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  本文關鍵詞： 混凝土 碳化 彎曲荷載 礦物摻合料 細觀層次 COMSOL Multiphysics　出處：《南京工業(yè)大學》2015年碩士論文　論文類型：學位論文

【摘要】：自上世紀70年代以來,大氣中的二氧化碳濃度逐年升高,混凝土碳化問題顯得愈加嚴重。同時現(xiàn)代混凝土大量摻入礦渣、粉煤灰等礦物摻合料,影響了混凝土的抗碳化性能。此外,服役中的混凝土工程結構往往伴隨著復雜的應力場作用,尤其是拉應力會導致混凝土孔隙乃至裂縫的擴展,這就加劇了二氧化碳在混凝土中的傳輸。因此,需要進一步考慮摻合料,荷載等因素對真實服役環(huán)境中混凝土碳化過程的影響。本文圍繞著含有兩種摻合料混凝土在碳化和靜力荷載耦合作用下的劣化過程和機理,揭示了摻合料對混凝土碳化深度、pH值、抗折強度的影響規(guī)律,同時分析了不同彎曲荷載應力對混凝土碳化深度的影響�；贔ick第二定律和質量守恒定律,提出了含有礦物摻合料混凝土在碳化和荷載耦合作用下的碳化模型,應用多物理場耦合有限元軟件COMSOL Multiphysics進行求解。最后還從細觀層次上研究了混凝土的碳化過程。主要研究內容和結果如下：(1)研究了單摻和雙摻混凝土的碳化深度和pH值的時變規(guī)律。研究結果表明：對于單摻粉煤灰的試件,其抗碳化性能與摻量成正比關系；而對于單摻礦渣的試件,礦渣含量為10%時,碳化深度達到最低值,然而當?shù)V渣含量達到40%時,其抗碳化能力大幅降低；對于雙摻試件,在任一摻合料取代率達到40%時,抗碳化能力有著顯著的降低；無論單摻還是雙摻混凝土,pH值演變規(guī)律和碳化深度值演變規(guī)律保持一致。(2)分析了彎曲應力水平作用下混凝土的碳化深度和pH值的時變規(guī)律。分析表明彎曲應力種類和水平對碳化深度和pH值有著顯著的影響：在一定應力范圍內,彎曲拉應力能顯著提高混凝土的碳化深度,而彎曲壓應力改善了混凝土的抗碳化能力；(3)考慮荷摻合料種類和含量、彎曲荷載應力水平等因素,基于前人的研究成果,提出了考慮荷載和摻合料因素的碳化反應模型,用有限元軟件COMSOL Multiphysics模擬了混凝土的碳化過程。(4)從混凝土細觀層次出發(fā),開發(fā)了二維圓形和多邊形隨機骨料結構,基于提出的碳化反應模型,從混凝土細觀層次分析了不同骨料含量、形狀和界面過渡區(qū)對碳化反應過程的影響。
[Abstract]:Since the last century since 70s, concentration of carbon dioxide in the atmosphere increased year by year, the problem becomes more and more serious. At the same time the concrete carbonization of modern concrete mixed with a large number of slag, fly ash and other mineral admixture, affecting the carbonation resistance of concrete. In addition, the construction of concrete structure in service is often accompanied by complex stress field, especially is the tensile stress will lead to concrete cracks and pore expansion, which is exacerbated by the transmission of carbon dioxide in concrete. Therefore, the need for further consideration of admixture, load factors such as serving the effect of concrete carbonization processes in the environment of reality. In this paper contains two kinds of admixtures in concrete carbonation and static load coupling effect the degradation process and mechanism, reveals the admixture of concrete carbonation depth, pH value, influence the flexural strength at the same time, analyzes the different bending load on the stress The effect of concrete carbonization depth. The Fick's second law and based on the mass conservation law, put forward with mineral admixture concrete in carbonation and load coupling carbonation model, coupling finite element software COMSOL Multiphysics application of multi physics field is solved. Finally, from the micro level of concrete carbonization process. The main research contents and the results are as follows: (1) change regularity of single or double mixture concrete carbonation depth and pH value. The results show that the specimen mixed with fly ash, the anti carbonation properties and content is proportional to the relationship; and for the specimens of slag, slag content is 10% the carbonation depth, reaching the lowest value when the slag content reaches 40%, the carbonation resistance is greatly reduced; the double doped specimen, aggregate replace rate reached 40% in either mixed, anti carbonization capability has a significantly reduced; No single or double mixture concrete admixture, pH value and the evolution of the carbonation depth value evolution is consistent. (2) analyzed the bending variation regularity of carbonation depth and pH concrete under horizontal force value. Analysis shows that the bending stress on the type and level of carbonation depth and pH values have a significant impact. In a certain range of stress, the bending tensile stress can significantly improve the carbonation depth of concrete, and the bending stress to improve the carbonation resistance of concrete; (3) Considering Bearing admixture types and content of bending load factors on stress level, based on the previous research results, proposed model considering the carbonation reaction load and admixture factors, the carbonation process of concrete is simulated with finite element software COMSOL Multiphysics. (4) starting from the concrete meso level, the development of two-dimensional circular and polygon random aggregate structure, based on the carbonization reaction The effect of different aggregate content, shape and interface transition zone on the carbonation process is analyzed from the concrete meso level.

【學位授予單位】：南京工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU528

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本文編號：1532353