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Q: Flash set of ordinary Portland cement paste is
  • A. Premature hardening
  • B. Surface hardening only
  • C. Hardening without development of heat of hydration
  • D. All the options are correct
Correct Answer: Option A - Flash set – It is the immediate stiffening of cement paste in a few minutes after mixing water. It is accompanied by large amount of heat generation upon reaction of C3A with water. • Flash set of ordinary Portland cement paste is premature hardening. • Gypsum (2 to 3%) is placed in cement to prevent flash-set.
A. Flash set – It is the immediate stiffening of cement paste in a few minutes after mixing water. It is accompanied by large amount of heat generation upon reaction of C3A with water. • Flash set of ordinary Portland cement paste is premature hardening. • Gypsum (2 to 3%) is placed in cement to prevent flash-set.

Explanations:

Flash set – It is the immediate stiffening of cement paste in a few minutes after mixing water. It is accompanied by large amount of heat generation upon reaction of C3A with water. • Flash set of ordinary Portland cement paste is premature hardening. • Gypsum (2 to 3%) is placed in cement to prevent flash-set.