Investigation of direct tension cracking and leakage in RC elements

A study is carried out to investigate the cracking characteristics and liquid tightness of a reinforced concrete element under direct tensile loads. The findings are directly applicable to environmental structures such as liquid containing tanks, the design of which is based on serviceability limit states. Cracking plays a significant role in durability and functionality of these types of structures. Contrary to the current practice in some design codes, pure tension cracks are more detrimental to the serviceability of the structure than other types of cracks and must be treated more cautiously. This study targets this issue both experimentally and analytically. Accordingly, a reinforced concrete specimen representing an element of a tank wall is subjected to a monotonic increasing direct tensile load and its cracking behavior is closely monitored. The influence of direct tension cracks on water tightness of the specimen is examined by exposing a major crack to pressurized water and evaluating the water leakage. Additionally, the water leakage flow rate is monitored over a period of 30 h to investigate any probable early self-healing capability of the cracked concrete. In the analytical phase, the load at cracking and the strain of the steel reinforcement are determined and compared with experimental test data. The accuracy of crack prediction models, namely, Broms and Lutz model, and a modified version of Gilbert model are assessed by comparing their results for crack spacing and the maximum crack width against those obtained from the experiment.