# Acoustic Emission Analysis of the Cracking Behavior in ECC-LWSCC Composites
## 7 Results and Discussion
### Impact of Fiber Type on AE Parameters  
Table 6 shows the values of the AE parameters, including the number of hits and cumulative signal strength (CSS) at the first crack and ultimate load.  
As observed from Table 6, the effect of fiber type (PVA or SF) was most evident in the number of hits and CSS. It can be concluded that beams repaired or fully cast with PVA fibers generally displayed a higher number of hits compared to beams repaired or fully cast with SFs, specifically at the first crack. For ECCP and ECC, the average number of hits and CSS at the first crack were 2859 hits, 2.92 \(\times\) 10\({}^{7}\) pVs, and 2384 hits, 2.46 \(\times\) 10\({}^{7}\) pVs, respectively. ECCP-T and ECCS-T showed an average number of hits of 2990 and 2666 hits, respectively, and CSS values of 3.07 \(\times\) 10\({}^{7}\) pV.s and 3.01 \(\times\) 10\({}^{7}\) pVs, respectively.  
Beams repaired in compression, however, were not significantly affected by these phenomena, as the material existing on the tension side was LWSCC. The rationale behind  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Beam**} & \multirow{2}{*}{**Sensor**} & \multicolumn{2}{c}{**\(b\)-Value**} & \multicolumn{2}{c}{**_lb_-Value**} \\ \cline{3-6}  & & **First Crack** & **Ultimate Load** & **First Crack** & **Ultimate Load** \\ \hline \multirow{3}{*}{ECCP} & CH-1 & 2.78 & 0.86 & 1.47 & 1.79 \\  & CH-2 & 1.14 & 0.24 & 1.45 & 1.82 \\  & CH-3 & 2.64 & 0.41 & 1.63 & 2.08 \\ \hline \multirow{3}{*}{ECCS} & CH-1 & 1.77 & 0.20 & 1.48 & 2.09 \\  & CH-2 & 0.96 & 0.09 & 1.73 & 1.96 \\  & CH-3 & 1.44 & 0.12 & 1.65 & 2.05 \\ \hline \multirow{3}{*}{ECCP-C} & CH-1 & 2.76 & 1.02 & 1.67 & 1.74 \\  & CH-2 & 1.86 & 0.61 & 1.79 & 1.66 \\  & CH-3 & 2.71 & 0.74 & 1.77 & 1.65 \\ \hline \multirow{3}{*}{ECCS-C} & CH-1 & 1.52 & 0.97 & 1.85 & 1.96 \\  & CH-2 & 1.51 & 0.69 & 1.88 & 1.97 \\  & CH-3 & 1.16 & 0.78 & 1.82 & 1.95 \\ \hline \multirow{3}{*}{ECCP-T} & CH-1 & 0.93 & 0.51 & 1.88 & 2.052 \\  & CH-2 & 0.74 & 0.36 & 1.88 & 2.042 \\ \cline{1-1}  & CH-3 & 0.84 & 0.46 & 1.75 & 2.064 \\ \hline \multirow{3}{*}{ECCS-T} & CH-1 & 1.08 & 0.63 & 1.82 & 1.62 \\ \cline{1-1}  & CH-2 & 0.82 & 0.38 & 1.68 & 1.89 \\ \cline{1-1}  & CH-3 & 0.96 & 0.52 & 1.72 & 1.86 \\ \hline \hline \end{tabular}
\end{table}
Table 5: _b_-value and _lb_-value at first crack and ultimate load.  
the higher number of hits and CSS in beams incorporated with PVA fibers is that PVA fibers generally have a lower density than SFs. The lower density and smaller size of PVA fibers allow for more dispersion in the ECCS at the same fiber volume as SFs. Therefore, a higher number of PVA fibers are present, which delay crack formation compared to SFs [9].  
Conversely, at ultimate load, the number of hits displayed by beams incorporating/repaired with PVA fibers is very comparable to those repaired with steel fibers. For instance, ECCP and ECCS displayed an average number of hits of 26734 and 27500 hits, respectively, and CSS values of 40.8 \(\times\) 10\({}^{7}\) PVs and 43.2 \(\times\) 10\({}^{7}\) pVs at ultimate load, respectively. ECCP-T and ECCS-T exhibited average values of number of hits and CSSs of 24055 and 2588 hits, 32.5 \(\times\) 10\({}^{7}\) pVs and 34.6 \(\times\) 10\({}^{7}\) pVs at ultimate load, respectively. These parameters correlated well with the number of cracks in the ECCS-T and ECCP-T beams (30 and 37 cracks, respectively) [9]. A similar trend was also observed in the cracking activities of ECCP and ECCS beams at ultimate load (34 and 37 cracks, respectively) [9]. Therefore, the number of hits and the CSS were found to be useful in demonstrating the impact of the different fiber types used in this study.