*2.2. Experiment on Mechanical Properties of Materials*

The compressive strength and the modulus of elasticity are the basic mechanical properties of materials. Tests were carried out on the mechanical properties prior to the fabrication of the test elements to ensure that the material strength met the requirements. The twelve test blocks for the modulus of elasticity and compressive strength tests were divided into four groups of three blocks each based on the curing time listed in Table 2.

**Table 2.** Parameters of material test block.


After curing each group of test blocks for the corresponding days, we installed strain sensors on their surface and connected the static strain tester. We then employed the compression testing machine to carry out a pressure test on the test blocks until they were destroyed. Figure 4 shows the experimental process.

**Figure 4.** Experimental process of mechanical properties of materials: (**a**) Manufacture of concrete test block; (**b**) manufacture of GRC test block; (**c**) grouping and pasting of test blocks; (**d**) loading of test block.

The compressive strength was calculated using the following formula:

$$F\_{\rm cl} = \frac{F}{A'} \tag{1}$$

where *Fcu* is the compressive strength (MPa) of C30 concrete and GRC cube specimens; *F* is the failure load (N) of the specimen; *A* is the bearing area (mm2) of the specimen.

The measurement and the calculation formula of the elastic modulus were:

$$E\_c = \frac{F\_a - F\_0}{A} \times \frac{L}{\Delta n'} \tag{2}$$

where *Ec* is the elastic modulus of the specimen; *Fa* is the load at which the stress reaches one third of the axial compressive strength value; *F*<sup>0</sup> is the initial load (N) when the stress is 0.5 MPa; *L* is the measuring gauge distance (mm); *A* is the bearing area of the specimen (mm2); Δ*n* is the average value (mm) of the deformation on both sides of *Fa* from *F*<sup>0</sup> loading.

#### *2.3. Shrinkage Experiment of GRC-PC Composite Wall Panels*

#### 2.3.1. Specimen Design

A total of seven groups of components (S0 to S6) were designed for the shrinkage experiment. S0 and S1 were panels made of GRC without and with glass fiber, respectively; S2 was a panel made of concrete; S3 to S6 were GRC-PC composite wall panels made

according to Figure 1, which omitted the concrete structure layer and the insulation layer, as shown in Figure 5. Table 3 lists the specific parameters. Because of the limitations of the experimental site, the length and the width of the wall panel were designed to be 1000 mm × 1000 mm, and the thicknesses of the GRC and the PC layers were set to 15 mm and 60 mm, respectively. For the interface between GRC and PC, two commonly used concrete surface processes were adopted: smooth surface (surface smoothing) and rough surface (surface grabbing).

**Figure 5.** Three-dimensional model of a composite wall panel.



The design idea of the components was as follows: S0 panel was a member without glass fiber, which was mainly used to observe the way of crack development so as to determine the location of the strain sensor. Other panels (S1 to S6) took the interface type and the environment as variables to determine the applicable structural type of GRC-PC wall panel.
