'Pozzolanic materials' contribute to concrete strength by:
Choose the correct answer
Replacing aggregates with lighter materials
Reacting with Ca(OH)2 from cement hydration to form additional C-S-H gel — improves later strength and durability
Providing colour pigments to concrete
Reducing the cement percentage only
Correct Answer
B. Reacting with Ca(OH)2 from cement hydration to form additional C-S-H gel — improves later strength and durability
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Pozzolana (IS 1344/IS 3812): reactive siliceous/aluminous material that reacts with calcium hydroxide (Ca(OH)2) liberated during cement hydration — secondary C-S-H gel formed. Reduces: permeability, alkali-silica reactivity, heat of hydration, CH content (attacks durability). Increases: later strength, chemical resistance. Examples: fly ash (Class F/C), GGBS, silica fume, rice husk ash.
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