UR2: Ultra-rapid reactivity test for real-time, low-cost quality control of calcined clays
Yujia Min, Hossein Kabir, Chirayu Kothari, Mohammad Iqbal, Nishant Garg
Abstract
To reduce cement's carbon footprint, there is growing interest in commercial adoption of sustainable SCMs such as calcined clays. However, the existing ASTM standard (R 3 test, C1897) to test the reactivity of such clays takes up to 7 days and cannot be used for real-time quality control in an industrial setting. We address this issue by introducing a 5-min Ultra-Rapid Reactivity (UR 2 ) test. By dissolving 47 clay specimens in 4 M NaOH solutions at 90 °C, we report that a dissolution index of 1.54Al + Si correlates strongly to the 7-day R 3 heat (R 2 = 0.92, RMSE = 94.1 J/g). This dissolution index also correlates to the 28-day compressive strength for 14 clay mixtures (R 2 = 0.94, RMSE = 1.7 MPa). This UR 2 test relies on colorimetry and can be conducted via off-the-shelf, low-cost cameras. Overall, our new UR 2 test opens a pathway for real-time, low-cost quality control of calcined clays. • An Ultra-Rapid Reactivity (UR 2 ) test predicts 7-day R 3 results in mere 5 min. • Al and Si dissolved from calcined clay are combined using an index of 1.54Al + Si. • For 47 clay specimens, this dissolution index correlates to the R 3 heat (R 2 = 0.92). • Al and Si can be measured via colorimetry using off-the-shelf, low-cost cameras. • This test opens a pathway for real-time, low-cost quality control of calcined clays.