本文選題：粉煤灰　切入點：礦渣　出處：《東北電力大學(xué)》2017年碩士論文

【摘要】：高強混凝土因具有強度高,耐久性好,變形小等優(yōu)點,能適應(yīng)現(xiàn)代工程結(jié)構(gòu)向著高層、大跨、重載發(fā)展,已經(jīng)也必將得到更廣泛的應(yīng)用。與此同時,混凝土的耐久性危機也日益顯現(xiàn)。寒冷地區(qū)的海港及海邊建筑物,同時經(jīng)受著凍融和氯鹽侵蝕的雙重作用,結(jié)構(gòu)表面出現(xiàn)剝落,鋼筋銹蝕等情況,嚴(yán)重影響了建筑物的長期使用和安全運行。因此本文從外加摻合料入手,研究摻量對高強混凝土性能的影響以及氯鹽環(huán)境下高強混凝土受彎梁的凍融損傷情況,為工程應(yīng)用提供依據(jù)。主要研究內(nèi)容及結(jié)論如下:(1)采用粉煤灰和礦渣作為摻合料,以膠凝材料總量的40%和50%取代水泥配制高強混凝土,通過掃描電鏡和X射線衍射技術(shù)研究了不同齡期時混凝土的水化產(chǎn)物和水化程度,分析了微觀結(jié)構(gòu)變化對宏觀強度的影響。結(jié)果表明,摻加礦物摻合料的混凝土早期強度較低,7d時礦渣已經(jīng)開始水化,粉煤灰在早期只起到填充作用,但摻合料混凝土后期強度增長迅速,可以達(dá)到基準(zhǔn)混凝土的2-5倍。復(fù)摻粉煤灰和礦渣的混凝土強度高于單摻礦物摻合料的混凝土,微觀試驗可以看出二者復(fù)摻產(chǎn)生的疊加效應(yīng)能夠促進(jìn)混凝土的二次水化,產(chǎn)生較多水化產(chǎn)物使結(jié)構(gòu)致密。(2)通過快速凍融試驗和電通量試驗對不同摻量和復(fù)摻比下高強混凝土的抗凍性和抗氯離子滲透性能進(jìn)行研究,并提出運用抗凍耐久性系數(shù)與電通量的比值綜合評價高強混凝土的耐久性能。結(jié)果表明:在摻合料總量不變的情況下,混凝土的抗凍性和抗氯離子滲透性能均隨著粉煤灰摻入量的增加和礦渣摻入量的減小而逐漸提升,但摻合料總質(zhì)量的增加會降低抗氯離子滲透性能;采用抗凍耐久性指數(shù)與電通量之比可較好的綜合評價高摻合料高強混凝土的耐久性,耐久性較好的適宜配合比為摻合料總量50%,粉煤灰與礦渣摻量比為4:1。(3)對已有的氯離子侵蝕過程仿真的細(xì)胞自動機模型進(jìn)行改進(jìn),引入摻合料的影響因素,建立了摻合料混凝土氯離子侵蝕過程模擬的細(xì)胞自動機模型,運用Matlab編制的程序?qū)胶狭匣炷恋穆入x子侵蝕過程進(jìn)行數(shù)值模擬。結(jié)果表明:現(xiàn)場暴露實驗結(jié)果與模擬結(jié)果基本一致,運用細(xì)胞自動機原理模擬摻合料混凝土中氯離子的擴散是合理且可行的,且模型更適合模擬混凝土在長期齡期作用下氯離子的侵蝕過程。(4)制作高強混凝土受彎梁(120mm×200mm×1200mm)進(jìn)行氯鹽環(huán)境下的氣凍氣融試驗,采用無損檢測的方法對凍融后受彎梁的損傷層厚度和混凝土的強度進(jìn)行檢測,并測定凍融循環(huán)300次后受彎梁的極限承載力。結(jié)果表明:受彎梁的凍融破壞主要表現(xiàn)為細(xì)小裂紋的出現(xiàn)及發(fā)展,凍融循環(huán)300次,受彎梁的極限承載力降低,損傷層厚度不斷加深,混凝土強度不斷降低,并建立了凍融循環(huán)次數(shù)與受彎梁損傷層厚度和混凝土強度變化間的關(guān)系。
[Abstract]:Because of its advantages of high strength, good durability and low deformation, high strength concrete can adapt to the development of modern engineering structures towards tall buildings, long spans and heavy loads, so it will be used more widely.At the same time, the durability crisis of concrete also appears day by day.The seaports and seaside buildings in cold areas are subjected to the double effects of freezing and thawing and chlorine salt erosion, the spalling of the structure surface and the corrosion of steel bars have seriously affected the long-term use and safe operation of the buildings.In this paper, the influence of admixture on the performance of high strength concrete and the freeze-thaw damage of high strength concrete flexural beam under chloride environment are studied in this paper, which provides the basis for engineering application.The main research contents and conclusions are as follows: (1) fly ash and slag are used as admixtures to prepare high strength concrete with 40% and 50% of total cementing material instead of cement.The hydration products and hydration degree of concrete at different ages were studied by means of scanning electron microscope and X-ray diffraction technique. The influence of microstructure change on macroscopic strength was analyzed.The results show that when the early strength of concrete mixed with mineral admixture is lower than 7 days, slag hydration has begun, and fly ash only plays a filling role in the early stage, but the later strength of concrete with mineral admixture increases rapidly, which can be 2-5 times of that of standard concrete.The strength of concrete mixed with fly ash and slag is higher than that of concrete with single mineral admixture. The microcosmic test shows that the superposition effect can promote the secondary hydration of concrete.Through rapid freeze-thaw test and electric flux test, the frost resistance and chloride ion permeation resistance of high strength concrete with different admixture and compound ratio were studied.The ratio of frost durability coefficient and electric flux is used to evaluate the durability of high strength concrete.The results show that the frost resistance and chloride ion permeability of concrete are improved with the increase of fly ash and the decrease of slag content.However, the increase of the total mass of admixtures will reduce the permeability of chloride ions, and the ratio of freezing durability index to electric flux can be used to evaluate the durability of high strength concrete with high admixture.The suitable mix ratio for durability is the total amount of admixture 50 and the ratio of fly ash to slag is 4: 1. 3) the existing cellular automata model of chloride ion erosion simulation is improved, and the influence factors of the admixture are introduced.The cellular automata model of chloride ion erosion process simulation of admixture concrete was established. The process of chloride ion erosion was simulated by Matlab program.The results show that the results of field exposure experiments are in good agreement with the simulation results. It is reasonable and feasible to simulate the chloride ion diffusion in admixture concrete by using the cellular automata principle.The model is more suitable for simulating the chloride erosion process of concrete under long-term age. (4) making high-strength concrete flexural beam (120mm 脳 200mm 脳 1200mm) to conduct air-freeze-gas melting test in chloride environment.The damage layer thickness and concrete strength of freeze-thaw flexural beams were measured by nondestructive testing method, and the ultimate bearing capacity of the beams after 300 freeze-thaw cycles was measured.The results show that the freeze-thaw failure of bending beams is mainly manifested by the appearance and development of small cracks, 300 cycles of freeze-thaw cycles, the reduction of ultimate bearing capacity, the deepening of damage layer thickness, and the decreasing of concrete strength.The relationship between the number of freeze-thaw cycles and the thickness of damaged layer and the strength of concrete is established.
【學(xué)位授予單位】：東北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU528

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