引气剂对混凝土流变性能及气泡特征参数的研究

发布时间：2018-12-30 15:30

【摘要】：随着对混凝土施工要求的不断提高和电子化的迅速发展,混凝土工艺不能只停留在经验性的阶段,从混凝土流变性理论上对混凝土性能进行研究和探讨十分必要和迫切,而引气混凝土是混凝土结构耐久性要求发展的必然方向。因此,开展引气剂对砂浆和混凝土流变性能影响与气泡特征参数影响的研究具有重要的实用价值和理论意义。研究了4种较有代表性的引气剂对砂浆流变性能的影响。结果显示,引气剂大幅提高了低流态砂浆的流动度,略微降低了高流态砂浆的流动度；随着含气量的增加,砂浆塑性粘度增大,低流态砂浆屈服应力降低,高流态砂浆屈服应力稍有提高,其中掺分子量较大的B引气剂时,屈服应力显著提高,流动度损失较大。以混凝土为研究对象,研究了引气剂对混凝土工作性和流变性能的影响。结果显示,引气剂显著提高了混凝土工作性,降低混凝土泌水率,提高了塑性混凝土坍落度,略微降低了高流态混凝土坍落度；随着含气量的增大,混凝土的塑性粘度得到了提高,塑性混凝土屈服应力稍有降低,高流态混凝土屈服应力没有明显变化。研究了引气剂对硬化混凝土强度和气泡特征参数的影响。结果表明,引气剂降低了混凝土抗压强度,略微提高了混凝土抗折强度,折压比显著提高。新拌混凝土含气量与硬化混凝土含气量存在一定的相关性,且当含气量小于8%时,随着含气量的提高,硬化混凝土气泡间距系数和气泡平均直径逐渐减小,气泡总数增多,当含气量大于8%时,有相反趋势。论文提出了评价引气剂品质的一些方法和指标。通过测定引气剂溶液的气泡容量和消泡时间与混凝土含气量损失试验可简单判定出劣质的引气剂,认为评价引气剂品质的最终方法应是测定其气泡间距系数,且采用气泡间距系数与新拌混凝土含气量比值来评价引气剂质量可能更为准确。
[Abstract]:With the continuous improvement of concrete construction requirements and the rapid development of electronization, concrete technology can not only stay in the empirical stage. It is necessary and urgent to study and discuss the concrete performance from the theory of concrete rheology. Air entrainment concrete is an inevitable direction for the durability of concrete structure. Therefore, it is of great practical value and theoretical significance to study the effect of air entraining agent on the rheological properties of mortar and concrete and the influence of bubble characteristic parameters. The effects of four representative air-entraining agents on the rheological properties of mortar were studied. The results show that the fluidity of low-flow mortar is greatly increased and the fluidity of high-flow mortar is slightly decreased by the air-entraining agent. With the increase of gas content, the plastic viscosity of mortar increases, the yield stress of low flow mortar decreases, and the yield stress of high flow mortar slightly increases. The effect of air entraining agent on the workability and rheological properties of concrete was studied. The results show that the air-entraining agent can significantly improve the workability of concrete, reduce the bleeding rate of concrete, increase the slump of plastic concrete, and reduce the slump of high-flow concrete slightly. With the increase of gas content, the plastic viscosity of concrete increases, the yield stress of plastic concrete decreases slightly, but the yield stress of high flow concrete does not change obviously. The effect of air entraining agent on strength and bubble characteristic parameters of hardened concrete was studied. The results show that the air entraining agent reduces the compressive strength of concrete, slightly increases the flexural strength of concrete, and increases the compression ratio significantly. There is a certain correlation between the air content of fresh concrete and the air content of hardened concrete. When the air content is less than 8, with the increase of air content, the coefficient of bubble spacing and the average diameter of bubbles in hardened concrete decrease gradually, and the total number of bubbles increases. When the gas content is greater than 8, there is a reverse trend. Some methods and indexes for evaluating the quality of air entraining agent are put forward in this paper. By measuring the bubble capacity and defoaming time of the air-entraining agent solution and the air content loss test of concrete, the inferior air-entraining agent can be simply determined. It is considered that the final method to evaluate the quality of the air-entraining agent is to determine the bubble spacing coefficient. It may be more accurate to evaluate the quality of air entraining agent by using the ratio of bubble spacing coefficient and fresh concrete gas content.
【学位授予单位】：河北工程大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528

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