Comparative analysis and modification of evaluation methods for the pozzolanic reactivity of natural volcanic powders

Rapid and accurate assessment of the pozzolanic reactivity of natural volcanic powders (NVPs) is crucial for their practical application in cement-based materials. In this paper, six conventional pozzolanic reactivity evaluation methods were carried out on three collected NVPs. It was found that various evaluation methods give different ranking of the pozzolanic reactivity of the tested materials, owing to the changes in the test conditions. In addition, based on the R3 pozzolanic reactivity test method standardized in ASTM C1897-20, a modified R3 method by adjusting the usage of sulfate and alkali was proposed. Analysis of hydration products confirmed that the proposed modified R3 method can effectively simulate the interstitial solution of the NVPs-cement composite system within 24 h, and the accuracy of pozzolanic reactivity evaluation of NVPs with low reactivity was greatly improved.