## 3 Results and Discussion  
### Test Phenomenon  
According to the experimental phenomena, stress performance and failure morphology of concrete shear wall specimens CGSW-2 and CGSW-3 mixed with coal gangue were similar to those of conventional concrete shear wall specimen RFSW-1. Horizontal cracks first appeared at the bottom of the specimen. As the horizontal displacement increased, horizontal cracks gradually developed obliquely, and the inclination angle of the diagonal crack increased with crack height. New horizontal cracks appeared continuously along the height of each specimen. With a further increase in horizontal displacement, the crack width became larger and more intensive. At the same time, a vertical crack appeared at the bottom of the hidden column. Finally, a main horizontal crack was formed at the bottom of each specimen. The concrete at the corner of the specimen was crushed from the specimen. At the same time, the longitudinal reinforcements of the specimen could be seen buckling and were exposed, and the bearing capacity of the specimen decreased gradually.  
Figure 6: Test setup (**a**) Schematic diagram (**b**) Practice diagram.  
Figure 7: Strain gauge layout (**a**) Reinforcement strain gauges (**b**) Concrete strain gauges.  
From the failure process and morphology of specimen RFSW-1, the cracks of the whole specimen were dense, uniform, and roughly symmetrical. In addition, the cracks were mainly concentrated at the bottom of the specimen. The height of the concrete falling off from the corner of the specimen wall was 75 mm, and the width was 50 mm. The highest crack was 550 mm from the foundation beam, and most of the cracks were horizontal-oblique development cracks. The specimen was fully damaged and had a typical bending-shear failure mode. Failure morphology of specimen RFSW-1 is shown in Figure 8a.  
From the failure process and morphology of specimen CGSW-2, the crack distribution and cracking process of the specimen were not significantly different from those of specimen RFSW-1, but the number of cracks was slightly greater than that of specimen RFSW-1. Concrete falling ranges of the specimen corners on both sides of the specimen were \(150\times 75\) mm and 75 \(\times\) 50 mm, respectively. The highest crack was 700 mm from the foundation beam, and the specimen exhibited bending-shear failure. Failure morphology of specimen CGSW-3 is shown in Figure 8c.  
Figure 8: Failure morphology of the specimens (**a**) RFSW-1 (**b**) CGSW-2 (**c**) CGSW-3 (**d**) Comparison.  
It can be seen from the destruction process of the three specimens that the difference between the coal gauge-made shear wall and the ordinary concrete-made shear wall is not obvious. The damaged area for the former is larger, because the coal gauge shear wall is more seriously damaged than the natural coarse aggregate when it is subjected to lateral cyclic loading. As the spontaneous combustion coal gauge forms more flaky blocks in the coal seam, it is easier to form needle flakes when crushed. Therefore, the grain shape of the spontaneous combustion coal gauge is worse than that of natural coarse aggregate. Nevertheless, since the needle-like aggregate will adversely affect the working capacity and strength of concrete, the shear wall made of coal gangue has a larger area of damage than the ordinary concrete shear wall.