本文選題：活性粉末混凝土　切入點(diǎn)：模擬海水　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】：我國(guó)沿海地區(qū)混凝土結(jié)構(gòu)長(zhǎng)期處于海洋環(huán)境下,耐久性不足問(wèn)題普遍存在�；钚苑勰┗炷磷鳛橐环N具備超高強(qiáng)度、高韌性以及優(yōu)異耐久性的新型水泥基復(fù)合材料,十分適用于惡劣海洋服役環(huán)境下的海工結(jié)構(gòu)及混凝土結(jié)構(gòu)的防護(hù)。本文針對(duì)結(jié)構(gòu)物在海洋環(huán)境下遭受的海水侵蝕、干濕循環(huán)和凍融循環(huán)等作用,通過(guò)模擬海水的于濕循環(huán)、模擬海水的凍融循環(huán)、去硫酸根模擬海水的凍融循環(huán)作用試驗(yàn),研究了活性粉末混凝土在上述作用下力學(xué)性能的變化規(guī)律,并結(jié)合SEM、XRD等微觀方法分析了作用前后試件內(nèi)部的微觀形貌及侵蝕產(chǎn)物。主要工作及結(jié)論如下： (1)活性粉末混凝土在模擬海水的干濕循環(huán)作用下,隨著干濕循環(huán)次數(shù)的增加,抗壓強(qiáng)度呈先上升后下降趨勢(shì),劈裂抗拉強(qiáng)度呈現(xiàn)先下降后上升再下降趨勢(shì)。微觀試驗(yàn)表明：海水侵入活性粉末混凝土內(nèi)部后,發(fā)生了鎂鹽和硫酸鹽侵蝕,海水中的氯離子也導(dǎo)致了鋼纖維的銹蝕。 (2)活性粉末混凝土材料在模擬海水的凍融循環(huán)作用下,材料抗壓強(qiáng)度和劈裂抗拉強(qiáng)度總體上都隨凍融循環(huán)次數(shù)的增加而下降；SEM與XRD結(jié)果表明：在海水凍融循環(huán)作用下,活性粉末混凝土材料內(nèi)部的孔隙內(nèi)及缺陷處易發(fā)生侵蝕,可觀察到明顯的鈣礬石和石膏,以及少量鎂鹽和硫酸鹽類侵蝕產(chǎn)物。 (3)活性粉末混凝土材料在去硫酸根模擬海水的凍融循環(huán)作用下,隨凍融循環(huán)次數(shù)的增加,抗壓強(qiáng)度和劈裂抗拉強(qiáng)度總體依然呈下降趨勢(shì),但與未去除硫酸根的海水凍融循環(huán)作用相比,材料抗壓強(qiáng)度下降幅度減小。SEM與XRD試驗(yàn)中沒(méi)有發(fā)現(xiàn)大量的侵蝕產(chǎn)物,僅在試驗(yàn)后期觀察到由于材料再水化生成的少量鈣礬石,由此可推斷在海水凍融循環(huán)作用過(guò)程中硫酸根離子是引起活性粉末混凝土抗壓強(qiáng)度劣化的重要因素之一。
[Abstract]:The concrete structure in coastal areas of China has been in marine environment for a long time, and the problem of insufficient durability is widespread. Reactive powder concrete is a new type of cement matrix composite with ultra-high strength, high toughness and excellent durability. It is very suitable for the protection of marine structures and concrete structures in the severe marine service environment. In this paper, in view of the effects of seawater erosion, dry and wet circulation and freezing and thawing cycle on structures in the marine environment, we simulate the wet circulation of sea water. The mechanical properties of reactive powder concrete (RPC) under the above action were studied by simulating the freezing and thawing cycle of seawater and desulphuric acid radical under the experiment of freezing and thawing cycle of seawater. The microstructure and erosion products of the specimens before and after the action were analyzed by means of SEM XRD and other microcosmic methods. The main work and conclusions are as follows:. 1) under the dry and wet cycle of simulated seawater, the compressive strength of the reactive powder concrete increases first and then decreases with the increase of the times of dry and wet cycles. The splitting tensile strength decreased first and then increased and then decreased. The microscopic test showed that magnesium salt and sulfate erosion occurred after seawater invaded into the reactive powder concrete and the chloride ions in seawater also led to the corrosion of steel fiber. (2) the compressive strength and splitting tensile strength of reactive powder concrete materials decreased with the increase of the number of freeze-thaw cycles under the simulated freeze-thaw cycles of seawater. The results of SEM and XRD showed that: under the action of freeze-thaw cycles in seawater, the compressive strength and splitting tensile strength of the materials decreased with the increase of freeze-thaw cycles. In the interior of reactive powder concrete, ettringite and gypsum, as well as a small amount of magnesium salt and sulphate, are easily eroded in the pores and defects. (3) the compressive strength and splitting tensile strength of reactive powder concrete materials under the action of desulphate simulated seawater freeze-thaw cycle increase with the increase of freeze-thaw cycle times, and the compressive strength and splitting tensile strength still show a downward trend. However, compared with the freeze-thaw cycle without sulfate removal, the decrease in compressive strength of the material was reduced. There was no large amount of erosion products found in the XRD and XRD tests. Only a small amount of ettringite was observed in the later stage of the test because of the rehydration of the material. It can be concluded that sulfate ion is one of the important factors that cause the compressive strength deterioration of reactive powder concrete during the freeze-thaw cycle of seawater.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU528

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本文編號(hào)：1630056