Fracture mechanics performance of self-consolidating concrete exposed to cryogenic temperatures

It is important not to be dependent on a single country in the procurement of natural gas that is one of the basic heating sources of today and that we import from other countries. Thus, the storage of natural gas at high volumes is very important. It is required to liquefy the natural gas in order to store it, and the volume of natural gas decreases by about 600 times during liquefaction, and the temperature of natural gas in liquid phase becomes -162oC. These low temperatures are being called cryogenic temperature. The concrete storage tanks are required to be resistant against thermal effects and unexpected leakages during filling and discharge. In this study, the effects possible to arise and the behavior of concrete as the result of contact of cryogenic liquid and concrete in cases of any leakage, thermal shock etc relevant to the concrete encased tanks –where the natural gas is being stored- was examined. Within this scope, high durable self-consolidating concrete design –whose usage may be suggested for concrete encased cryogenic storage tanks- was realized. In the study, the change in the strength properties as the result of one and five cycles freezing and thawing effect was examined by using liquid nitrogen in order to represent cryogenic effect. Moreover, in order to search the effect of humidity within concrete, the samples were subjected to two different curing operations as being in water and in air. Due to high strategic importance of energy structures, the strength parameters of designed concretes were determined by two parameter fracture mechanics test method as well as traditional strength criteria. In order to determine the parameters of fracture mechanics, beams of three different sizes having three different notch lengths for each size were produced. Mechanical tests were performed on the produced beams. The results were obtained by associating the obtained data with the traditional design methods and parameters of fracture mechanics. Consequently, it was determined that samples of air curing were more resistant to cryogenic cycle than the samples of water curing. Following one cycle of cryogenic operation, the KIC and CTODc values had showed an increase. And as the result of five cycles, a decrease was observed in the KIC and CTODc values compared to one cycle. Key Words: Cryogenic Temperature, Fracture Mechanics, Natural Gas, Self-Consolidating Concrete