Stress Development and Crack Monitoring of Massive Concrete Walls with Embedded Air-cooling Pipes

Thermal cracking is a severe problem faced with massive concrete structures especially in early ages. In order to control the temperature distribution and lower cracking risk of a large-dimension reinforced concrete wall during construction, air pipe cooling was applied to experimental concrete walls with embedded corrugated pipes. Three levels of inlet airflow velocity (about 4, 8, and 12 m/s) were studied and compared with the wall without pipe cooling. Temperature distribution and strain development were obtained with embedded sensors. Besides, surface crack depth development with age was monitored with the ultrasonic testing analyzer. Moreover, stress distributions were derived through thermomechanical analysis to illustrate the strain and cracking trend of concrete walls under the specific cooling scenarios as in the experiment. According to the results, cooling efficiency was closely related to pipe intervals. In the pipe-intensive region, air pipe cooling effectively reduced the peak temperature and concrete volumetric deformation. However, higher air velocity induced more considerable tensile stress both surrounding the pipe and on the outer surface in the region of larger pipe intervals. It indicates that the proper airflow velocity should be carefully investigated for the purpose of cracking control under a given pipe arrangement.