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Effect of Mixing Method on the Freeze Thaw Dulability of Silica Fume Concrete

搅拌方式对硅粉混凝土冻融耐久性的影响

基本信息

批准号：
06650504
负责人：
SOEDA Masashi
金额：
$ 0.51万
依托单位：
Fukuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06650504/
关键词：
Silica Fume Mixing Time Air Content Surerplasticizer Pore Structure Air Void System Compressive Strength Water-to-cement ratio 養生方法積算温度品質比重・湿分活性度指数モルタルコンクリート

项目摘要

Using various types of silica fume colleted so far, the authors investigated the effects of the form and chemical components of silica fume on the fluidity of concrete with relation to material charging methods and mixing time. Freezing and thawing tests and air-void distribution measurements were also made on hardened concrete, for the purpose of total evaluation of the resistance to freezing from the aspects of the mixing method and air-void distribution.The results obtained in this paper are summarized as follows :1. The freezing resistance of non-AE concrete with a water-binder ratio of 35% or higher significantly decreases as the silica fume replacement ratio increases. The limit water-binder ratio to produce non-AE concrete judged as having high resistance to freezing is around 25%. Concrete with a higher water-binder ratio will require appropriate air entraining.2. The air content required to obtain sufficient resistance to freezing for silica fume concrete with a water-binder r … More atio of 55% is around 6% and 8% at a replacement ratio of 10% and 20%, respectively. The air content should therefore be increased by 2 to 4 percentage points when using silica fume.3. The void spacing factor increases as the water-binder ratio decreases. With the water-binder ratio at 35% or higher, the void spacing factor of concrete containing silica fume tends to be slightly higher than the case without silica fume.4. Silica fume concrete with an entrained air content of around 4% and a low water-binder ratio has high resistance to freezing independently of the mixing time. When the water-binder ratio is 55%, a difference in the mixing time leads to a wide difference in the durability factor, with the maximum being two times the minimum.5. The microstructure of hardened concrete is densified by the use of silica fume or a reduction in the water-binder ratio, but is scarcely affected by the mixing time.6. The use of silica fume reduces air-voids smaller than 200 ()m in diameter and increases air-voids larger than 500 ()m in diameter.7. The pore size distribution varies depending on the mixing time. The total number of air-voids in silica fume concrete is largest when it is mixed for 180 seconds. Also, the number of small-diameter voids increases and the void spacing factor decreases at this mixing time. Less

利用收集到的各种类型的硅灰，研究了硅灰的形态和化学组成对混凝土流动性的影响，以及与加料方式和搅拌时间的关系。本文还对硬化混凝土进行了冻融试验和气孔分布测试，从拌和方法和气孔分布两个方面对混凝土的抗冻性进行了全面的评价。本文的研究结果如下：1.随着硅灰掺量的增加，水胶比大于35%的非AE混凝土的抗冻性显著降低。生产被认为具有高抗冻性的非AE混凝土的极限水胶比约为25%。水胶比较高的混凝土将需要适当的引气剂。含水粘结剂r…的硅粉混凝土获得足够抗冻性所需的含气量当置换率为10%和20%时，55%的比率分别约为6%和8%。因此，使用硅烟时，空气含量应增加2至4个百分点。孔隙间距系数随着水胶比的减小而增大。当水胶比在35%或更高时，掺硅灰混凝土的空隙间距系数略高于不掺硅灰混凝土。掺气量在4%左右、水胶比较低的硅粉混凝土具有较高的抗冻性，且与搅拌时间无关。当水胶比为55%时，搅拌时间的不同会导致耐久系数的差异很大，最大值是最小值的两倍。掺加硅灰或降低水胶比可使硬化混凝土的微观结构致密化，但搅拌时间对其影响不大。硅灰的使用减少了直径小于200米的空隙，增加了直径大于500米的空隙。孔径分布随混合时间的不同而不同。硅灰混凝土掺入180s后，气孔总数最多。此外，在此混合时间，小直径空穴的数量增加，空穴间距因子减小。较少