## 5 Results and Discussion  
### Slump  
The results of all concrete mixes are presented in Figure 5. According to Figure 5, increasing the value of NS and SP leads to decreasing the slump of concrete, and the impact of SP on that reduction is more significant than NS's. Therefore, the slump dropped by 3% and 6% by using 1% and 2% NS, respectively. Moreover, employing 5% and 10% SP reduces slump by about 4% and 9%, respectively, and using both 2% NS and 10% SP leads to a considerable reduction of about 14%. The previous investigations reported almost the same results thus confirm those presented in this study [46, 47, 48]. [PERSON] et al. [49] stated that adding NS unfavourably decreases the workability of concrete due to raising the viscosity of the mixes. The other previous studies showed a significant increase in the viscosity of concrete and a drop in slump value [50, 51, 52]. According to their results, the slump of concrete declined by 20% when 1.5% NS was used in the mixes. In another study, [PERSON] and [PERSON] [53] performed a comprehensive evolution on the workability of concrete mixes produced with various SP contents. They showed that increasing SP led to reducing the slump value, so that they recommended increasing the superplasticizer in other to increase the slump.  
Additionally, increasing the SF content reduces the slump value (Figure 5). Besides, NS and SP have a negative effect on fibre reinforced HSC. Therefore, the slump dropped by approximately 6%, 11%, 17%, 22% and 28% when 0.1%, 0.2%, 0.3%, 0.4% and 0.5% SF were used, respectively. The reduction in slump due to using SF could be attributed to the bridging role of SF that keeps particles together and makes concrete paste denser [54, 55]. [PERSON] and [PERSON] [56] showed that the slump of concrete declined by 20% when 1% SF were added. In addition, using 2% NS and 10% SP together with 0.1%, 0.2%, 0.3%, 0.4% and 0.5% SF decreased the value of slump by about 19%, 24%, 30%, 36% and 41%, respectively. On the other hand, increasing the PPF content resulted in reducing the slump. Moreover, PPF reduces the slump flow diameter more than SF. This could be attributed to the higher water absorption of polymer fibres in comparison with SF [57]. In Figure 5, adding 0.1%, 0.2%, 0.3%, 0.4% and 0.5% PPF resulted in decreasing the slump by about 7.5%, 14%, 20%, 27% and 34%, respectively. Furthermore, using 2% NS and 10% SP with 0.1%, 0.2%, 0.3%, 0.4% and 0.5% PPF reduced the slump by roughly 20%, 27%, 33%, 40% and 47%, respectively. According to the results reported by [PERSON] et al. [58] the workability of concrete substantially declined when PPF were added due to increasing the contact between concrete paste and fibres.  
The influence of SF and PPF on the workability of HSC can also be seen in Figure 6. According to this figure, using both SF and PPF have a substantial impact on dropping the  
Figure 5: Effect of fibre on the slump of HSC containing NS and SP (**a**) SF and (**b**) PPF.  
value of slump. To evaluate the impact of NS and SP on the workability of fibres reinforced HSC, the value of slump containing different NS and SP contents is illustrated in Figure 6.  
In SF reinforced HSC, a reduction trend occurred by raising the content of SN and SP. A similar tendency was observed in PPF reinforced HSC manufactured with NS and SP (Figure 7). By comparing Figure 7a,b, a greater impact of PPF on slump reduction is observed due to higher water demand and absorption of polymer fires (PPF in this study), in comparison with SF [32].