Technical Questions

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False and flash set

Q. What are false set and flash set?


A. False set is the rapid development of rigidity in freshly mixed paste, mortar, or concrete without the evolution of much heat. Plasticity can be regained by further mixing. Flash set is also the rapid development of rigidity, but with the evolution of considerable heat. Plasticity cannot be regained. Rapid development of rigidity would interfere with

delivery and placement operations. Flash set would make concrete unusable, and concrete hardened in the mixer could not be removed easily.


References: SP-1(02); ACI Physical Testing of Cement Training Video; ASTM C403; ASTM C191; ASTM C266; ASTM C953

Topics in Concrete: Concrete Fundamentals

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