本文關鍵詞：鹽凍環(huán)境下混凝土構件耐久性及壽命預測研究　出處：《西安建筑科技大學》2014年博士論文　論文類型：學位論文

  更多相關文章： 粉煤灰混凝土 鹽凍損傷 氯離子侵蝕 銹蝕率 耐久性 壽命預測

【摘要】：鋼筋混凝土結構耐久性失效，會導致巨大的經(jīng)濟損失，影響社會經(jīng)濟發(fā)展。鹽凍損傷對混凝土材料產(chǎn)生的不可逆累積損傷，會加快環(huán)境中腐蝕介質的滲透與擴散，加速混凝土中鋼筋銹蝕與混凝土保護層銹脹開裂，影響混凝土結構的正常使用。研究鹽凍環(huán)境下混凝土耐久性，對新建混凝土結構工程耐久性設計和在役混凝土結構工程的耐久性評定及維護具有重要的理論意義和工程價值。 本文以除冰鹽環(huán)境與寒冷地區(qū)海洋環(huán)境中的鋼筋混凝土結構為研究對象，研究鹽凍損傷對混凝土耐久性的影響，預測鹽凍環(huán)境混凝土結構耐久性使用壽命，主要研究內容如下： （1）通過以3.5%NaCl溶液為凍融介質的粉煤灰混凝土快速鹽凍試驗，研究了鹽凍循環(huán)作用對混凝土損傷的影響規(guī)律，分析了鋼筋對混凝土鹽凍損傷變化的影響。研究了受鹽凍粉煤灰混凝土的靜彈性模量變化規(guī)律，建立了混凝土靜彈性模量與鹽凍損傷度的關系模型，為鹽凍環(huán)境鋼筋混凝土構件耐久性研究及承載性能評價奠定了基礎。 （2）開展了受鹽凍鋼筋混凝土構件氯離子擴散規(guī)律的試驗研究，，基于凍融作用對粉煤灰混凝土表層結構的影響，研究了鹽凍損傷對混凝土中自由氯離子擴散過程的影響規(guī)律，建立了氯離子擴散系數(shù)與鹽凍損傷度的關系模型。基于Fick第二定律，考慮鹽凍損傷對混凝土中氯離子擴散的影響，建立了鹽凍環(huán)境混凝土中氯離子擴散模型，并對建立的氯離子擴散模型進行了工程驗證。通過分析鋼筋對混凝土中氯離子擴散的阻滯效應，提出了鹽凍環(huán)境混凝土中鋼筋表面氯離子濃度計算方法。 （3）通過分析鹽凍環(huán)境混凝土中鋼筋銹蝕過程控制，考慮鹽凍損傷對混凝土中氯離子擴散及鋼筋銹蝕的影響，建立了鹽凍環(huán)境混凝土保護層銹脹開裂前鋼筋銹蝕速率預測模型，分析了各因素對混凝土保護層銹脹開裂前鋼筋銹蝕速率的影響規(guī)律，并對該預測模型進行了工程驗證。 （4）基于鹽凍環(huán)境混凝土保護層銹脹開裂加速試驗研究，分析了混凝土鹽凍損傷程度、混凝土保護層厚度與鋼筋直徑比值等因素對混凝土銹脹開裂形態(tài)、開裂時的鋼筋銹蝕率的影響。建立了鹽凍環(huán)境混凝土保護層銹脹開裂時鋼筋銹蝕率模型，為鹽凍環(huán)境下混凝土結構耐久性壽命預測提供了理論依據(jù)。 （5）開展了鹽凍環(huán)境銹蝕鋼筋混凝土結構耐久性壽命預測研究。通過分析混凝土凍融循環(huán)壽命與凍融循環(huán)疲勞作用的關系，得出混凝土凍融損傷壽命的概率分布特征，提出了實際凍融環(huán)境混凝土耐久性壽命預測方法。通過分析混凝土中鋼筋初始銹蝕條件、保護層銹脹開裂條件，基于可靠性理論提出了鹽凍環(huán)境中混凝土結構鋼筋初始銹蝕壽命預測方法與混凝土保護層銹脹開裂壽命預測方法，為混凝土結構耐久性設計提供了參考。
[Abstract]:Durability failure of reinforced concrete structures will lead to huge economic losses and impact on social and economic development. Salt freezing damage to concrete materials caused by irreversible cumulative damage. It will accelerate the permeation and diffusion of corrosive medium in the environment, accelerate the corrosion of steel bar in concrete and the corrosion cracking of concrete protective layer, and affect the normal use of concrete structure. The durability of concrete in salt frozen environment is studied. It has important theoretical significance and engineering value for durability design of new concrete structure engineering and durability evaluation and maintenance of existing concrete structure engineering. In this paper, the reinforced concrete structure in deicing salt environment and marine environment in cold area is taken as the research object, the influence of salt freezing damage on concrete durability is studied, and the durability service life of concrete structure in salt frozen environment is predicted. The main contents of the study are as follows: 1) through rapid salt freezing test of fly ash concrete with 3.5 NaCl solution as freeze-thawing medium, the effect of salt freezing cycle on concrete damage is studied. In this paper, the influence of reinforcement on the change of salt freezing damage of concrete is analyzed. The static elastic modulus of fly ash concrete subjected to salt freezing is studied, and the relation model between static elastic modulus of concrete and damage degree of salt freezing is established. It lays a foundation for durability research and load-bearing performance evaluation of reinforced concrete members in salt-frozen environment. (2) the experimental study on chloride ion diffusion of reinforced concrete members subjected to salt freezing is carried out. Based on the effect of freeze-thaw action on the surface structure of fly ash concrete. The influence of salt freezing damage on the free chloride diffusion process in concrete was studied, and the relationship model between chloride diffusion coefficient and salt freezing damage degree was established based on Fick's second law. Considering the effect of salt freezing damage on chloride diffusion in concrete, a chloride diffusion model in salt frozen concrete was established. Based on the analysis of the effect of reinforcing bar on chloride ion diffusion in concrete, the method of calculating chloride ion concentration on reinforced bar surface in salt frozen concrete is put forward. 3) through analyzing the process control of reinforcement corrosion in concrete in salt freezing environment, considering the influence of salt freezing damage on chloride ion diffusion and reinforcement corrosion in concrete. The prediction model of steel bar corrosion rate before corrosion expansion cracking of concrete cover in salt frozen environment was established, and the influence of various factors on steel bar corrosion rate before corrosion expansion and cracking of concrete cover layer was analyzed. The prediction model is verified by engineering. 4) based on the accelerated test of corrosion expansion cracking of concrete cover in salt freezing environment, the damage degree of concrete salt frost, the ratio of concrete cover thickness to diameter of steel bar and other factors on the form of corrosion cracking of concrete are analyzed. The model of corrosion rate of steel bar in salt frozen environment is established, which provides a theoretical basis for the durability life prediction of concrete structure under salt frozen environment. 5) the durability life prediction of corroded reinforced concrete structures in salt freezing environment is studied. The relationship between freeze-thaw cycle life and freeze-thaw cycle fatigue of concrete is analyzed. The probabilistic distribution characteristics of freeze-thaw damage life of concrete are obtained, and the prediction method of durability life of concrete in freezing and thawing environment is put forward. By analyzing the initial corrosion condition of steel bar in concrete, the condition of corrosion heaving and cracking of protective layer is analyzed. Based on the reliability theory, the prediction method of initial corrosion life of reinforced bars in salt frozen environment and the life prediction method of corrosion cracking of concrete cover are proposed, which provides a reference for the durability design of concrete structures.
【學位授予單位】：西安建筑科技大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TU375

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