat release at 6 days and the compressive strength results on mortar blends containing calcined clays and limestone. Another series of tests were carried out at 40 °C, enabling the isothermal calorimetry test duration to be reduced from 6 to 1 day, while keeping good correlations with strength results.