Study On The Degradation Law Of Frost-resisting Durability About Hydraulic Concrete Materials

There are many large-scale salty soil zones in the cold and dry irrigation areas of northwestern China, where concrete buildings have been mainly suffering freeze-thaw damage for the lower ambient temperature, and they also being eroded by the harmful salt ions existing in salty soil. While with the global warming, carbon dioxide level in the air is in an upward trend, the buildings are affected by carbonation at the same time. Coupling effect of these multiple factors exacerbates the attenuation of concrete durability.So far, the literatures about antifreeze durability of concrete under multiple factors are not only relative fewer but shallow and less systematic. Therefore, it has practical significance to study the attenuation of concrete antifreeze durability in depth.In allusion to the problem of concrete buildings in Northwest appear insufficient antifreeze durability such as early cracking, spalling,combined “Supported by Program for Science & Technology Innovation Talents in Universities of Henan Province” of “Durability study of hydraulic concrete structures based on multi-field coupling in irrigation areas”, this topic takes the concrete buildings in Jingtaichuan Electrical-Irrigation District in Gansu Province(hereinafter short for “JID”) as the typical research object to study the antifreeze durability of concrete buildings in northwestern China. The site investigation, indoor accelerated test, theoretical analysis and evaluation method of concrete durability affected by multiple factors are primarily used to study the attenuation laws of concrete durability under the action of multiple field coupling. The main contents are as follows:(1) The major media and factors impacting concrete durability have been dowsed through the test analysis erosion samples of water and soil token from site and analysis the concrete residue by the X-ray diffractometer, dowsing the main erosion.(2) According to the concrete composition commonly used in JID, contrasting with other tow concrete compositions of cement replaced by fly ash or slag as the equivalent replacement method, the impact on the concrete antifreeze durability of salt solution with different concentration and different carbonization time was studied in consideration of freeze-thaw cycling of water, salt, and after carbonization,getting the durability laws of relative dynamic elastic modulus and mass in various operating conditions.(3) The gray correlation method was adopted to analyze the correlation of influencing factors on the concrete durability, and then use the conditional information entropy method based on rough set theory to calculate the weight of each factor impacting the relative dynamic elastic modulus and mass of concrete. Get the following main conclusions:(1) The order of correlation coefficient between the influence factors and the relative dynamic elastic modulus loss rate(mass loss rate)is Dosage of fly ash> Carbonization time> Dosage of mineral powder>Sulfate concentration;(2) The weight of each factor impact the relative dynamic elastic modulus is: Dosage of fly ash(0.297)> Carbonization time(0.266)> Dosage of mineral powder(0.262) >Sulfate concentration(0.175); For the mass loss rate: Dosage of fly ash(0.318)> Carbonization time(0.275)> Dosage of mineral powder(0.235)>Sulfate concentration(0.172).Through designing scientific and reasonable freeze-thaw cycle system, test methods for durability, the effect laws of different factors on the antifreeze durability attenuation of concrete has been studied, and the effect size of each factor had been obtained.