The measurement of fresh SCC properties

The measurement of fresh SCC properties was started immediately after mixing (9 min after the initial contact of water with cement). The slump flow values were represented by the mean diameter (measured from two perpendicular directions) of the concrete spread after lifting the standard slump cone. The final diameter was determined in the slump flow test, and the time required for the concrete to spread to a diameter of 500 mm (T50) was recorded. Once a slump flow of 650 mm was ensured, the visual LC Biotin index (VSI) of the mixtures was determined according to ASTM C 1611 [31]. Then, the rheological parameters (torque plastic viscosity and apparent yield stress) were evaluated using a coaxial cylinder concrete rheometer (ConTec 4SCC). A four-bladed vane rotating coaxially was used for the impeller. The container of the rheometer had an internal diameter of 240 mm and a endometrium depth of 240 mm, allowing a concrete sample volume of approximately 8 L. Following the rheology tests, thixotropy tests were performed. In order to determine the effect of elapsing time, the rheological parameters were measured at 0 and 50 min after mixing. To prevent the effect of evaporation, the fresh mixtures was covered by plastic sheets during standstill time interval. At the end of 50 min rest, the concrete was remixed for 2 min and the measurements of the fresh properties were repeated. The 28-day compressive strength of the mixtures was also determined according to ASTM C 39 [32]. The average compressive strength of three specimens was recorded for each mixture.