**3. Results and Discussions**

*3.1. Slump Test*

The settlement time of NSVC was different from that of HPVC since the latter had contained the superplasticizer; it outspread at a slower rate until 8 s after the lifting of the cone, while NSVC was stable within 3 s. The slump test results were shown in Table 4. Both results were considered acceptable for good workability during casting of concrete, while here the weak point of the slump test can appear when the HPVC was behaving acceptable for the slump test, but the mixture was very stiff that could not perfectly fill the mold without extra vibration.

**Table 4.** Slump test result of normal strength-vibrated concrete (NSVC) and high-performance highly-viscous concrete (HPVC) mixes, a flow test result of high-performance self-consolidating concrete (HPSCC) and high-strength self-compacted concrete (HSSCC), and restricted flow test result for HPSCC and HSSCC.


### *3.2. Flow Test*

The slump flow test results were shown in Table 4. The flowing of both concrete types was such that neither bleeding nor segregation had occurred. The flow diameter of micro silica concrete (HPSCC) was 810 mm with T500 of 2.62 s, while the flow diameter of fly ash concrete (HSSCC) was 750 mm, which was lower by 8%, but the T500 was 3.8 s and was higher by 44%. The results also proved that the micro-silica helped in achieving a better flowability (in addition to the higher strength) because the fly ash particles were relatively larger compared to microparticles of the silica. Research showed that the additional grinding of fly ash did not cause workability loss of SCC and the plastic viscosity has increased [31,56].

The flow of 740–900 mm is used as a conformity limit for highly congested structures, and the conformity criteria of 2–5 s is used for the T500 when the improvement of segregation-resistance is necessary. T500 of less than 2 s is applied for very congested structures, better surface finishing, and risk of bleeding or segregation. From a practical point of view, increasing the initial flow head can also increase the flow energy necessary to transport coarse aggregate [1,56]. The ability of SCC mixtures to resist segregation was determined based on the assigned segregation index (SI). If there is no obvious accumulation of coarse aggregate particles and no free water flowing around the concrete's perimeter, the mixture is assumed to have full segregation resistance (SI = 0). If the mixture exhibited an apparent accumulation of coarse aggregate or a small amount of water flowing, the mixture is unlikely to segregate (SI = 1). In case of obvious accumulation of coarse aggregate or free water, the SCC is likely to segregate (SI = 2). Finally, a large amount of accumulated coarse aggregate or a large amount of free water flowing indicates that the concrete will segregate, and the mixture must be rejected [25].
