Papers by Keyword: Wet-Dry Cycles

Abstract: This study investigated the effect of rock-water interaction on microstructural properties of various weathering grade sandstone. Sandstone samples were acquired from the Sor-Range coal mine area, Pakistan, and were investigated using a tabletop scanning electron microscope (SEM). The characteristics of microstructures from micrographs were obtained using ImageJ software. According to the findings an increase in wet and dry cycles significantly affects the microstructures (pore spaces and microcracks). The porosity and microcracks density of sandstone increases with the number of wet and dry cycles. Furthermore, the length of microcracks increases as the weathering grade increases. As variation in rock macroscopic mechanical characteristics is directly associated with the deterioration of microstructures. Therefore, analyzing the effect of water-rock interaction in various weathering grades of rock can offer a more accurate reference index for assessing the stability of geotechnical structures.

Abstract: The bonded joints between CFRP and high strength concrete subjected to different wet-dry cycles and sustained loads were studied with double-lab shear tests. The results indicate that with the increase of cycles, the ultimate bond load rises at early stage, however decreases generally. Sustained loads significantly affect failure mode of specimens, and make the destruction more sudden.

Abstract: A review of current worldwide researches on the durability of concrete was presented. Porosity and water content of concrete changing in wet-dry cycles were introduced, the failure mechanism of freeze-thaw and carbonation and the relation with pore structure, as well as its interaction influencing factors. Some key problems to be further studied were proposed on the basis of the research achievements of leaching.

Abstract: Under immersed and we-dry cyclic conditions, the deterioration processes of the organic coating on carbon steel surface have been comparatively studied using electrochemical techniques. The wet-dry cycles were carried out by exposure to 4 h immersion and 4h dryness (4-4h cycles) and 12h immersion and 12h dryness (12-12h cycles) conditions, respectively. The immersion condition was carry out in a 3.5% NaCl solution and drying at 298K and 50% RH. According to the EIS characteristics, the entire deterioration processes under above three mentioned conditions can be divided into three main stages, consisting of the medium penetration, corrosion initiation and corrosion extension. Comparing with the immersed, the 4-4h wet-dry cycles greatly accelerated the entire deterioration process; especially during the corrosion initiation and the corrosion extension periods, leading the paint system lose its anti-corrosive performance in a short period. However, the 12-12h wet-dry cycles decelerated the entire deterioration process, prolonging the coatings anticorrosive ability. The acceleration mechanism of the coatings and underlying metal corrosion under wet-dry cycles was discussed based on the above results.