What is pozzolanicity?

Pozzolanicity is the property of a material to react with calcium hydroxide in the presence of moisture and form compounds with binding properties that harden over time. Pozzolanic materials can be natural or artificial, such as volcanic ash, fly ash, silica fume, and metakaolin. When mixed with Portland cement, pozzolanic materials can enhance the performance of concrete by improving its strength, durability, sustainability, and resistance to chemical attack and corrosion. The pozzolanic reaction also consumes calcium hydroxide, which reduces the alkalinity of concrete and mitigates the risk of alkali-silica reactions. Pozzolanicity is thus an important factor in the selection and design of concrete mixes, particularly in applications that require high performance and long-term reliability.