Authors: Xiao Yong Li, Zhi Gang Zhang
Abstract: The Impact of Corrosion on the Mechanical Properties of Smooth Steel Rebar HPB235 The impact of corrosion on the mechanical properties of steel rebar was examined. An experimental investigation was carried out in order to gain better insight of the effect of corrosion on the mass loss, strength, of smooth Steel Rebar HPB235 10 mm diameter steel bars that were artificially corroded for different corrosion levels. Corrosion is a negative contributor on the structural integrity of concrete structures and leads to degradation of the mechanical properties of steel rebar. In order to evaluate the influence of corrosion on the mechanical properties of steel rebar, an experimental investigation was conducted on smooth steel rebar of 10 mm diameters, and which were artificially corroded for 1, 3, 5 and 7 months. The laboratory tests suggest that corrosion duration had a significant impact on the strength degradation of the specimens. The mechanical properties of tensile test before and after corrosion indicated progressive variation and drastic drop in their values. The corrosion enhanced the damage and created pits and notches, resulting in stress concentration points and progressive reduction of strength. It gets the express formula nominal ultimate strength and nominal yield strength.
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Authors: Jian Fen Liu, Xing Nan Zhang, Hui Min Wang
Abstract: Many drought and flood indices have been developed, the Standardized Precipitation Index (SPI) is one which has various temporal scales together to form an overall judgment of drought and flood and can be applied easily to different locations to identify and monitor drought and flood. Take Nanjing, China in the study as an example to analysis drought and flood variation by computing SPI values of four time scales including 3-months, 6-months, 12-months and 24-months, applying precipitation data from 1946-2000 of the study area. The results demonstrated SPI can be appropriate to analyze drought and flood variation of Nanjing, while the precipitation data were divided into three stages(1946-1963,1964-1981,1982-2000), the frequencies of various drought and flood classes from various time scales are different, particularly 12-months and 24-months. The time series is longer, the frequencies are more reliable and the differences more little.
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Authors: Pavel Padevět, Petr Bittnar
Abstract: The article solves the comparing of the resize of cement paste creep with addition of fly ash in time. Creep was observed in the one monthly measurement for 4 and 10 months. The cement paste was prepared with fly ash in the ratio of the components 60/40 in favor of the cement components. Development of basic creep and creep was observed in water-saturated material. The measurement results are used as input data for the simulation of creep by the mathematical model and determine the values of the creep coefficient of cement paste. Results and comparison of q coefficients are presented.
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Authors: Konstantinos Sotiriadis, Sotirios Tsivilis, Vít Petranek
Abstract: The chloride diffusion in limestone cement concrete exposed to combined chloride and sulfate solutions at low temperature was studied. For this purpose, a normal Portland cement and two Portland limestone cements (15% and 35% w/w limestone content) were used for concrete preparation. The specimens were immersed in two combined chloride-sulfate solutions of different sulfate content, and stored at 5°C. The total and free chloride contents, as well as the chloride diffusion coefficients were determined for each concrete composition. The results show that the total chloride content and free to total chloride ratio are increased with time. The sulfate content of the corrosive solutions has not a clear effect on total chloride content and chloride diffusion coefficient. It seems that the lower sulfate content results, in general, in higher free to total chloride ratio values. The use of limestone in cement results in higher chloride concentrations in concrete and free to total chloride ratio values. In general, these phenomena are intensified for higher limestone content.
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