硫酸盐腐蚀和冻融复合作用下混凝土的性能研究
发布时间：2019-06-17 21:47
【摘要】：硫酸盐侵蚀和冻害均是导致混凝土耐久性退化的重要环境因素。混凝土在遭受硫酸盐侵蚀与冻融循环共同作用时,对混凝土会产生较单一因素劣化作用更严重的破坏。因此,系统地开展硫酸盐侵蚀与冻融循环复合因素作用下的混凝土耐久性研究,解释混凝土受硫酸盐侵蚀与冻融循环复合作用劣化机理,对提升相应环境下的混凝土的耐久性设计和寿命预测具有重要意义。针对以上问题,本文研究了在硫酸盐侵蚀环境下水灰比、含气量等内部因素和冻融条件等外部因素对混凝土力学性能和变形的影响,并开展了孔溶液分析和微观试验研究,探究硫酸盐腐蚀和冻融复合条件下混凝土的微结构劣化及硫酸根离子传输机理。主要研究内容和成果如下:(1)试验研究了混凝土试块在硫酸盐腐蚀和冻融循环复合条件下的力学性能规律。当混凝土受到冻融破坏和硫酸盐侵蚀共同作用时,两种劣化因素相互促进,会产生超叠加效应,比一般混凝土冻融破坏严重得多。5%硫酸钠盐冻与5%硫酸镁盐冻相比,会对混凝土造成更严重的损伤,造成这种现象主要与破坏的类型有关:5%硫酸钠除了对混凝土有化学侵蚀作用,还会对混凝土产生盐结晶物理破坏,后者是造成5%硫酸钠盐冻破坏的主因,5%硫酸镁对混凝土的破坏主要是化学侵蚀,盐结晶造成的物理破坏不如5%硫酸钠的盐冻破坏明显。(2)试验研究了混凝土试块在硫酸盐腐蚀和冻融循环复合条件下的变形发展规律。在质量分数5%的硫酸钠溶液、5%的硫酸镁溶液和水中,对引气和未引气的混凝土试块进行快速冻融,同时在5%硫酸钠溶液和5%硫酸镁溶液中浸泡混凝土试块以进行对比,在此过程中采用静态应变仪测量试块的应变发展规律。研究结果表明,在1200min的时间里,引气的混凝土要比未引气的混凝土应变增长量大一倍。在硫酸钠溶液冻融条件下的试块应变增长最快,破坏最显著,其后依次是水中冻融、硫酸镁溶液冻融、硫酸钠溶液浸泡和硫酸镁溶液浸泡等条件下的试块。(3)混凝土加入引气剂后,将会改变混凝土内部的孔结构,使气泡孔增多,内部密实度下降,因此会导致混凝土的初始强度降低,但是,气泡孔对混凝土的抗冻性却起到促进的作用,当混凝土受冻融循环的作用时,它可以缓冲来自毛细孔结冰带来的渗透压,是混凝土不至于被渗透压破坏,另外它还切断了连通孔的通道,阻止硫酸盐的侵入,进而提高了混凝土的抗腐蚀性。(4)冻融条件下能加快SO42-向混凝土内部迁移传输,使混凝土遭受破坏;SO42-在混凝土内部发生化学反应,和水泥石发生反应,生成具有膨胀性的物质,主要为钙矾石和石膏;不同硫酸盐溶液对混凝土的化学反应不同,硫酸镁对混凝土的腐蚀作用要小于硫酸钠;水灰比越大,混凝土内部连通孔越多,混凝土内部越稀疏,进入混凝土内部的硫酸根离子越多;混凝土内部加入引气能提高混凝土的耐久性。
[Abstract]:Sulfate attack and freezing damage are important environmental factors that lead to the deterioration of the durability of concrete. When the concrete is subjected to the joint action of the sulfate attack and the freeze-thaw cycle, the concrete can cause more serious damage to the deterioration of the single factor. Therefore, it is of great significance to study the durability of concrete under the action of sulfate attack and freeze-thaw cycle, and to explain the degradation mechanism of the composite effect of sulfate attack and freeze-thaw cycle, which is of great significance to the durability design and life prediction of the concrete under the corresponding environment. In view of the above problems, this paper studies the effect of external factors such as water-cement ratio, gas content and other factors on the mechanical properties and deformation of concrete under the environment of sulfate attack, and studies the hole solution analysis and micro-test. To investigate the microstructure and sulfate ion transport mechanism of concrete under the conditions of sulfate corrosion and freeze-thaw composite. The main contents and results are as follows: (1) The mechanical properties of the concrete test block under the combined conditions of sulfate corrosion and freeze-thaw cycle are studied. when the concrete is combined with the freeze-thaw damage and the sulfate attack, the two degradation factors are mutually reinforcing, and the super-superposition effect can be generated, which is more severe than that of the general concrete freeze-thaw damage, and the 5% sodium sulfate salt freeze can cause more serious damage to the concrete compared with the 5% magnesium sulfate salt freeze, This phenomenon is mainly related to the type of destruction:5% sodium sulfate, in addition to the chemical erosion of the concrete, also has physical destruction to the concrete, which is the main cause of the salt freeze damage of 5% sodium sulfate, and the destruction of the concrete by 5% magnesium sulfate is mainly chemical attack, The physical destruction caused by salt crystallization is not as evident as the salt freeze of 5% sodium sulfate. (2) The deformation and development of concrete test block under the combined conditions of sulfate corrosion and freeze-thaw cycle are studied. a 5% sodium sulfate solution,5% magnesium sulfate solution, and water were subjected to a rapid freeze-thaw on the air and air-free concrete blocks, while the concrete blocks were soaked in 5% sodium sulfate solution and 5% magnesium sulfate solution for comparison, In this process, static strain gauge is used to measure the strain development of the test block. The results show that in the time of 1200 min, the air-entraining concrete is much more than that of the non-air-entrained concrete. The strain of the test block under the freezing and thawing condition of the sodium sulfate solution is the fastest, the damage is the most significant, and the test block is sequentially subjected to freeze-thaw in water, freeze-thaw of the magnesium sulfate solution, immersion of the sodium sulfate solution, and immersion of the magnesium sulfate solution. (3) After the concrete is added into the air entraining agent, the hole structure inside the concrete is changed, the air bubble hole is increased, the internal compactness is reduced, the initial strength of the concrete is reduced, When the concrete is subjected to freeze-thaw cycling, the concrete can buffer the osmotic pressure from the freezing of the capillary pores, so that the concrete is not damaged by the osmotic pressure, and the channel of the communication hole is also cut off, so that the intrusion of the sulfate is prevented, and the corrosion resistance of the concrete is further improved. (4) the freezing and thawing condition can accelerate the transport of the SO42-to the inside of the concrete to cause the concrete to be damaged; the SO42-reacts with the cement stone inside the concrete to generate the material with the expansibility, mainly the alunite and the gypsum; The chemical reaction of different sulfate solutions to the concrete is different, the corrosion of the magnesium sulfate to the concrete is less than the sodium sulfate, the larger the water-cement ratio, the more the internal communication holes in the concrete, the more sparse the inside of the concrete, and the more sulfate ions in the interior of the concrete; The addition of air-entraining in the concrete can improve the durability of the concrete.
【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
本文编号：2501287
[Abstract]:Sulfate attack and freezing damage are important environmental factors that lead to the deterioration of the durability of concrete. When the concrete is subjected to the joint action of the sulfate attack and the freeze-thaw cycle, the concrete can cause more serious damage to the deterioration of the single factor. Therefore, it is of great significance to study the durability of concrete under the action of sulfate attack and freeze-thaw cycle, and to explain the degradation mechanism of the composite effect of sulfate attack and freeze-thaw cycle, which is of great significance to the durability design and life prediction of the concrete under the corresponding environment. In view of the above problems, this paper studies the effect of external factors such as water-cement ratio, gas content and other factors on the mechanical properties and deformation of concrete under the environment of sulfate attack, and studies the hole solution analysis and micro-test. To investigate the microstructure and sulfate ion transport mechanism of concrete under the conditions of sulfate corrosion and freeze-thaw composite. The main contents and results are as follows: (1) The mechanical properties of the concrete test block under the combined conditions of sulfate corrosion and freeze-thaw cycle are studied. when the concrete is combined with the freeze-thaw damage and the sulfate attack, the two degradation factors are mutually reinforcing, and the super-superposition effect can be generated, which is more severe than that of the general concrete freeze-thaw damage, and the 5% sodium sulfate salt freeze can cause more serious damage to the concrete compared with the 5% magnesium sulfate salt freeze, This phenomenon is mainly related to the type of destruction:5% sodium sulfate, in addition to the chemical erosion of the concrete, also has physical destruction to the concrete, which is the main cause of the salt freeze damage of 5% sodium sulfate, and the destruction of the concrete by 5% magnesium sulfate is mainly chemical attack, The physical destruction caused by salt crystallization is not as evident as the salt freeze of 5% sodium sulfate. (2) The deformation and development of concrete test block under the combined conditions of sulfate corrosion and freeze-thaw cycle are studied. a 5% sodium sulfate solution,5% magnesium sulfate solution, and water were subjected to a rapid freeze-thaw on the air and air-free concrete blocks, while the concrete blocks were soaked in 5% sodium sulfate solution and 5% magnesium sulfate solution for comparison, In this process, static strain gauge is used to measure the strain development of the test block. The results show that in the time of 1200 min, the air-entraining concrete is much more than that of the non-air-entrained concrete. The strain of the test block under the freezing and thawing condition of the sodium sulfate solution is the fastest, the damage is the most significant, and the test block is sequentially subjected to freeze-thaw in water, freeze-thaw of the magnesium sulfate solution, immersion of the sodium sulfate solution, and immersion of the magnesium sulfate solution. (3) After the concrete is added into the air entraining agent, the hole structure inside the concrete is changed, the air bubble hole is increased, the internal compactness is reduced, the initial strength of the concrete is reduced, When the concrete is subjected to freeze-thaw cycling, the concrete can buffer the osmotic pressure from the freezing of the capillary pores, so that the concrete is not damaged by the osmotic pressure, and the channel of the communication hole is also cut off, so that the intrusion of the sulfate is prevented, and the corrosion resistance of the concrete is further improved. (4) the freezing and thawing condition can accelerate the transport of the SO42-to the inside of the concrete to cause the concrete to be damaged; the SO42-reacts with the cement stone inside the concrete to generate the material with the expansibility, mainly the alunite and the gypsum; The chemical reaction of different sulfate solutions to the concrete is different, the corrosion of the magnesium sulfate to the concrete is less than the sodium sulfate, the larger the water-cement ratio, the more the internal communication holes in the concrete, the more sparse the inside of the concrete, and the more sulfate ions in the interior of the concrete; The addition of air-entraining in the concrete can improve the durability of the concrete.
【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
【引证文献】
相关期刊论文 前1条
1 王柳;;冻融与腐蚀复合作用下煤矸石喷射混凝土耐久性演化规律[J];铁道建筑;2017年01期
，本文编号：2501287
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