Definition of setting time

Q. What is meant by setting of cement paste or concrete?

A. The paste formed when cement is mixed with water remains plastic for a not very long time. It stiffens and sets. The setting process is arbitrarily divided into stages, time of initial setting and time of final setting, depending on the resistance to penetration by a probe. Before the time of initial setting, it is still possible to disturb the concrete and remix it without injury. Later revibration can be beneficial, but as the reactions between the cement and water continue, the mass loses its plasticity. At the time of final setting, the concrete has become rigid and fractures rather than flows as increasing stress is applied.

References: SP-1(02); ACI Physical Testing of Cement Training Video; The Contractor's Guide to Quality Concrete Construction; ASTM C403; ASTM C191

Topics in Concrete: Cementitious Material; Concrete Fundamentals; Materials