## 4 Results and Discussions  
The internal strains of the specimens in X, Y, and Z directions were recorded from the casting date. The results are presented up to 200 days in Figure 4. The data is presented from 51 days in the figures since external sensors were attached in this day and all the figures in this paper remain in a same time scale for a convenient comparison. Figure 4a shows the average expansion along the specimen dimensions for the reactive specimens and the average volumetric expansions for both reactive and control specimens are presented in Figure 4b. The results for volumetric strains show that reactive specimens were expanded. Conversely, the control specimens had no expansion and the internal strain was relatively constant, only showing small shrinkage over time. However, the volumetric strains for both confined and unconfined specimens were very close. This observation indicates that an imposed confinement in the specimens did not influence the expansion of the entire specimens (volumetric strain). Furthermore, the confinement changed the direction of expansion (Figure 4a). Figure 4: Strain distribution of specimens versus concrete age. (**a**) Directional expansion; (**b**) Volumetric strain. Figure 3: Clustering procedure. (**a**) Energy-frequency based feature extraction; (**b**) Flow chart of data clustering steps. Generally, the expansion through the thickness of the reactive specimens (Z direction) is much larger than the expansion throughout the X-Y plane, due to partial or complete confinement in the plane and lack of steel reinforcement through the thickness. The maximum strains in the Z direction for confined and unconfined specimens are approximately 3.6 and 2.1 times the strain in the Y direction, respectively, at 200 days. The steel frame in the confined specimen causes a reduction of both in-plane strains. In the confined specimen, the strain along the X direction is less than the Y direction, while in the unconfined specimen, the strain along X and Y are almost the same. The strain along the X direction in the confined specimen is 58% of the strain along the X direction in the unconfined specimen at 200 days. However, the strain along the Y direction in the confined specimen is 84% of the strain along the Y direction in the unconfined specimen at 200 days. Moreover, the confinement in X-Y plane for the confined specimen caused an increased strain rate along the Z direction (thickness). The expansion strain rate in terms of time decreases at the point around 150 days, which is named inflection point as seen in Figure 4. The inflection point in volumetric strain is considered as one of the important point for ASR modeling, where the curvature of volumetric strain is changed [27; 28]. The latency and characteristic times (two modeling parameters) are experimentally determined by knowing the location of inflection point [6; 28]. The inflection point is shown in Figure 4b and marked in other figures in this paper. Acoustic emission data was recorded through the internal sensors from the casting day and resonant sensors started recording from the concrete age of 51 days. Filtering AE data is an important step for reducing the amount of non-relevant data for post-processing. The possible sources of false AE data can be friction between the structural components, such as the steel frame and specimens, and water dripping from the chamber ceiling due to high humidity. Two different filtering procedures were developed to minimize the non-genuine data for the internal and external sensors, separately. The filtering is different for the internal and external sensors due to their differences in sensitivity and location. For instance, the internal sensors are much less sensitive than the external sensors and were located inside the specimens, thereby receiving less environmental noise. The AE data below 32 dB and 41 dB for the internal and external sensors was filtered from the data set. Then, the signals were further filtered using a Swansong filtering procedure [29; 30].