The Influence Of Heat Sulfate Solution To Mechanics Performance Of Concrete

This article takes the concrete durability research project of Gaoligong mountains tunnel in Dali-Ruili railway as the research background, and to investigate the effects of hyperpyrexia sulfate fluid on mechanic property of concrete. And the analysis is respectively from three aspects, which includes the orthogonal factor analysis of concrete after high sulfate solution soak and corrosion、the macro impact of concrete after corrosion (apparent performance, quality change, cube compressive strength, flexural strength, prism compressive strength, stress strain curve) and the micro performance.1、Orthogonal factor analysisFrom the range and variance analysis, we can get that the high temperature plays the most significant corrosive effect on the concrete specimens in the whole process of corrosion, and compared to immerse way, the concentration is slightly prominent in the early stage of the corrosion, but in the late corrosion, the significant effect of immersion way is more than the effect of concentration.2、Macroscopic aspectUnder the soak and corrosion of hyperpyrexia sulfate fluid, the concrete test sample cure 28d,56d,84d,112d and 140d respectively, through horizontal and vertical comparative analysis of different factors affecting the quality of concrete test sample, such as superficial phenomenon quality change、compressive strength、flexural strength compressive strength of the prismatic specimens and the stress strain curve, we can get:(1) Throughout the age, the concrete specimens compressive strength, flexural strength, and the prism compressive strength are broadly in line with law, through horizontal comparison (under different curing age), we can obtain that the concrete compressive strength indicates a trend of increasing first and then decreasing,112 days is the turning point of strength changes. And under different temperatures, the strength of the sample suffers decline of sulfate erosion in late, but under the condition of 80℃, the various strength loss rate are higher than 50℃、20℃. It shows that the higher the temperature, the larger the extent of intensity decrease and the more serious erosion by sulfate.(2) Compared to the compressive strength soaking in the clean water (0% concentration), the compressive strength in concentration of 2.5% and 5%, reduced 5.4% and 9.2% at 20℃ reductions reached 14.6% and 14.6% respectively at 80℃, which indicated that in the interaction effect of temperature and concentration, from the point of the rate of change of compressive strength, the temperature plays a positive role in promoting concentration, and accelerates the sulfate erosion for concrete.(3) In comparison to the stress strain with room temperature sulfate corrosion effect, it found that the stress strain curve of the highest point of H8 (80℃) is leaning right and on the low side, H8 has smaller elastic modulus, which shows that high temperature promoted the sulfate reaction, lowered the elastic modulus of the specimens and reduced the compressive strength.3、Microscopic aspectSelecting typical experimental specimens group for differential thermal analysis test, the test results analysis shows:under the sulfate erosion, the hydration products Ca(OH)2 of concrete under high temperature and curing are more than the consumption of than under the normal temperature curing, and with its reaction with and,the generated amount of corrosion products such as ettringite、gypsum etc. are also more than that under the normal temperature curing. This explains that the high temperature promoted the corrosion reaction, increased sulfate erosion for concrete. Through the longitudinal comparison of ages DTA learned:as the growth of the age, the concrete under sulfate corrosion effect becomes stronger and stronger.