## 4 Results and Discussion  
Data on AESL are analyzed in two dimensions and investigated with respect to the sequential hits experienced. Shown in Figure 7 is the AESL hits and maximum distances across each axis considered. In addition, Figures 8-10 show the maximum distances of AESL in two dimensions. The progression of maximum distances for all types of RC beams along the \(x\)-axis showed good correlation to damage. However, the behavior of the changes in maximum distances of AESL behaved linearly. The progression of maximum distances along the \(y\)-axis, which represent the width of AESL hits, is 4 cm or more for a load greater than 60%. This showed that the spread of AESL hits after 60% ultimate load is more than 40% of the width of the concrete. For the progression along the \(z\)-axis, which is the movement along the height, the WC40 experienced 3 cm or more, while WC60 encountered 4 cm or more for a load more than 60% of the ultimate load. This showed the ductility of WC60 compared to WC40, where AESL hits were spread out farther. Figure 5: Acoustic emission and four-point bending test setup. Figure 6: Acoustic emission and four-point bending test setup. Figure 8: Average maximum AESL along the \(x\)-axis. Figure 7: Acoustic emission source location (AESL) for Specim 1 WC60 Design C.  
Figure 9: Average maximum AESL along the \(y\)-axis. The discussion above focused on the two-dimensional analysis of AESL. Using all data along each axis, a three-dimensional graph was investigated. In Figure 11, AESL hits were plotted and compared to each beam reinforcement with water-cement ratios of 0.40 and 0.60. Quantitative analysis for the figure presented was difficult to carry out, but generally the location of the AESL hits becomes wider as the water-cement ratio increases. This showed that, with respect to each type of reinforcement design, the concrete with the higher water-cement ratio is more ductile than that with the lower water-cement ratio. In addition, most of the AESL were positioned above the mid-height of the beam. This was maybe due to the crack formation where the AESL is represented by the crack tip. The geometric positions of the AESL upon loading was difficult to analyze due to the three-dimensional axes, where the width of the crack formation should be considered in the crack progression. In this paper, CHV was considered to represent the analysis in three dimensions. The assumption in AESL is that it served as vertices in CHV formation where it occupies the space by the mortar or the ITZ. These points are the weakest link inside the concrete mixture. The surfaces or edges of the CHV generated do not represent the surface of the mortar or ITZ. The inclusion of aggregates is assumed to be negligible in solving the CHV [4]. Figure 11: Acoustic emission (AE) hits from L1 to L4 for the six variations of RC beams. Figure 10: Average maximum AESL along the \(z\)-axis. Shown in Figure 12 are the WC40 and WC60 specimens with beam design A in isometric view, where the CHV progression increases according to L1, L2, and L3. The quantity of the CHV showed that WC60 has a greater volume than WC40 of the same beam reinforcements. This showed the ductility of WC60 compared to WC40, where AESL hits spread out more widely when crushing is experienced in the compression zone. In Figure 13, the WC40 and WC60 specimens with beam design B are shown from the top view of the concrete specimens. The CHV also increases with the loading/unloading branch L1, L2, and L3. Similar to beam design A in Figure 11, the WC60 specimen spreads its volume wider than the WC40. This indicates the ductility of WC60 when subjected to a four-point bending test. The CHV progression for beam design B is shown in Figure 14 along its side elevation. The CHV increases with the load progression L1, L2, and L3. In this view, the spread of the AESL along the vertical axis decreases when load is increased. The CHV progression for beam design C is shown in Figure 15 along its front elevation.