【摘要】：水泥混凝土的碳化反應(yīng)是指大氣中的CO2通過(guò)混凝土的孔隙或裂縫進(jìn)入溶解于孔溶液中與混凝土的氫氧化鈣、C-S-H凝膠、鈣礬石等物相發(fā)生中性化反應(yīng)�；炷恋闹行曰磻�(yīng)會(huì)引起水泥石的收縮,產(chǎn)生裂縫.導(dǎo)致混凝土的劣化,縮短混凝土的服役壽命。碳化反應(yīng)會(huì)引起混凝土內(nèi)部微結(jié)構(gòu)的變化,同時(shí)混凝上各種微結(jié)構(gòu)特征也會(huì)對(duì)碳化過(guò)程產(chǎn)生不同影響�；炷恋奈⒔Y(jié)構(gòu)主要包含其物相組成、孔隙率、孔徑分布等,可以分為界面過(guò)渡區(qū)和基體兩部分。界面過(guò)渡區(qū)是混凝土的薄弱環(huán)節(jié),界面過(guò)渡區(qū)及其微結(jié)構(gòu)對(duì)其傳輸性能和耐久性有重要影響。界面過(guò)渡區(qū)及其微結(jié)構(gòu)也必然是影響混凝土碳化過(guò)程的一個(gè)重要方面,能夠?yàn)榻⒖紤]界面影響的混凝土碳化模型提供依據(jù)。本文主要以界面碳化深度測(cè)試,納米力學(xué)性能表征碳化前后界面過(guò)渡區(qū)微結(jié)構(gòu),使用背散射(BSE)圖像分析技術(shù)研究界面過(guò)渡區(qū)微結(jié)構(gòu)在碳化前后的演變規(guī)律,以及界面特征的改變對(duì)混凝土抗碳化性能的影響四個(gè)方面研究了集料-基體界面對(duì)水泥混凝土碳化過(guò)程的影響。由于界面過(guò)渡區(qū)與基體的微結(jié)構(gòu)存在差別,碳化過(guò)程中必定會(huì)出現(xiàn)不同的碳化現(xiàn)象。界面過(guò)渡區(qū)具有孔隙率大、結(jié)構(gòu)疏松,氫氧化鈣含量較多且呈定向分布,未水化水泥含量較低等特征,使得界面的碳化速率快于基體。本文設(shè)計(jì)了規(guī)則形狀的集料.基體界面碳化試驗(yàn),成型了水膠比為0.60,0.53和0.35的含石灰石和花崗巖石片(作為集料)的凈漿試件,把試件兩端作為碳化面碳化28d,用酚酞法測(cè)量了界面與基體的碳化深度。實(shí)驗(yàn)結(jié)果表明：界面的碳化深度是基體的2-3倍,并且在碳化界面效應(yīng)的影響下,碳化曲線在界面附近形成-個(gè)具有距離界面越近碳化深度越深的特征的曲線。因此,CO2在界面?zhèn)鬏斔俣仁腔膫鬏斔俣鹊臄?shù)倍,界面?zhèn)鬏斒切纬刹糠痔蓟瘏^(qū)的原因之一。在此基礎(chǔ)上本文提出了考慮ITZ影響的水泥基材料碳化的物理模型。納米壓痕技術(shù)能夠測(cè)試界面過(guò)渡區(qū)納米力學(xué)性能,表征界面過(guò)渡區(qū)微結(jié)構(gòu),從而揭示碳化前后界面過(guò)渡區(qū)微結(jié)構(gòu)的演變規(guī)律。本文設(shè)計(jì)了不同水膠比的模擬混凝土的界面,采用納米壓痕技術(shù)測(cè)試了碳化前后界面過(guò)渡區(qū)的微結(jié)構(gòu)特征。實(shí)驗(yàn)結(jié)果表明：碳化后界面過(guò)渡區(qū)仍然存在,且其與基體的彈性模量和硬度值均有提高,界面過(guò)渡區(qū)尺寸由碳化前的約50-60μm降低到碳化后的約20～30μm。說(shuō)明碳化后界面過(guò)渡區(qū)仍然是CO2擴(kuò)散的快速通道。界面過(guò)渡區(qū)孔隙率等微結(jié)構(gòu)在碳化前后的演變能揭示其碳化過(guò)程的混凝土性能變化的原因。本文對(duì)不同水膠比的界面試樣進(jìn)行了BSE實(shí)驗(yàn),根據(jù)BSE圖像分析了界面過(guò)渡區(qū)的形貌并定量分析了界面過(guò)渡區(qū)碳化前后孔隙率和物相組成的變化。實(shí)驗(yàn)表明,界面過(guò)渡區(qū)的孔隙(在孔尺寸不小于200nm的范圍)率高于基體,且碳化后孔隙率均有所降低,未水化水泥含量均有不同程度的減少。碳化后界面過(guò)渡區(qū)的孔隙率仍然高于基體,而其未水化水泥的減少量較基體多。最后,為了探討界面微結(jié)構(gòu)的改變對(duì)混凝土整體抗碳化性能的影響,本文設(shè)計(jì)了改變界面條件的骨料裹漿混凝土試件的碳化實(shí)驗(yàn)。實(shí)驗(yàn)結(jié)果表明：高水膠比的襄漿骨料會(huì)提高混凝土的整體有效水膠比,增加碳化深度,降低了混凝土整體抗碳化性能。SEM圖像分析表明.相同混凝土水膠比下,裹漿骨料的界面較非裹漿的界面結(jié)構(gòu)疏松,孔隙率大。
[Abstract]:The carbonization reaction of cement concrete refers to the neutralization reaction between the carbon dioxide in the atmosphere and the calcium hydroxide, C-S-H gel, ettringite and the like dissolved in the pore solution through the pores or cracks of the concrete. The neutralization reaction of concrete results in shrinkage of cement stone and cracks. and the service life of the concrete is shortened. The carbonization reaction can cause the change of microstructure inside the concrete, and the various microstructure characteristics of the concrete can also have different influences on the carbonization process. The microstructure of concrete mainly consists of its phase composition, porosity, pore size distribution and so on. It can be divided into interface transition zone and matrix part. The interface transition zone is the weak link of concrete, and the interface transition zone and its microstructure have an important influence on its transmission performance and durability. The interface transition zone and its microstructure must also be an important aspect of the carbonization process of concrete, which can provide the basis for establishing concrete carbonation model considering interface effect. In this paper, the microstructure of interface transition zone before and after carbonization is characterized by interfacial carbonization depth test and nano mechanical properties, and the evolution law of interface transition zone microstructure before and after carbonization is studied by using back scattering (BSE) image analysis technique. The effect of aggregate-matrix interface on carbonization of cement concrete was studied in four aspects: the effect of the interface characteristics on the carbonization resistance of concrete. Due to the difference between the interface transition zone and the microstructure of the matrix, different carbonization phenomena must occur during the carbonization process. the interface transition zone has the characteristics of large porosity, loose structure, high calcium hydroxide content and directional distribution, low hydration cement content and the like, so that the carbonization rate of the interface is fast to the matrix. In this paper, a rule-shaped aggregate is designed. According to the carbonization test of matrix interface, a net slurry test piece with water-cement ratio of 0. 60, 0. 53 and 0. 35 was formed, and the two ends of the test piece were carbonized at the carbonization surface for 28d, and the carbonization depth of the interface and the substrate was measured by TUNEL method. The experimental results show that the carbonization depth of the interface is 2-3 times that of the matrix, and the carbonization curve is formed in the vicinity of the interface under the influence of the carbonization interface effect. Therefore, the transmission speed of CO2 is several times the transmission speed of the base material, and the interface transmission is one of the reasons for forming part of the carbonization zone. In this paper, the physical model of carbonization of cement-based material considering ITZ effect is presented. Nanoindentation technique can test the nano mechanical properties of interface transition zone and characterize the microstructure of interface transition zone, thus revealing the evolution law of microstructure of interface transition zone before and after carbonization. In this paper, the interface of the simulated concrete with different water-cement ratio is designed, and the microstructure characteristics of the interface transition zone before and after carbonization are tested by using nano-indentation technology. The results show that the transition area of the interface still exists after carbonization, and the elastic modulus and hardness value of the interface are improved. The size of the interface transition zone is reduced from about 50-60. m u.m before carbonization to about 20 ~ 30. m The evolution of the microstructure before and after carbonization can reveal the change of the concrete properties of the carbonization process. In this paper, BSE experiment was carried out on the interface sample with different water-cement ratio, the morphology of interface transition zone was analyzed according to BSE image, and the change of porosity and phase composition before and after carbonization of interface transition zone was quantitatively analyzed. The experimental results show that the porosity of the interface transition zone (in the range of not less than 200nm) is higher than that of the matrix, and the porosity after carbonization decreases and the content of unhydrated cement is decreased. The porosity of the transition zone of the post-carbonization interface is still higher than that of the matrix, and the amount of unhydrated cement is much lower than that of the matrix. Finally, in order to investigate the effect of the change of interface microstructure on the whole anti-carbonization performance of concrete, this paper designs the carbonization experiment of aggregate-wrapped concrete test piece which changes the interface condition. The experimental results show that the cement mortar aggregate with high water-cement ratio can improve the overall effective water-cement ratio of concrete, increase the carbonization depth, and reduce the overall anti-carbonization performance of concrete. SEM image analysis showed. Under the same concrete water-cement ratio, the interface between the interface of the slurry-wrapped aggregate and the non-wrapped slurry is loose and the porosity is large.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TU528

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