3.5.1. Penetration Resistance Test for Determining Setting Time

In order to measure the mortar setting time, the penetration resistance of the mortar was measured using a standard needle at a regular time interval according to ASTM C 403 [52]. From the plot of penetration resistance versus elapsed time, the initial and final setting times were determined. For mortar with 50% GGBFS content, the setting time could not be measured under curing conditions of 5 ± 1.5 ◦ C. Therefore, the time when the compressive strength of the mortar reaches 4 MPa was considered as the final setting time by the alternative method proposed in ASTM C 1074 [21].
