【作者】 刘伟宝；

【导师】 陆采荣；

【作者基本信息】 南京水利科学研究院 ， 材料学， 2008， 硕士

【摘要】 本文总结了碾压混凝土的发展过程和碾压混凝土筑坝技术的优势以及在北方寒冷地区的应用情况。阐述了含气量对于高寒地区碾压混凝土抗冻耐久性的重要性,说明了碾压混凝土含气量存在经时变化的事实。分析了水泥、粉煤灰、细骨料、粗骨料、外加剂和水对碾压混凝土含气量的影响,通过试验观察了碾压混凝土经时变化的规律。从失水、点面接触、表面张力下降和气泡迁移融合等角度分析了碾压混凝土含气量经时变化的机理。通过六组碾压混凝土含气量变化前后的性能对比试验,研究了含气量经时变化对碾压混凝土性能的影响。六组碾压混凝土包括三组二级配F300高抗冻碾压混凝土和三组三级配F50抗冻碾压混凝土,二种级配的碾压混凝土各考虑三种不同的骨料方案。对比了拌和后立即成型和静置30min后成型两种情况的混凝土拌和物性能、物理力学性能以及抗冻耐久性能,试验结果表明,静置30min后的碾压混凝土含气量有损失,物理力学性能略有提高,抗冻性能变化不大,但相对动弹性模量下降较快。采用直线导线法、数字图像分析法和RapidAir测试仪等三种方法测试计算气泡参数并进行对比,结果表明,静置30min后的碾压混凝土含气量损失、平均气泡半径减小而气泡间距系数增大。三种方法测出的气泡参数有偏差,从各种方法的原理分析认为RapidAir测试仪测得的结果可信度高。考虑将细骨料中的部分石粉或者全部石粉视为浆体成分,得出的碾压混凝土气泡间距系数变大。研究结果可为高寒干燥气候地区的碾压混凝土设计和施工提供参考。更多还原

【Abstract】 The history of Roller Compacted Concrete (RCC), the advantages of the technology of dam constructing using RCC and the application of RCC in northern cold areas were summarized. The importance of air-content to concrete anti-frozen durability was described, and the fact of the time-dependent air-content changing was pointed out. The influence of by cement, fly-ash, fine aggregate, coarse aggregate, admixture and water on the air-content was analyzed. The changing of air-content was observed through experiments. From different aspects such as the dehydration, the spot surface contact, the surface tension drop and the air bubble migration fusion, the mechanism of time-dependent air-content changing was analyzed. The influence of time-dependent air-content changing on RCC performance was studied by way of the comparative tests on air-content changed with the initial of 6 groups of RCC. The 6 groups of RCC included 3 groups of the second grade RCC of F300 and 3 groups of the third grade RCC of F50, each with 3 different types of aggregate. The property of fresh concrete, the physical and mechanical properties and frost-resisting durability of the initial one and that after 30 minutes were compared. The results showed that the air-content had certain loss, the physical and mechanical properties were improved, the frost-resisting durability had less change and the relative dynamic modulus of elasticity decreased fast after 30 minutes. The air void parameter was tested by three methods. The results showed that the air-content had certain loss, the average bubble radius decreased, and the air void spacing factor increased after 30 minutes. There were errors between the three methods but the changing trend was the same. The air void spacing factor would increase if the stone powder was partially or totally regarded as the cementitious material. It would be reference for the RCC design and construction in extreme cold and dry climate areas.更多还原