# Acoustic Emission Analysis of the Cracking Behavior in ECC-LWSCC Composites
## 8 Conclusions  
For the purpose of the damage characterization of ECC-LWSCC composite beams under flexural loading, an experimental study was conducted using several AE analyses. Six beams were tested, each constructed with different fibers (PVA or SF) and repaired in various locations: two beams were fully cast with ECC (ECCP and ECCS), two beams were repaired in compression (ECCP-C and ECCS-C), and two beams were repaired in tension (ECCP-T and ECCS-T). Three sensors monitored the changes resulting from crack development until failure. The post-testing analysis of AE data yielded the following conclusions:  
* All six beams failed in flexural mode after reinforcement bars in the tension zone yielded and the concrete in the compression zone was crushed. The control beams (ECCP and ECCS) showed the highest ultimate load capacity, followed by beams repaired in tension (ECCP-T and ECCS-T), and then beams repaired in compression (ECCP-C and ECCS-C). PVA fibers exhibited superior performance compared to steel fibers at the first crack load. However, steel fibers enhanced beam performance at the ultimate load stage;
* Analysis of both the \(b\)-value and \(lb\)-value proved useful in evaluating crack growth throughout the testing. A general decrease in \(b\)-value after the detection of the first crack reflected ongoing crack development. The \(lb\)-value exhibited a fluctuating trend, with sudden vertical drops indicating high cracking activity. The first crack was consistently detected, coinciding with the first decreasing trend in \(b\)-value and the first increase in \(lb\)-value across all beams;
* Different fiber types impacted the number of hits and CSS among the tested beams. Beams fully cast or repaired with PVA fibers displayed higher hits and CSSs at the first crack due to dispersion effects. However, at the ultimate load stage, beams with SFs demonstrated higher hits and CSSs due to enhanced compressive and pullout strengths balancing the dispersion effect of the PVA fibers;
* Variations in sensor location significantly affected wave propagation characteristics in ECC-LWSCC composite beams, specifically signal amplitude. Signal amplitude values varied between sensors due to signal attenuation and was particularly evident in all composite beams due to material homogeneity. Fully cast ECC beams did not experience signal attenuation, with signal amplitude values closely aligned across the three sensors;
* RA vs. AF analysis successfully characterized the failure modes in all the beams, predominantly in the tensile cracking zone indicating flexural failure. RA analysis effectively determined the failure modes, corroborating the experimental results;
* Overall, these findings confirmed the usefulness of AE analysis in understanding the behavior of ECC-LWSCC composite beams under flexural loading, highlighting the influence of fiber type, repair location, and sensor placement on structural performance and failure characteristics. The practical application of these results includes the implementation of AE monitoring in assessing LWSCC repaired with ECCs. In particular, AE analysis can be used as a useful tool for evaluating the structural performance of LWSCC beams repaired with an ECC layer. Conceptualization, A.H. and A.A.; methodology, Y.Z. ; software, Y.Z. ; validation, Y.Z., A.A. and A.H.; formal analysis, Y.Z. ; investigation, Y.Z. ; resources, A.H.; data curation, A.A.; writing--original draft preparation, Y.Z. ; writing--review and editing, A.A. and A.H.; visualization, A.A.; supervision, A.A. and A.H.; project administration, A.H.; funding acquisition, A.H. All authors have read and agreed to the published version of the manuscript. This research received no external funding. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.