Effect of addition of pozzolanas in concrete: ● It reacts with calcium hydroxide and decreases the heat of hydration. ● The early strength decreases but the ultimate strength remain almost the same. ● It also helps in improving workability and resistance against external agents. ● Puzzolana finds its applications where the slower gain of strength is required. ● Silica fume, fly ash, blast furnace slag, etc. are the most commonly used pozzolanic materials.