本文關(guān)鍵詞： 活性粉末混凝土 海洋環(huán)境 凍融循環(huán) 耐久性 微觀分析 壽命預(yù)測　出處：《北京交通大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：摘要：在長期海水侵蝕和凍融循環(huán)的耦合作用下,沿海寒冷地區(qū)的海工混凝土結(jié)構(gòu)會出現(xiàn)內(nèi)部損傷、承載力下降以及使用功能退化等耐久性問題。為了延長這種惡劣環(huán)境下結(jié)構(gòu)的使用壽命,將具有良好力學(xué)性能和優(yōu)異耐久性的活性粉末混凝土用于海洋建筑結(jié)構(gòu)中的現(xiàn)實意義巨大。本文通過試驗研究和理論分析,在確定活性粉末混凝土中鋼纖維最優(yōu)體積摻量2%的基礎(chǔ)上,以粉煤灰、礦粉替代硅粉摻量為主要變化參數(shù),以C50高性能混凝土為對比試件,測定了各組試件的質(zhì)量損失率、抗壓強度損失率和不同深度處氯離子含量,并利用SEM研究了海水凍融循環(huán)前后試件內(nèi)部的微觀形貌變化,初步探索了海水凍融循環(huán)作用下活性粉末混凝土的耐久性,主要工作及結(jié)論如下： 海水凍融循環(huán)作用下,活性粉末混凝土的耐久性遠優(yōu)于C50高性能混凝土。由于活性粉末混凝土質(zhì)量隨著海水凍融循環(huán)作用的增加有所提高,不建議使用質(zhì)量損失率作為其抗海水凍融循環(huán)作用的評價指標(biāo),建議選用抗壓強度作為其抗海水凍融循環(huán)作用的評價指標(biāo)。粉煤灰或礦粉的摻入使活性粉末混凝土初始強度降低,同時,這兩種礦物摻合料都能夠顯著提高活性粉末混凝土在海水凍融循環(huán)作用下的耐久性。 海水凍融循環(huán)作用對混凝土微觀形貌產(chǎn)生的影響很大。SEM實驗結(jié)果表明：海水凍融循環(huán)作用后,C50高性能混凝土內(nèi)CH減少,AFt增多,還有黏聚性較低的鎂鹽類腐蝕產(chǎn)物生成；活性粉末混凝土有AFt晶體以及F鹽生成,未觀察到明顯的鎂鹽類物質(zhì)。 粉煤灰和礦粉對活性粉末混凝土中自由氯離子滲透性能的影響較大。結(jié)合Fick第二定律擬合出活性粉末混凝土的氯離子擴散系數(shù)D,最后再考慮擴散系數(shù)D的時間依賴性對其進行修正,結(jié)果表明活性粉末混凝土氯離子擴散系數(shù)隨時間變化呈指數(shù)關(guān)系。 建立凍融和氯離子侵蝕耦合作用下的結(jié)構(gòu)壽命預(yù)測模型。當(dāng)凍融破壞為主要影響因素時,C50高性能混凝土使用壽命小于30年,活性粉末混凝土使用壽命均大于80年；當(dāng)氯離子侵蝕破壞為主要影響因素時,對使用壽命進行了Monte Carlo數(shù)值模擬,發(fā)現(xiàn)隨機模擬得到的使用壽命較好的服從兩參數(shù)的Weibull分布,結(jié)果表明粉煤灰和礦粉均能夠提高使用壽命,但二者摻量變化使用壽命提高的規(guī)律不同,同時,增加保護層厚度是提高使用壽命的重要措施。
[Abstract]:Absrtact: under the coupling of seawater erosion and freeze-thaw cycle for a long time, the marine concrete structure in the cold coastal area will appear internal damage. Durability problems such as reduced bearing capacity and degradation of service functions. In order to prolong the service life of structures in this harsh environment. It is of great practical significance to use the reactive powder concrete with good mechanical properties and excellent durability in marine building structures. This paper is based on experimental research and theoretical analysis. On the basis of determining the optimal volume content of steel fiber in reactive powder concrete (RPC) 2%, the main variable parameters are fly ash and mineral powder instead of silica fume, and C50 high performance concrete as contrast specimen. The mass loss rate, compressive strength loss rate and chloride content at different depths were measured, and the microstructure of the specimens before and after seawater freeze-thaw cycle was studied by SEM. The durability of reactive powder concrete under seawater freeze-thaw cycle is preliminarily explored. The main work and conclusions are as follows: The durability of reactive powder concrete is much better than that of C50 high performance concrete under the action of seawater freeze-thaw cycle, because the quality of reactive powder concrete increases with the increase of seawater freezing and thawing cycle. It is not recommended to use the mass loss rate as the evaluation index of its anti-seawater freeze-thaw cycle. It is suggested that the compressive strength should be selected as the evaluation index of the anti-freezing and thawing effect of seawater. The initial strength of reactive powder concrete is reduced by the addition of fly ash or mineral powder, and at the same time. Both of these mineral admixtures can significantly improve the durability of reactive powder concrete under seawater freeze-thaw cycle. The effect of seawater freeze-thaw cycle on the microstructure of concrete is very great. SEM results show that the Ch in C _ (50) high performance concrete increases after seawater freeze-thaw cycle. There is also the formation of magnesium salt corrosion products with low agglomeration. AFt crystals and F salts were formed in the reactive powder concrete, and no obvious magnesium salts were observed. Fly ash and mineral powder have great influence on the free chloride ion permeability in reactive powder concrete. The chloride diffusion coefficient D of reactive powder concrete is fitted with Fick's second law. Finally, considering the time dependence of diffusion coefficient D, the results show that the chloride ion diffusion coefficient of reactive powder concrete varies exponentially with time. The structure life prediction model under the coupling of freezing and thawing and chloride ion erosion is established. When freeze-thaw failure is the main influencing factor, the service life of C50 high performance concrete is less than 30 years. The service life of reactive powder concrete is more than 80 years. When chloride erosion is the main factor, the Monte Carlo numerical simulation is carried out for the service life. It is found that the better service life obtained by random simulation is from the Weibull distribution of two parameters. The results show that both fly ash and mineral powder can improve the service life. However, the law of increasing service life is different between them. At the same time, increasing the thickness of protective layer is an important measure to improve the service life.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TV431

【參考文獻】

相關(guān)期刊論文 前10條

1 譚可可;葛濤;陳偉;王明洋;;RPC力學(xué)參數(shù)及抗接觸爆炸性能試驗[J];爆破;2007年01期

2 陳寶春;李生勇;余健;林上順;季韜;;大跨度活性粉末混凝土拱橋試設(shè)計[J];交通科學(xué)與工程;2009年01期

3 姜文輝,薛景,王世國;對嚴寒地區(qū)混凝土鹽凍破壞的認識[J];低溫建筑技術(shù);2003年03期

4 梁萌;李俊毅;盧秀敏;李曉明;;混凝土保護層厚度施工允許偏差[J];中國港灣建設(shè);2006年03期

5 安蕊梅;段樹金;;韓國首爾仙游人行拱橋[J];世界橋梁;2006年03期

6 劉斯鳳,孫偉,林瑋,賴建中;摻天然超細混合材高性能混凝土的制備及其耐久性研究[J];硅酸鹽學(xué)報;2003年11期

7 李莉;王英;鄭文忠;;活性粉末混凝土耐久性綜述[J];工業(yè)建筑;2008年S1期

8 孫叢濤;牛荻濤;;混凝土中氯離子擴散性能的深入探討[J];工業(yè)建筑;2010年09期

9 覃維祖,曹峰;一種超高性能混凝土——活性粉末混凝土[J];工業(yè)建筑;1999年04期

10 曹峰,覃維祖;超高性能纖維增強混凝土初步研究[J];工業(yè)建筑;1999年06期

，

本文編號：1468960