硫酸鹽腐蝕和凍融復(fù)合作用下混凝土的性能研究
發(fā)布時間：2019-06-17 21:47
【摘要】：硫酸鹽侵蝕和凍害均是導(dǎo)致混凝土耐久性退化的重要環(huán)境因素�；炷猎谠馐芰蛩猁}侵蝕與凍融循環(huán)共同作用時,對混凝土?xí)a(chǎn)生較單一因素劣化作用更嚴(yán)重的破壞。因此,系統(tǒng)地開展硫酸鹽侵蝕與凍融循環(huán)復(fù)合因素作用下的混凝土耐久性研究,解釋混凝土受硫酸鹽侵蝕與凍融循環(huán)復(fù)合作用劣化機(jī)理,對提升相應(yīng)環(huán)境下的混凝土的耐久性設(shè)計和壽命預(yù)測具有重要意義。針對以上問題,本文研究了在硫酸鹽侵蝕環(huán)境下水灰比、含氣量等內(nèi)部因素和凍融條件等外部因素對混凝土力學(xué)性能和變形的影響,并開展了孔溶液分析和微觀試驗研究,探究硫酸鹽腐蝕和凍融復(fù)合條件下混凝土的微結(jié)構(gòu)劣化及硫酸根離子傳輸機(jī)理。主要研究內(nèi)容和成果如下:(1)試驗研究了混凝土試塊在硫酸鹽腐蝕和凍融循環(huán)復(fù)合條件下的力學(xué)性能規(guī)律。當(dāng)混凝土受到凍融破壞和硫酸鹽侵蝕共同作用時,兩種劣化因素相互促進(jìn),會產(chǎn)生超疊加效應(yīng),比一般混凝土凍融破壞嚴(yán)重得多。5%硫酸鈉鹽凍與5%硫酸鎂鹽凍相比,會對混凝土造成更嚴(yán)重的損傷,造成這種現(xiàn)象主要與破壞的類型有關(guān):5%硫酸鈉除了對混凝土有化學(xué)侵蝕作用,還會對混凝土產(chǎn)生鹽結(jié)晶物理破壞,后者是造成5%硫酸鈉鹽凍破壞的主因,5%硫酸鎂對混凝土的破壞主要是化學(xué)侵蝕,鹽結(jié)晶造成的物理破壞不如5%硫酸鈉的鹽凍破壞明顯。(2)試驗研究了混凝土試塊在硫酸鹽腐蝕和凍融循環(huán)復(fù)合條件下的變形發(fā)展規(guī)律。在質(zhì)量分?jǐn)?shù)5%的硫酸鈉溶液、5%的硫酸鎂溶液和水中,對引氣和未引氣的混凝土試塊進(jìn)行快速凍融,同時在5%硫酸鈉溶液和5%硫酸鎂溶液中浸泡混凝土試塊以進(jìn)行對比,在此過程中采用靜態(tài)應(yīng)變儀測量試塊的應(yīng)變發(fā)展規(guī)律。研究結(jié)果表明,在1200min的時間里,引氣的混凝土要比未引氣的混凝土應(yīng)變增長量大一倍。在硫酸鈉溶液凍融條件下的試塊應(yīng)變增長最快,破壞最顯著,其后依次是水中凍融、硫酸鎂溶液凍融、硫酸鈉溶液浸泡和硫酸鎂溶液浸泡等條件下的試塊。(3)混凝土加入引氣劑后,將會改變混凝土內(nèi)部的孔結(jié)構(gòu),使氣泡孔增多,內(nèi)部密實度下降,因此會導(dǎo)致混凝土的初始強度降低,但是,氣泡孔對混凝土的抗凍性卻起到促進(jìn)的作用,當(dāng)混凝土受凍融循環(huán)的作用時,它可以緩沖來自毛細(xì)孔結(jié)冰帶來的滲透壓,是混凝土不至于被滲透壓破壞,另外它還切斷了連通孔的通道,阻止硫酸鹽的侵入,進(jìn)而提高了混凝土的抗腐蝕性。(4)凍融條件下能加快SO42-向混凝土內(nèi)部遷移傳輸,使混凝土遭受破壞;SO42-在混凝土內(nèi)部發(fā)生化學(xué)反應(yīng),和水泥石發(fā)生反應(yīng),生成具有膨脹性的物質(zhì),主要為鈣礬石和石膏;不同硫酸鹽溶液對混凝土的化學(xué)反應(yīng)不同,硫酸鎂對混凝土的腐蝕作用要小于硫酸鈉;水灰比越大,混凝土內(nèi)部連通孔越多,混凝土內(nèi)部越稀疏,進(jìn)入混凝土內(nèi)部的硫酸根離子越多;混凝土內(nèi)部加入引氣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.
【學(xué)位授予單位】：青島理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU528
本文編號：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.
【學(xué)位授予單位】：青島理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU528
【引證文獻(xiàn)】
相關(guān)期刊論文 前1條
1 王柳;;凍融與腐蝕復(fù)合作用下煤矸石噴射混凝土耐久性演化規(guī)律[J];鐵道建筑;2017年01期
，本文編號：2501287
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