【摘要】：硫氧鎂水泥具有輕質(zhì)、堿度低、防火、裝飾效果好等優(yōu)點(diǎn),但其存在強(qiáng)度低、抗水性差的缺點(diǎn),限制了其大規(guī)模應(yīng)用。本文采用外加劑技術(shù)制備了一種高強(qiáng)、抗水、抗腐蝕、抗碳化及具有良好護(hù)筋性能的堿式硫酸鎂水泥,并系統(tǒng)研究了堿式硫酸鎂水泥的物相結(jié)構(gòu)、水化產(chǎn)物、力學(xué)性能、耐久性能及在土木工程中的應(yīng)用技術(shù),取得主要研究成果如下:1.合成了純的堿式硫酸鎂新相,結(jié)合初始原料配比、XRD分析、化學(xué)分析和熱分析結(jié)果,確定其組成為5Mg(OH)2·Mg SO4·7H2O,形貌為針桿狀晶體;在Topas 4.2軟件中采用模擬退火法解析出5Mg(OH)2·Mg SO4·7H2O為單斜晶體,所屬空間群為C121,晶胞參數(shù)為:a=15.14?、b=6.31?、c=10.26?、β=103.98o,晶體密度為1.87 g/cm3。該晶體是由Mg-O八面體為骨架,SO42-、H2O和OH-為填充離子(或分子)的層狀結(jié)構(gòu)。2.外加劑K2、K7、K8、K19、K21、K27、K30、K31、K32和K34均可明顯改善堿式硫酸鎂水泥的強(qiáng)度。硫酸鎂溶液濃度一定時,堿式硫酸鎂水泥的強(qiáng)度隨Mg O/Mg SO4摩爾比增加而提高。相同摩爾比時,堿式硫酸鎂水泥的強(qiáng)度高于氯氧鎂水泥,且堿式硫酸鎂水泥不易出現(xiàn)吸潮返鹵現(xiàn)象。與硅酸鹽水泥相比,堿式硫酸鎂水泥具有更低的孔隙率;與氯氧鎂水泥相比,堿式硫酸鎂水泥的孔隙溶液濃度更低,且電阻率遠(yuǎn)大于氯氧鎂水泥。堿式硫酸鎂水泥的強(qiáng)度高于硫氧鎂水泥的主要原因是其水化完全,且致密的微觀結(jié)構(gòu)中含有大量針狀5Mg(OH)2·Mg SO4·7H2O。3.傳統(tǒng)硫氧鎂水泥凈漿試件泡水28d后開裂、奔潰,原因是低活性Mg O水化產(chǎn)生結(jié)晶應(yīng)力,破壞水泥結(jié)構(gòu)。堿式硫酸鎂水泥具有更加優(yōu)異的抗水性能,無礦物摻合料時,堿式硫酸鎂水泥凈漿試件泡水180d的軟化系數(shù)可達(dá)0.85以上。摻加粉煤灰的堿式硫酸鎂水泥的抗水性能可進(jìn)一步提高,泡水180d軟化系數(shù)可達(dá)0.98。原因在于外加劑延緩了Mg O在水中水化的速度,削弱了Mg O水化產(chǎn)生的結(jié)晶應(yīng)力,且強(qiáng)度相5Mg(OH)2·Mg SO4·7H2O的溶解度較低(0.034 g/100 g)。4.堿式硫酸鎂水泥與傳統(tǒng)硫氧鎂水泥相比具有優(yōu)異的抗水熱、抗氯化鎂溶液腐蝕、抗碳化和護(hù)筋性能。摻加礦渣的堿式硫酸鎂水泥在80℃下水熱處理14d不出現(xiàn)開裂。浸泡鹵水8個月,堿式硫酸鎂水泥強(qiáng)度不降反升。堿式硫酸鎂水泥在加速碳化環(huán)境中,不出現(xiàn)碳化現(xiàn)象。堿式硫酸鎂水泥中鋼筋銹蝕程度遠(yuǎn)低于在氯氧鎂水泥中的情況。堿式硫酸鎂水泥中鋼筋的早期銹蝕速率高于硅酸鹽水泥,后期逐漸降低,甚至?xí)陀诠杷猁}水泥中的鋼筋銹蝕速率。摻加少量亞硝酸鹽阻銹劑時,堿式硫酸鎂水泥中鋼筋幾乎不銹蝕。5.堿式硫酸鎂水泥有望大規(guī)模應(yīng)用于土木工程。以堿式硫酸鎂水泥為主要膠凝材料制備的閉孔膨脹珍珠巖砂漿、化學(xué)發(fā)泡、物理發(fā)泡等保溫材料,具有強(qiáng)度高、密度低、保溫效果好、防火等性能。內(nèi)摻40%粉煤灰的堿式硫酸鎂水泥膠砂試件的28d抗壓強(qiáng)度達(dá)57.7MPa,達(dá)到52.5R硅酸鹽水泥的強(qiáng)度,抗折強(qiáng)度達(dá)16.2MPa,是62.5硅酸鹽水泥的2倍。以堿式硫酸鎂水泥為膠凝材料可制備出C20~C50等強(qiáng)度等級的砂石混凝土,且其抗凍性優(yōu)于普通硅酸鹽水泥混凝土。以堿式硫酸鎂水泥為可制備具有韌性好、承載力高的鋼筋混凝土構(gòu)件,其中鋼筋的銹蝕速率較低,四個月內(nèi)鋼筋的銹蝕率僅為2‰~3.5‰,平均銹蝕速率僅為氯氧鎂水泥混凝土中的2‰左右,是礦渣硅酸鹽水泥混凝土中的6‰左右。
[Abstract]:Magnesium oxysulfate cement has the advantages of light weight, low alkalinity, fire protection and good decorative effect, but its disadvantages of low strength and poor water resistance limit its large-scale application.In this paper, a kind of high strength, water resistance, corrosion resistance, carbonization resistance and good reinforcement protection performance of magnesium oxysulfate cement was prepared by using additive technology. The main research results are as follows: 1. Pure basic magnesium sulfate new phase was synthesized and its composition was determined to be 5Mg(OH)2.Mg SO4.7H2O by XRD analysis, chemical analysis and thermal analysis. In Topas 4.2 software, 5Mg(OH)2.Mg SO4.7H2O was determined as monoclinic crystal by simulated annealing. The space group belongs to C121. The cell parameters are: a = 15.14?, B = 6.31?, C = 10.26?, beta = 103.98o, and the crystal density is 1.87 g/cm 3. The crystal is a layered structure with Mg-O octahedron as skeleton, SO42-, H2O and OH - as filling ions (or molecules). K2, K7, K8, K19, K21, K27, K30, K31, K32 and K34 can obviously improve the strength of basic magnesium sulfate cement. When the concentration of magnesium sulfate solution is constant, the strength of basic magnesium sulfate cement increases with the increase of molar ratio of Mg O/Mg SO4. At the same molar ratio, the strength of basic magnesium sulfate cement is higher than that of magnesium oxychloride cement, and basic magnesium sulfate cement is not easy to appear. Compared with Portland cement, basic magnesium sulfate cement has lower porosity; compared with magnesium oxychloride cement, basic magnesium sulfate cement has lower concentration of pore solution, and its resistivity is much higher than that of magnesium oxychloride cement. There are a lot of acicular 5Mg(OH)2.Mg SO4.7H2O.3 in the microstructure. The traditional magnesium sulfate cement paste cracks after soaking for 28 days, which is due to the crystallization stress produced by the hydration of low active Mg O and the destruction of cement structure. The softening coefficient of alkaline magnesium sulfate cement mixed with fly ash can be further improved, and the softening coefficient can reach 0.98 after soaking for 180 days. The reason is that the admixture retards the hydration rate of Mg O in water, weakens the crystallization stress produced by hydration of Mg O, and the solubility of the strength phase 5Mg(OH)2.Mg SO4.7H2O is lower (0.03). 4 g/100 g). 4. Compared with the traditional magnesium sulfate cement, the basic magnesium sulfate cement has excellent hydrothermal resistance, resistance to magnesium chloride solution corrosion, resistance to carbonization and reinforcement protection properties. The basic magnesium sulfate cement with slag does not crack after hydrothermal treatment at 80 C for 14 days. After soaking in brine for 8 months, the strength of the basic magnesium sulfate cement does not decrease but rises. In the accelerated carbonation environment, there is no carbonation. The corrosion degree of steel bars in the basic magnesium sulfate cement is much lower than that in the magnesium oxychloride cement. Basic magnesium sulfate cement is expected to be widely used in civil engineering. Closed-cell expanded perlite mortar, chemical foaming, physical foaming and other insulation materials made of basic magnesium sulfate cement as the main cementing material, have high strength, low density, good insulation effect, fire protection and other properties. The 28-day compressive strength of the basic magnesium sulfate cement mortar with 40% fly ash is 57.7 MPa and 52.5 R Portland cement. The flexural strength is 16.2 MPa, twice that of 62.5 Portland cement. The sand-stone concrete with strength grades of C20~C50 can be prepared by using basic magnesium sulfate cement as cementing material, and its frost resistance is better than that of ordinary silicon cement. Portland cement concrete. Making use of basic magnesium sulfate cement as a kind of reinforced concrete component with good toughness and high bearing capacity, the corrosion rate of steel bars is low, the corrosion rate of steel bars is only 2~3.5, the average corrosion rate is only about 2 in magnesium oxychloride cement concrete, which is 6 in slag Portland cement concrete. About a thousand per thousand.
【學(xué)位授予單位】：中國科學(xué)院研究生院(青海鹽湖研究所)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TQ172.1

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