## 3. Results and Discussion  
### 3.1. Workability  
Figure 2 shows the workability properties of concrete according to the combination of PCE and VMA, and Table 6 shows the shapes of the slump flow. With the addition of PCE without VMA, the slump flow is found to be at 555 mm and 523 mm at the start of the experiment and after 60 min, respectively. From our observation, segregation occurs in the middle of the samples even after 60 min of testing. Moreover, the addition of PCE with only one type of VMA (HL, HH, WG, GG, and ST) shows the largest slump flow at the initial time for the ST sample (693 mm) followed by HL (660 mm), GG (600 mm), and HH and WG (548 mm). After 60 min of testing, ST shows the lowest elapsed ratio of slump flow (4.3%) followed by HH (4.6%), HL (6.1%), GG (7.9%), and WG (24.7%). WG shows a high plastic viscosity and yield stress by strengthening the cohesion of the cement particles. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**\%**} & \multicolumn{4}{c}{**kg/m\({}^{3}\)**} & \multicolumn{4}{c}{**NPCE (Binders \(\times\) wt.\%)**} \\ \cline{3-14}  & **W/B** & **S/a** & **W** & \multicolumn{4}{c}{**Binders**} & \multicolumn{2}{c}{**S**} & **G** & **PCE** & **HPMC** & **WG** & **GG** & **ST** \\ \cline{3-14}  & & & & **C** & **FA** & **BS** & & & & & & \\ \hline Plain & 43.5 & 55.0 & 152 & 228 & 53 & 70 & 983 & 811 & 2.0 & & & & \\ HL & & & & & & & & 2.0 & 0.3 & - & - & - \\ HH & & & & & & & & & 2.0 & 0.6 & - & - & - \\ WG & 43.9 & 55.0 & 154 & 228 & 53 & 70 & 981 & 809 & 2.0 & - & 0.1 & - & - \\ GG & & & & & & & & 2.0 & - & - & 0.1 & - \\ ST & & & & & & & & & 2.0 & - & - & 0.1 \\ HLW & & & & & & & & & 2.0 & 0.3 & 0.1 & - & - \\ HHW & 44.3 & 55.0 & 155 & 228 & 53 & 70 & 979 & 807 & 2.0 & 0.6 & 0.1 & - \\ HLWG & & & & & & & & & 2.0 & 0.3 & 0.1 & 0.1 & - \\ HLWS & & & & & & & & & 2.0 & 0.3 & 0.1 & - & 0.1 \\ HHWG & 45.6 & 55.0 & 160 & 228 & 53 & 70 & 973 & 802 & 2.0 & 0.6 & 0.1 & 0.1 & - \\ HHWS & & & & & & & & & 2.0 & 0.6 & 0.1 & - & 0.1 \\ \hline \hline \end{tabular}  
* C: cement, FA: fly ash, BS: blast furnace slag, S: fine aggregate, G: coarse aggregate, HPMC: hydroxypropyl methylcellulose, WG: welan gum, GG: guar gum, and ST: starch.  
\end{table} 
Table 5. Combinations of NPCE and mixture design for NSHFC. Due to the smaller slump value of the WG samples, segregation does not occur. In the case of adding PCE with HL, ST, or GG, the slump value is over 600 mm, with the occurrence of segregation. In particular, ST shows the highest slump flow value, but shows the most severe segregation. This is caused by the lowest plastic viscosity and yield stress. Thus, it is confirmed that there is a limit in securing the fluidity and segregation resistance when only one type of VMA is added. Aside from this, with the addition of PCE with two types of VMA (HLW and HHW), the initial slump flows are found to be 543 mm and 540 mm for HLW and HHW samples, respectively. After 60 min of testing, the elapsed ratio of slump flow was larger in HLW samples (17.1%) compared to HHW samples (7.9%). It was expected that, with the increase in the amount of HPMC (0.3 to 0.6%), the adsorption disturbance of the PCE will increase, and the dispersion of cement particles will decrease. Furthermore, with the addition of PCE with three types of VMA (HLWG, HLWS, HHWG, and HHWS), the initial slump flow of HLWS is the largest (630 mm), followed by HLWG and HHWS (613 mm), and HHWG (595 mm). After 60 min of testing, the elapsed ratio of slump flow is the lowest for HHWS (3.7%), followed by HHWS (6.3%), HHWG (11.3%), and HLWG (14.7%). The increase in the amount of HPMC decreases the elapsed ratio due to the characteristics of the HPMC, which will delay the setting time of the cement paste. On the other hand, in the case of the HH (HPMC 0.6%) combination, segregation does not occur due to the slump flow value. In summary, when the amount of HPMC increases from 0.3% to 0.6%, the cohesion of the concrete is strengthened.