碱激发矿渣粉煤灰水泥早期水化及收缩特性研究
发布时间：2018-08-14 11:57
【摘要】：碱-激发胶凝材料具有早强高强、低水化热、耐酸碱腐蚀性好、抗氯离子腐蚀性强和抗渗抗冻性良好等特性，但也存在着诸如快凝、收缩大、易产生裂缝和可能潜在碱骨料反应危害等问题。其中由于收缩导致的混凝土开裂会影响耐久性，这也成为制约其应用和发展最主要的原因。碱-激发胶凝材料的水化和收缩性能受到胶凝组分的特性和激发剂的种类与掺量等多种因素的共同影响。而粉煤灰的加入对其水化发展历程和收缩变形特性都有很大影响。配比设计良好的碱-激发矿渣/粉煤灰水泥能在保证强度的同时降低费用并提高成型质量，但是目前对其水化和收缩特性的研究还不够系统。 本文旨在针对Me2O MeO Me2O3 SiO2 H2O和Me2O Me2O3 SiO2 H2O两个体系研究水玻璃模数、矿渣掺量和温度对碱-激发矿渣/粉煤灰水泥水化放热特性的影响，并对其进行动力学分析和表征；同时研究自收缩和干燥收缩的影响因素及其影响规律，探究最佳的减缩方式。 研究结果表明：碱-激发矿渣/粉煤灰水泥在不同水化阶段的水化放热速率不同。水化初期矿渣和粉煤灰中的钙硅离子逐渐溶出，水玻璃则水解生成NaOH和Si(OH)4。当反应进行到0.5~6h时，第一个水化放热峰出现，温度越高，水化初期和第一个峰的出峰时间跨度越短。继续水化到1~12h，可能出现第二个水化放热峰。在相同的水化温度下，碱-激发矿渣/粉煤灰水泥的水化放热速率随着矿渣掺量的增多和水玻璃模数的增加而逐渐加快。水化动力学计算得出其表观活化能也随着配比的不同而呈现一定的变化规律。 NaOH激发的矿渣/粉煤灰水泥自收缩相对较小，水玻璃激发的则较大，且在水玻璃模数为0.5~1.5范围内，随着水玻璃模数的增加，自收缩随之减小，变化速率也逐渐减慢。而在相同的水玻璃模数下，，自收缩随着矿渣掺量的减少而减小。 碱-激发矿渣/粉煤灰水泥的干燥收缩率随着矿渣掺量的增加而减小，随着水玻璃模数的增大而增大。指数函数式的回归方程对干缩随龄期变化的曲线的拟合较好，能有效预测不同龄期的干燥收缩率。随着矿渣掺量的减少，碱-激发矿渣/粉煤灰水泥56天内的质量损失不断增大。NaOH激发的矿渣/粉煤灰水泥的干缩值和质量损失呈线性关系，且矿渣掺量越大，直线的斜率越大。掺氧化烯醇类的减缩剂对减少碱-激发矿渣/粉煤灰水泥砂浆干燥收缩的效果明显，而氧化镁膨胀剂的减缩效果稍差。
[Abstract]:Alkali-activated cementing materials have the characteristics of early strength and high strength, low heat of hydration, good corrosion resistance to acid and alkali, strong corrosion resistance to chloride ions and good resistance to seepage and freezing, but they also have such characteristics as fast solidification and large shrinkage. It is easy to produce cracks and potential alkali-aggregate reaction hazards and so on. The cracking of concrete caused by shrinkage will affect the durability, which is the main reason that restricts its application and development. The hydration and shrinkage properties of alkali-activated cementitious materials are influenced by many factors, such as the properties of the gelling components and the types and contents of the activators. The addition of fly ash has great influence on hydration development and shrinkage deformation. The alkali-activated slag / fly ash cement with good proportioning design can reduce the cost and improve the molding quality while ensuring the strength, but the research on its hydration and shrinkage characteristics is not systematic. The purpose of this paper is to study the effects of water glass modulus, slag content and temperature on the hydration heat release characteristics of alkali-activated slag / fly ash cement in Me2O / MeO / Me2O3 / SiO2 and Me2O Me2O3 / SiO2 / H _ 2O systems, and to analyze and characterize their kinetics. At the same time, the influencing factors and the law of autogenous shrinkage and drying shrinkage were studied, and the best way of reducing shrinkage was explored. The results show that the hydration heat release rate of alkali-activated slag / fly ash cement is different in different hydration stages. In the early stage of hydration, calcium and silicon ions in slag and fly ash were gradually dissolved, while water glass was hydrolyzed to form NaOH and Si (OH) _ 4. The first hydration exothermic peak appeared when the reaction was carried out for 6 h, and the higher the temperature, the shorter the time span between the initial hydration stage and the first peak. A second hydration exothermic peak may occur when hydration continues to 1: 12 h. At the same hydration temperature, the hydration heat release rate of alkali-activated slag / fly ash cement is accelerated with the increase of slag content and the increase of water glass modulus. The kinetic calculation of hydration shows that the apparent activation energy also changes with the different ratio. The autogenous shrinkage of slag / fly ash cement excited by NaOH is relatively small, and that of water glass is larger. With the increase of the sodium silicate modulus, the self-shrinkage decreases and the rate of change slows down gradually in the range of 0.5 ~ 1.5 of sodium silicate modulus. At the same water glass modulus, the self-shrinkage decreases with the decrease of slag content. The drying shrinkage of alkali-activated slag / fly ash cement decreases with the increase of slag content and increases with the increase of water glass modulus. The regression equation of exponential function fits the curve of dry shrinkage with age and can effectively predict the drying shrinkage of different ages. With the decrease of slag content, the mass loss of alkali-activated slag / fly ash cement increases continuously within 56 days. The dry shrinkage value of slag / fly ash cement stimulated by NaOH is linearly related to the mass loss, and the bigger the slag content is, the bigger the straight line slope is. The shrinkage reducing agent mixed with oxidized enol has obvious effect on reducing drying shrinkage of alkali-activated slag / fly ash cement mortar, but the effect of magnesium oxide expansion agent is a little poor.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TQ172.1
本文编号：2182788
[Abstract]:Alkali-activated cementing materials have the characteristics of early strength and high strength, low heat of hydration, good corrosion resistance to acid and alkali, strong corrosion resistance to chloride ions and good resistance to seepage and freezing, but they also have such characteristics as fast solidification and large shrinkage. It is easy to produce cracks and potential alkali-aggregate reaction hazards and so on. The cracking of concrete caused by shrinkage will affect the durability, which is the main reason that restricts its application and development. The hydration and shrinkage properties of alkali-activated cementitious materials are influenced by many factors, such as the properties of the gelling components and the types and contents of the activators. The addition of fly ash has great influence on hydration development and shrinkage deformation. The alkali-activated slag / fly ash cement with good proportioning design can reduce the cost and improve the molding quality while ensuring the strength, but the research on its hydration and shrinkage characteristics is not systematic. The purpose of this paper is to study the effects of water glass modulus, slag content and temperature on the hydration heat release characteristics of alkali-activated slag / fly ash cement in Me2O / MeO / Me2O3 / SiO2 and Me2O Me2O3 / SiO2 / H _ 2O systems, and to analyze and characterize their kinetics. At the same time, the influencing factors and the law of autogenous shrinkage and drying shrinkage were studied, and the best way of reducing shrinkage was explored. The results show that the hydration heat release rate of alkali-activated slag / fly ash cement is different in different hydration stages. In the early stage of hydration, calcium and silicon ions in slag and fly ash were gradually dissolved, while water glass was hydrolyzed to form NaOH and Si (OH) _ 4. The first hydration exothermic peak appeared when the reaction was carried out for 6 h, and the higher the temperature, the shorter the time span between the initial hydration stage and the first peak. A second hydration exothermic peak may occur when hydration continues to 1: 12 h. At the same hydration temperature, the hydration heat release rate of alkali-activated slag / fly ash cement is accelerated with the increase of slag content and the increase of water glass modulus. The kinetic calculation of hydration shows that the apparent activation energy also changes with the different ratio. The autogenous shrinkage of slag / fly ash cement excited by NaOH is relatively small, and that of water glass is larger. With the increase of the sodium silicate modulus, the self-shrinkage decreases and the rate of change slows down gradually in the range of 0.5 ~ 1.5 of sodium silicate modulus. At the same water glass modulus, the self-shrinkage decreases with the decrease of slag content. The drying shrinkage of alkali-activated slag / fly ash cement decreases with the increase of slag content and increases with the increase of water glass modulus. The regression equation of exponential function fits the curve of dry shrinkage with age and can effectively predict the drying shrinkage of different ages. With the decrease of slag content, the mass loss of alkali-activated slag / fly ash cement increases continuously within 56 days. The dry shrinkage value of slag / fly ash cement stimulated by NaOH is linearly related to the mass loss, and the bigger the slag content is, the bigger the straight line slope is. The shrinkage reducing agent mixed with oxidized enol has obvious effect on reducing drying shrinkage of alkali-activated slag / fly ash cement mortar, but the effect of magnesium oxide expansion agent is a little poor.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TQ172.1
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