The cement industry is working to reduce its environmental impact by replacing clinker with supplementary cementitious materials (SCMs), including pozzolanic materials. This study examines three types of pozzolanic materials: calcined Spanish clays, natural pozzolans, and fly ash. Fifteen materials were analyzed for their kaolinite and amorphous content.
We evaluated the pozzolanic activity of these SCMs using the R³ test (measuring heat released and combined water) and the Strength Activity Index (SAI). The R³ test effectively determined pozzolanicity, showing a strong correlation with kaolinite and amorphous content. However, absolute values of heat and combined water varied across materials. For example, clays with over 50% kaolinite released 700-500 J/g of heat, while fly ash with about 70% amorphous content released 200-250 J/g.
SAI results and their limitations for SCM classification will also be presented and correlated with pozzolanicity findings.
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