Addition of gypsum to cement:
[amp_mcq option1=”reduces setting time of cement” option2=”produces very light colour cement” option3=”increases setting time of cement” option4=”shining surface is formed” correct=”option3″]
This question was previously asked in
UPSC NDA-2 – 2015
– Gypsum (calcium sulfate dihydrate) is added to the cement clinker during grinding to act as a retarder.
– Gypsum reacts with C₃A to form ettringite, which precipitates on the surface of the C₃A particles, forming a barrier that slows down the rapid hydration of C₃A.
– This allows sufficient time for the cement paste or concrete to be mixed, transported, placed, and finished before it begins to harden.