【作者】 林晖；

【导师】 高培伟；

【作者基本信息】 南京航空航天大学 ， 结构工程， 2006， 硕士

【摘要】 近年来,在改性混凝土的研究与应用中,纤维混凝土的地位越来越重要,目前工程应用中采用最多的有钢纤维、聚丙烯纤维和尼龙纤维等,聚乙烯醇纤维以其抗拉强度高、弹性模量高、耐酸、耐碱等特点逐渐受到人们的重视。本文围绕高性能混凝土在掺入聚乙烯醇纤维后的部分性能展开研究工作,研究内容包括:1)对新拌混凝土的工作性进行研究,发现在一定数量范围内的PVA纤维对高性能混凝土的工作性能无不良影响。采用新型分散工艺,并使用水洗法对纤维的分散性进行检验,发现纤维分散性良好。2)对PVA纤维混凝土的抗压强度、抗折强度、劈裂抗拉强度进行试验研究,发现PVA纤维对混凝土强度略有提高。3)提出了塑性PVA纤维混凝土凝缩机理模型和阻裂模型,探讨了其阻裂机理,其优良性能和它的亲水性不可分割。通过对PVA纤维混凝土的凝缩性能和塑性开裂性能试验研究发现,PVA纤维掺量在0.9 kg/m~3以内对凝缩具有明显的抑制作用,大于这个掺量,改善效果提高微小。掺量为0.9 kg/m~3的PVA纤维可以较好地抑制混凝土塑性裂缝的产生,塑性裂缝的数量少于掺等量PP纤维的混凝土。4)通过光学和电子显微镜对硬化PVA纤维混凝土的破坏机理进行研究,探讨了纤维断裂破坏的过程和纤维的阻裂机理。通过试验发现掺加PVA纤维可以减少混凝土的干缩,但改善效果与其掺量有关。掺PVA纤维混凝土在28d内的干缩值小于PP纤维;当PVA纤维掺量大于0.64kg/m~3时,混凝土出现了双缝和多缝开裂的特征;不同掺量的PVA纤维砂浆比基准砂浆、PP纤维砂浆的初始开裂时间迟,且掺量增加,开裂时间推迟。5)结合实际工程对PVA纤维的工程应用效果进行分析研究。更多还原

【Abstract】 In recent years, fiber concrete becomes more and more important in research and application of modified concrete. At present, the steel fiber, polypropylene fiber and nylon fiber are widely used in practices. The polyvinyl alcohol fiber which has high tensile strength, high elastic modulus and resistance to acid, alkali and solarization, has been used as a new reinforced material in concrete.This paper focuses on the performance of polyvinyl alcohol fiber reinforced concrete. The main contributions of this dissertation are summarized as follows:1) The workability of polyvinyl alcohol fiber concrete is studied in this paper, and the results show that the polyvinyl alcohol fiber has no negative effect in a certain range. Water-washing method is used to detect the dispersion performance of the polyvinyl alcohol fiber, and the results show that the dispersion performance is improved by new production process.2) The polyvinyl alcohol fiber in concrete can improve its’mechanical performance slightly, such as compressive, flexural and split tensile strength according to the relevant test results.3) The mechanism model of settlement shrinkage is proposed, and cracking resistance mechanism is discussed. This paper suggests that the excellent performance of polyvinyl alcohol fiber concrete is related to its’hydrophilicity. The polyvinyl alcohol fiber in concrete can decrease the settlement shrinkage value obviously if the content is not more than 0.9 kg/m~3. However, the polyvinyl alcohol fiber exceeding this dosage can not improve the value further. The plastic shrinkage cracks of concrete with 0.9 kg/m~3 polyvinyl alcohol fiber can be controlled excellently, and the amounts of them are less than that of concrete with polypropylene fiber at the same dosage. 4) The broken characteristics and the crack resistance mechanisms of PVA fiber in concrete are discussed by SEM and optical micrograph. Through experiments, it is found that dry shrinkage values of concrete can be decreased by blending PVA fiber depending on the dosage of PVA fiber in concrete. It is noted that the dry shrinkage value of concrete with PVA fiber is less than that of concrete with PP fiber in the period of 28 days. The features of two or more cracking appear when the dosages are more than 0.64kg/m~3, and the initial cracking time of PVA fiber concrete in ring test is later than that of the concretes without fiber or with PP fiber. The cracking time of concrete is delayed when the dosage of fiber in concrete increased.5) The effects of PVA fiber on the practical project of concrete were investigated at the same time.更多还原