*3.3. Restricted Flow Test*

Results of the J-Ring test were shown in Table 4, noting that the restricted flow can decrease the flow diameter and T500, while the rate of restriction in the micro-silica concrete (HPSCC) was more than that of the fly ash containing concrete (HSSCC) compared to unrestricted flow. The difference in height inside and outside the ring was clearly showing a better flowability of the HPSCC, since the thickness of the concrete along the diameter of flow was almost homogeneous, neither bleeding nor segregation were observed. Restriction of concrete flow was causing the reduction in flow diameter by 6.2% and 1.3%, respectively for HPSCC and HSSCC, but the HSSCC mix had exhibited a little variation inside and outside the ring, not reaching the limit of segregation. The difference between the T500 values measured using the J-Ring test and the slump flow test should not be more than 2–4 s according to ASTM C1621 [57].

#### *3.4. Density of the Hardened Concrete*

Concrete density is an important property that is used in the design of concretestructures through calculating the self-weight of the members. Table 5 shows the concrete density for the four concrete mixes considering the age of concrete. It can be observed that concrete densities were decreased with time. This phenomenon can be justified by continuous chemical reactions inside the concrete structure. The ratio of weight loss was between 0.5 to 2.5% when comparing 28-day densities with that of 6 months. It can also be noted that the two SCC mixes had less standard deviation (SD) than that of vibrated concrete mixes. When considering the shape and thickness of the concrete, neither systematic relation nor clear differences could be found between tile shaped specimens and the cubes, when comparing the 28-day densities in Table 5.


**Table 5.** Density of 100 mm cubes and tile shaped specimens, and absorption test results. Abbreviations: High-performance self-consolidating concrete (HPSCC), high-strength self-compacted concrete (HSSCC), normal strength-vibrated concrete (NSVC), and high-performance highly-viscous concrete (HPVC).

#### *3.5. Water Absorption by Immersion*

Results of the water absorption test are shown in Table 5, and each value in the table was representing the average of 4 tests. The results show that the water absorption of the NSVC was the largest due to the high void ratio, larger particle sizes, and less binder content compared to other mixes. Very low water absorption was observed in the HPVC mix due to the high binder content and improved packing of the particles as a result. Water absorption of the NSVC was 11% higher than that of the HSSCC; it was 2.4 and 4.1 times higher than that of HPSCC and HPVC, respectively. Similar results of about 2% water absorption were obtained in the previous study [28], while for higher fly ash replacements of 70 and 90%, the absorption was increased to 3.5 and 4.7%, respectively. Research showed that for an HPC with a water–binder ratio of 0.40 at 28 days, the water permeability was about 9 times higher than an HPC with a water–binder ratio of 0.23 [17].
