# Characteristics of Restrained Drying Shrinkage on Arched Steel Fiber-Reinforced Concrete
## 3 Experimental Results
### Deck Slab Drying Shrinkage Tests  
Figure 7 shows the aging results for the drying shrinkage strain measured by the gauges embedded at the surface and at the center of each deck slab specimen. For the surface measurements, the strain increased at the beginning but decreased after three days of aging due to the drying shrinkage of the concrete that occurred on the surface. The tendency of the drying shrinkage strain of the wire mesh deck slab to decrease is similar to that of the SFRC deck slab; however, the drying shrinkage strain of the wire mesh deck slab increased more than that of the SFRC deck slab as the aging progressed. After 56 days of aging, the drying shrinkage strain of the SFRC deck slab at the surface was approximately 12.4% less than that of the wire mesh deck slab. The reason for this outcome may be that the significant concrete drying shrinkage occurred in the part of the wire mesh deck slab that did not contain wire mesh, as only the upper part of the concrete was reinforced with wire mesh, whereas for the SFRC deck slab, the entire cross-section of the concrete was reinforced with arched steel fiber.  
With regard to the drying shrinkage strain at the center of the specimen, the strain increased at the beginning (as it did at the surface), but started to decrease after seven days of aging. The strain continued to decrease and became almost constant after 16 days of aging. The likely reason for this outcome is that the drying shrinkage of the concrete at the bottom of the deck slab was restrained by the deck plate, whereas drying shrinkage occurred on the surface of the deck slab due to exposure to the external environment. Therefore, the drying shrinkage strain at the center of the specimen did not decrease with an increase in aging because compressive force acted on the top of the deck slab and tensile force acted on the bottom.  
Figure 6: Restrained drying shrinkage strain during aging: (**a**) plain concrete and (**b**) concrete reinforced with arched steel fiber content of 14.8 kg/m\({}^{3}\).  
Figure 8 and Table 5 present the crack geometry and widths of the cracks that appeared on the surface of the wire mesh deck slab and SFRC deck slab after aging for seven days and 56 days. Figure 8a shows the crack geometry on the surface of the wire mesh and SFRC deck slabs after seven days of aging. At the beginning, cracks appeared on the surface of both the wire mesh and SFRC deck slabs due to plastic shrinkage. The average crack width is shown to be 0.1 mm, and the maximum crack width is 0.2 mm. Figure 8b shows the crack geometry on the surface of the wire mesh and SFRC deck slabs after 56 days of aging. After 56 days of aging, drying shrinkage cracks appeared on the entire surface of the wire mesh deck slab, with crack widths ranging from 0.1 to 0.5 mm. In the case of the SFRC deck slab, drying shrinkage cracks appeared at the same location as the initial cracks that were due to plastic shrinkage, with crack widths ranging from 0.1 to 0.3 mm. This comparison of the crack geometry and crack width in terms of aging indicates that the SFRC deck slab can inhibit plastic shrinkage cracks that occur early more effectively than the wire mesh deck slab can, and that the SFRC deck slab also is more effective than the wire mesh slab in controlling the number of drying shrinkage cracks and the crack widths.  
Figure 8: Crack geometry and crack widths after aging for wire mesh (WM) deck slabs and steel fiber-reinforced concrete (SFRC) deck slabs: (**a**) 7 days and (**b**) 56 days.  
Figure 7: Deck slab drying shrinkage strain during aging: (**a**) at surface and (**b**) at center of deck slab.