高性能混凝土抗硫酸盐侵蚀试验研究

【作者】 乔宏霞；

【导师】 刘翠兰； 何忠茂；

【作者基本信息】 兰州理工大学 ， 结构工程， 2003， 硕士

【摘要】 耐久性是高性能混凝土最重要的指标，当今有关混凝土耐久性国内外已有大量的研究报导，并不断取得新成果和新经验，对改善混凝土耐久性提出了若干有效的方法。但是随着材料工程的发展，使用条件的苛刻，有很多重大问题仍远未解决，其中关键问题之一是混凝土耐久性能的评价和耐久性指标的选择。 本论文通过加入不同比例和不同种类的优质活性矿物掺合料、高效减水剂配制了适用于盐渍土地区的高性能混凝土，并针对盐渍土地区自然环境特点设计了混凝土耐久性的试验方法。 本文采用水中干湿循环、两种不同浓度的硫酸盐溶液中干湿循环的实验方法来研究混凝土抗硫酸盐侵蚀性。混凝土在盐溶液中干湿循环耐久性劣化速度比在水中干湿循环更快，随着盐溶液中硫酸根浓度的增加耐久性劣化速度加快，用盐溶液中干湿循环试验来评价混凝土抗硫酸盐侵蚀耐久性更为严酷苛刻，评价结果更为可靠。 本试验的混凝土分别以粉煤灰、矿粉、硅粉、复合粉煤灰作为掺和料进行试验研究，在普通强度等级的条件下实现了高抗硫酸盐侵蚀性能；试验结果说明粉煤次、矿粉B以及复合粉煤灰作为辅助胶凝材料能够极大地提高混凝土的耐久性能。 通过对混凝土耐久性能各项指标的评价，本论文认为混凝土的动弹性模量更为可靠和敏感，更能说明混凝土耐久性，说明用无破损检测方法评价混凝土的耐久性能是可行的；混凝土动弹性模量损失率达到40％认为丧失耐久性是可靠的。 本文通过扫描电子显微镜研究了高性能混凝土的微观结构，认为盐渍土地区高性能混凝土应比一般环境下的混凝土具有更趋完善的如下显微结构： (1)水泥石基体：水化产物C-S-H凝胶交织形成致密网状结构，硬化后期二次水化产物填充在其中，形成均匀致密的水泥石基体。 (2)界面区：除了具有一般环境下高性能混凝土所具有的界面过渡区厚度减小，水化产物生长取向度降低等特征之外，应更加注重界面区孔结构细化及界面区水化产物形成网状结构。 正是如上显微结构赋予盐渍土地区高性能混凝土优异的耐久性。更多还原

【Abstract】 Durability is one of the most important properties to evaluate the quality of concrete. Lots of original achievements and experiences in this field have been reported. A great deal of sound suggestions to improve the durability of concrete has been proposed. Although materials science and technology have being highly developed, there are still many problems remained unresolved by now when concrete structures are exposed in severe environment, for example, the guideline selection and durability evaluation of concrete.In this paper, high performance concrete (HPC), which are specially suitable for being used in salted region, are compounded with the differ proportion and kinds of mixing superplasticizer and high-quality mineral admixtures. In view of the environmental features of salted region, several different test methods of durability of concrete are designed.The paper studied sulphate resistance of concrete by drying-wetting in differ PH indicator salt solution and in water. Concrete durability deteriorates more rapidly under drying-wetting in salt solution than in water. And it is stricter to evaluate the frost resistance of concrete with the method of drying-wetting in salt solution than in water, and the evaluating results are more reliable.In the test of concrete, fly ash, mineral admixtures, silica fume and composite fly ash are for cement replacement materials (CRM). The results show that the high sulphate resistance of concrete has been completed in condition of general intension grade. The results show that fly ash, mineral admixtures and composite fly ash as CRM can increase concrete durability highly.After comparing the durability guideline, it is sure that dynamic elastic modulus is the most reliable to concrete durability; the method without dilapidation is feasible to evaluate concrete durability. It is sure that concrete lose durability when dynamic elastic modulus loss rate reached 40%.Through studying SEM microstructure of concrete, it is put forward that HPC used in salted region should form more perfect microstructures as the follows than the ordinary HPC:(1) Matrix of hardened cement paste: gel C-S-H forms dense net structure which is filled by secondary hydrate, so the matrix of hardened cement paste is very uniform and dense.(2) Interface zone: not only the thickness of interface zone is reduced and the orientation of hydrate in it decreases, but also its pore structure becomes better and hydrate in it forms net structure.It is the above microstructures that give the excellent durability to HPC used in salted region.更多还原