*2.1. Specimen and Chamber Preparation*

In this study, three large-scale reinforced concrete blocks were cast. Two specimens were reactive and one was a control specimen (Figure 1). Reactive specimens are the specimens that experience expansion due to alkali-silica reaction. Two layers of steel reinforcement mesh were located at the top and bottom surfaces of the specimens. The reinforcement mesh includes US #11 Grade 60 with a nominal diameter of 36 mm (1.41 inches) at 25 cm (10 inches) spacing (Figure 2). The specimens have 7.62 cm (3 inches) cover at top and bottom of the specimens. Moreover, the square steel plates were installed on the ends of the rebar to achieve the full development length in a relatively short distance inside the specimens. For concrete mixture, 350 kg/m<sup>3</sup> cement, 175 kg/m<sup>3</sup> water, 1180 kg/m<sup>3</sup> coarse aggregate, and 728 kg/m<sup>3</sup> fine aggregate were used for both reactive and control specimens. The main difference between the specimens was using of NaOH or LiNO3. In the reactive specimens, 9.8 kg/m<sup>3</sup> NaOH solution was added, while in the control specimen 1.9 kg/m3 LiNO3 was included in the mixture [22].

The coarse aggregates in both control and reactive specimens were greenschist coarse aggregates from North Carolina, which were highly-reactive. Non-reactive manufactured sand and low-alkali Portland cement Type II were also utilized in the concrete mixture. Water to cement weight ratio for both control and reactive specimens was 50%. To increase the alkali content of reactive specimens, 50% sodium hydroxide solution was added to the mixture for reactive specimens. Additionally, a 30% lithium nitrate solution was added to the control specimens to mitigate the ASR effect. More details regarding concrete mixture design was presented by Hayes et al. [22].

The specimens shown in Figure 1 have a cubic shape with dimensions of 3.50 m × 3.0 m × 1.0 m (136 inch × 116 inch × 40 inch). There are two reactive specimens; confined and unconfined specimens. A rigid steel brace was utilized to restrain the confined specimen from expanding in the lateral plane. The unconfined specimen does not have a steel brace in its plane. The two reactive specimens resemble the different stress boundary conditions found in real structures. A 1.5 mm layer of polyethylene was employed between the concrete and the steel frame in the confined specimen to reduce friction. More detailed information about the specimens and steel frame design were presented in Hayes, et al. [22]. In this experiment, the specimens stand on four short, steel columns (76 cm height) to provide access to the bottom of the specimens.

Each specimen's formwork was removed 12 days after casting which gave them time for final finishing and concrete setting. After casting, the specimen surfaces were sprayed with curing compound and covered with wet burlap and plastic sheets to reduce moisture loss and cracks from shrinkage during drying. The burlap was kept wet until chamber construction was complete [22].

A large chamber with the dimensions of 16.2 m long, 7.3 m wide, and 3.7 m high was constructed around the specimens to control the temperature and relative humidity of the environment. The chamber was equipped with systems that kept the specimens at the environmental temperature of 38 ± 1 ◦C and humidity of 95% ± 5%. The environmental chamber was initiated 26 days after casting and operated continuously except for shutdown for measurements and inspections [22].

**Figure 1.** Test specimens.

**Figure 2.** Acoustic emission (AE) sensor locations. (**a**) Internal AE sensors (broadband); (**b**) External AE sensors (resonant); (**c**) Internal sensors 3 and 6 installation; (**d**) Internal sensors 1, 2, 4 and 5 installation.
