Research On Hydraulic Concrete Frost Resistance Durability Of Major Water Supply Project In Cold Region

Our country is vast in territory, the northern region most in the cold zone, many ofthe major water supply projects are building in the Northeast China. During theconstruction and use in complete, partial concrete have different degrees of freeze-thawdamage or large area concrete freeze-thaw damage or frost cracking, thus resulting inconcrete compressive strength, tension strength, elastic modulus and other relatedmechanical properties greatly decreased, eventually even some dam project in operationafter a dozen years, had to be scrapped. The paper investigated and studied the freezethawing mechanism and the research result of the hydraulic concrete frost durability,cleared hydraulic concrete freeze-thaw failure mechanism, and determined the factorsaffecting the effect of hydraulic concrete frost resistance, to provide the correspondingtheoretical basis for this study. At first the paper do the freeze-thaw cycle experiment onstrength grade of C25for hydraulic concrete in freeze-thaw temperature varies in therange of8±2oC～-17±2oC；the second, for the frost resistance durability of hydraulicconcrete in cold area, the test was set to the freeze-thaw temperature change range from8±2oC～-22±2oC;at last, through applying the size of0.1fttensile stress on strengthgrade of C35for hydraulic concrete, freezing thawing test was conducted in thecontinuous load state. The main works and conclusions are as follows:(1) Through the freeze-thaw cycle experiment on strength grade of C25forhydraulic concrete in freeze-thaw temperature varies in the range of8±2oC～-17±2oC,the paper measured and analyzed the mass loss, relative dynamic elastic modulus of thecompressive strength and flexural strength of the change rule and the reasons under theconditions of hydraulic concrete freeze-thaw cycle. Experimental results show that whenthe reference to the hydraulic design of concrete regulation (DL/T5330-5330) tocalculate the hydraulic concrete mix proportion has good frost resistance.(2) For the frost resistance durability of hydraulic concrete in cold area, the test wasset to the freeze-thaw temperature change range from8±2oC～-22±2oC, and thencompared and analyzed the result with the standard quick freezing method. The resultsshowed that the lowest freezing temperatures on effects of freezing thawing damage ofconcrete was very important, the relevant mechanical properties of block under the standard quick freezing method could not accurately reflect the frost resistance ofhydraulic concrete.(3) Through applying the size of0.1fttensile stress on strength grade of C35forhydraulic concrete, freezing thawing test was conducted in the continuous load state.Obviously pre-tensioning weaken the antifreeze performance of concrete specimen,antifreeze label F200that do not meet the design.