## 4 Conclusions  
In this study, eight full-scale CRTS III concrete base plates were constructed, instrumented, and subjected to different curing regimes in order to investigate the effects of environmental boundary conditions on the early transverse cracking behavior of the base plate. In-situ variations of strain, temperature, and cracking of these concrete plates were monitored for 150 days. A numerical procedure was developed to simulate the temperature-induced and humidity-induced stresses in these concrete base plates. The findings point to the following conclusions:  
1. Based on in-site strain monitoring made at the desired positions, the embedded strain gauges can provide an indication of when cracks occurred. A precise determination of the time of cracking in the field base plates can be achieved by monitoring the change of strain rate. The detected crack-occurred positions fit well with the positions of the cracks visually observed. Generally, transverse cracks originated from the plate edge on both sides of the plate and propagated toward the plate's center.
2. Field inspections indicate that the early transverse cracks are quite susceptible to the curing conditions. A shorter sealed curing period will result in the earlier rise of transverse cracks and worse crack patterns. Inadequate curing will increase the number of cracks or, to be more specific, cause transverse cracks to occur at close spacings because a surface crack affects the surrounding area only at a limited distance.
3. The numerical results indicate that drying induced stress is the leading cause of the transverse cracks in the CRTS III base plate, since the calculated shrinkage stress at the time of plate edge cracking is much larger than the calculated temperature stress at the same time. Extending sealed curing to 45 or 120 days can significantly reduce the number of cracks and delay the time to cracking but will not effectively moderate drying shrinkage stress. Therefore, in order to eliminate cracking tendency, curing compounds and long-term curing should be required in practical engineering.  
Figure 16: Calculated humidity-induced longitudinal stresses at positions Edge-top, Edge-middle, and Edge-bottom: (**a**) Series I, (**b**) Series II, and (**c**) Series III and IV.  
**Author Contributions:** Conceptualization, Y.W.; methodology, Y.W.; validation, W.G.; investigation, W.G., L.Z. and X.H.; resources, Y.W.; writing--original draft preparation, W.G.; writing--review and editing, Y.W.; visualization, L.Z. and X.H.; supervision, Y.W.; funding acquisition, Y.W. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by National Natural Science Foundation of China (NSFC) under grant number of 52078273.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data is contained within the article.  
**Acknowledgments:** The authors are thankful for the funding provided by the National Natural Science Foundation of China (NSFC) under grant number 52078273.  
**Conflicts of Interest:** The authors declare that they have no conflict of interest.