磷酸镁水泥的耐高温改性及粘贴碳纤维布面内剪切性能研究

发布时间：2018-05-10 23:39

本文选题：磷酸镁水泥 + 硅灰石粉　；参考：《哈尔滨工业大学》2017年博士论文

【摘要】：磷酸镁水泥和普通水泥相比具有很多优点,例如:凝结速度快、早期强度高、与不同材料之间的粘结力强、干缩小、耐磨性好等。这些优点使得磷酸镁水泥可以广泛地应用于建筑物修补与加固工程中。国内外对于磷酸镁水泥的耐高温性能研究较少,特别是关于耐高温性能改善方法与相关机理还不清楚。同时,有机胶外贴碳纤维布加固混凝土结构已经在全世界范围内得到系统研究与广泛应用;尽管碳纤维丝在绝氧条件下具有良好的耐高温性能,但是普遍采用的环氧类胶粘剂的性能在高温下会迅速劣化。为了提高外贴碳纤维布加固混凝土结构的适用范围与耐高温性能,采用耐高温优良的无机胶代替有机环氧类胶粘剂是一个重要发展方向。本文的一个研究重点是硅灰石对磷酸镁水泥耐高温性的改性效果与作用机理。研究结果发现:随着硅灰石掺量的增加,硅灰石改性磷酸镁水泥的抗折强度和抗压强度不断增加。磷酸镁水泥具有优良的抗冻融能力、抗干湿循环的性能以及耐水和耐硫酸盐侵蚀性能,但是磷酸镁水泥试件在强碱及强酸中的力学性能却会大幅下降。利用SEM-EDS发现硅灰石没有参与化学反应,没有影响磷酸镁水泥原有水化产物的生成。但是纤维状的硅灰石填补在磷酸镁水泥中的缝隙中,使得磷酸镁水泥的结构更加密实,从而提高了磷酸镁水泥的抗压强度。通过研究磷酸镁水泥高温后基本力学性能试验得知:硅灰石的掺加对试件高温后的质量损失影响不大,掺加了硅灰石的磷酸镁水泥在温度高达600℃时抗压强度没有降低。虽然硅灰石加入磷酸镁水泥之后没有直接参与化学反应,经过高温处理后也没有改变磷酸镁水泥的化学产物和物相变化。但是硅灰石本身在经历1000℃高温后的化学稳定性良好,正是这种具有高温稳定的微米级纤维状硅灰石限制了磷酸镁水泥水化产物的脱水收缩而减轻了其力学强度衰减。本文的另一个研究重点是改性磷酸镁水泥作为胶粘剂的混凝土外贴碳纤维布的剪切强度及其随不同温度与环境条件作用后的演变规律,为磷酸镁水泥代替环氧树脂胶应用于碳纤维布加固混凝土结构奠定基础。结果发现:改性磷酸镁水泥代替环氧树脂胶可使碳纤维布粘贴混凝土试件的剪切强度提高40%以上,同时使经历105~500℃高温后的剪切强度损失率显著降低。经过不同高温处理后的改性磷酸镁水泥加固试件都没有发生最理想的破坏形式:即胶层下混凝土被撕下一层。这最主要应该是高温下改性磷酸镁水泥抗剪强度逐渐降低引起的。用改性磷酸镁水泥粘贴碳纤维布的混凝土双剪试件经历干湿循环、自来水浸泡、MgSO_4溶液侵蚀后的粘结性能均优于用环氧树脂粘贴碳纤维布的混凝土双剪试件的粘结性能,但是其抗硫酸侵蚀能力、抗Na OH溶液侵蚀能力、抗Na2SO_4溶液侵蚀能力却比用环氧树脂粘贴碳纤维布的混凝土双剪试件略差。总之,硅灰石的加入有效提高了磷酸镁水泥的耐高温性能。改性磷酸镁水泥的粘结性能比环氧树脂更优良,其可以作为一种新型无机胶体来粘贴碳纤维布加固钢筋混凝土结构。虽然在高温后磷酸镁水泥双剪试件的破坏形式都没有发生与胶层毗邻的混凝土完全剥离的破坏形式,而发生的是纤维布的剥离破坏,但是其常温下和高温后良好的粘结性能证明用磷酸镁水泥代替环氧树脂作胶粘剂粘贴碳纤维布用于实际工程加固是可行的。同时,磷酸镁水泥作为胶粘剂粘贴碳纤维布加固混凝土结构还具有良好的经济性和环保性效益。
[Abstract]:Magnesium phosphate cement has many advantages compared with ordinary cement, such as quick setting speed, high early strength, strong adhesive force with different materials, dry shrinkage and good wear resistance. These advantages make magnesium phosphate cement can be widely used in building repair and strengthening process. In addition, it is not clear that the methods for improving the performance of high temperature resistance and the related mechanism are not clear. At the same time, the concrete structure strengthened with carbon fiber cloth outside the organic glue has been systematically studied and widely used worldwide. Although the carbon fiber wire has good high temperature resistance under the anaerobic condition, the epoxy adhesive is commonly used. The performance of the agent will deteriorate rapidly at high temperature. In order to improve the application range and high temperature resistance of the reinforced concrete structure reinforced with the external carbon fiber cloth, it is an important development direction to replace the organic epoxy adhesive with high temperature resistant inorganic glue. The results show that with the increase of the amount of wollastonite, the flexural strength and compressive strength of the cement modified by Wollastonite are increasing. The magnesium phosphate cement has excellent resistance to freezing and thawing, the performance of anti dry and wet cycle and the resistance to water and sulphate resistance, but the magnesium phosphate cement test is in strong alkali and strong acid. The mechanical properties of the MFP are not involved in the chemical reaction, which does not affect the formation of the original hydration products of the magnesium phosphate cement. But the fibrous wollastonite fills in the gap in the magnesium phosphate cement, making the structure of the magnesium phosphate cement more compacting, thus improving the compressive strength of the magnesium phosphate cement. Through the study of the basic mechanical properties of magnesium phosphate cement after high temperature, it is found that the addition of wollastonite has little effect on the mass loss after high temperature. The compressive strength of magnesium phosphate cement mixed with wollastonite does not decrease when the temperature is up to 600 C. Although the silica fume stone has not been directly involved in chemical reaction after adding magnesium phosphate cement, it has not been directly involved. The chemical products and phase changes of magnesium phosphate cement are not changed after high temperature treatment. But the chemical stability of wollastonite itself after the high temperature of 1000 degrees C is good. It is this kind of high temperature stable micron grade fibrous wollastonite that restricts the dehydration shrinkage of the hydrated magnesium phosphate and reduces the attenuation of its mechanical strength. Another research focus is on the shear strength of modified magnesium phosphate cement as the adhesive and its shear strength with different temperature and environmental conditions. It lays a foundation for the construction of CFRP reinforced concrete structure for the replacement of epoxy resin by magnesium phosphate cement. The result is that modified magnesium phosphate cement is found. The shear strength of the CFRP bonded concrete specimen can be increased by more than 40%, and the shear strength loss rate after high temperature 105~500 C is significantly reduced. The most ideal failure form of the modified magnesium phosphate cement after different high temperature treatment has not occurred: the concrete under the rubber layer is torn down. The main reason is that the shear strength of modified magnesium phosphate cement is gradually reduced at high temperature. The concrete double shear specimens with modified magnesium phosphate cement paste carbon fiber cloth experience dry and wet cycle and tap water immersion. The bonding properties of MgSO_4 solution are better than that of concrete double shear specimens with epoxy resin bonded CFRP. Performance, but its resistance to sulphuric acid corrosion, anti Na OH solution erosion ability, anti Na2SO_4 solution erosion ability is slightly worse than that of concrete double shear with epoxy resin bonded carbon fiber cloth. In conclusion, the addition of wollastonite effectively improves the high temperature resistance of magnesium phosphate cement. The adhesive properties of modified magnesium phosphate cement are better than that of epoxy resin. Well, it can be used as a new type of inorganic colloid to paste the reinforced concrete structure with carbon fiber cloth. Although after high temperature, the destruction form of the double shear specimens of the magnesium phosphate cement has not occurred in the form of the complete dissection of the concrete adjacent to the cement, but it is dispeeled and destroyed by the fiber cloth, but it is good at normal temperature and after high temperature. It is proved that it is feasible to use magnesium phosphate cement instead of epoxy as adhesive to paste carbon fiber cloth for practical engineering reinforcement. At the same time, magnesium phosphate cement as adhesive bonded CFRP reinforced concrete structure has good economic and environmental benefits.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TU528

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