2.3.2. Process of Experiment

Before collecting data from the shrinkage experiment, we first completed the fabrication of each group of wall panels (Table 3) and the installation of strain sensors, as shown in Figure 6. The placement of the strain sensor, as shown in Figure 7, was determined by the distribution of S0 cracks, which is explained in the next chapter.

**Figure 6.** Experimental process: (**a**) pouring concrete; (**b**) placing embedded strain sensor; (**c**) surface processing; (**d**) pouring GRC material; (**e**) leveling the GRC surface; (**f**) placing surface strain sensors; (**g**) connecting the static strain tester; (**h**) covering film maintenance.

**Figure 7.** Strain sensor location in the composite wall panel.

The specific process was as follows.

(1) Brush the surface of the template with release oil and then pour the concrete to the height of the specified scale of the template;

(2) Vibrate the concrete and bury the embedded strain sensor at the center of the concrete;

(3) Machine the surfaces of wall panels of different types;

(4) Pour the mixed GRC material into the initial setting concrete and level the surface with a roller;

(5) Install and fix the surface strain sensor at the center of the GRC layer;

(6) Switch on the static strain tester and cover with a film for maintenance.

Since the shrinkage deformation of the wall panel is influenced by the ambient temperature and the humidity, in the experiment, we recorded daily indoor and outdoor temperatures and humidity in the morning, the afternoon, and the evening during the test period while taking the shrinkage strain measurement. The average value of the temperature in the three periods was taken and plotted as the temperature and humidity curve, as shown in Figure 8. As shown, the temperature amplitude was lower in the indoor environment than in the outdoor environment, whereas the air humidity was higher in the indoor environment than in the outdoor environment. Since cement-based cementitious materials are more suitable for maintenance and use in an environment with small temperature difference and high humidity [32], the outdoor environment, compared with the indoor environment, is more severe and places higher requirements on GRC-PC composite wall panels to resist cracking.

**Figure 8.** Temperature and humidity curves during the test period: (**a**) Indoor and outdoor temperatures vs. time curves; (**b**) indoor and outdoor humidity vs. time curves.

#### **3. Results and Discussion**

#### *3.1. Experimental Results of Mechanical Properties of Materials*

Tables 4 and 5 list the measured compressive strength and elastic modulus, respectively. From Table 4, we found that the compressive strengths of three GRC and concrete test

blocks reached the standard compressive strength value on the 28th day, and the average value was within the error range.


**Table 4.** Measurement results of compressive strength experiment.

**Table 5.** Measurement results of elastic modulus experiment.

