Grant-in-Aid for Scientific Research (C)
|Allocation Type||Single-year Grants|
|Research Institution||Fukuoka University|
SOEDA Masashi Faculty of Engineering, Fukuoka University, Research Associate, 工学部・土木工学科, 助手 (50148871)
HONDA Satoru Faculty of Engineering, Fukuoka University, Research Associate, 工学部・建築学科, 助手 (70181550)
EMOTO Yukio Faculty of Engineering, Fukuoka University, Associate Professor, 工学部・土木工学科, 助教授 (50090882)
SHIIBA Hiroyuki Faculty of Engineering, Fukuoka University, Professor, 工学部・建築学科, 教授 (30103782)
YAMATO Takeshi Faculty of Engineering, Fukuoka University, Professor, 工学部・土木工学部, 教授 (90078650)
|Project Period (FY)
1994 – 1996
Completed(Fiscal Year 1996)
|Budget Amount *help
¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1996 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1995 : ¥400,000 (Direct Cost : ¥400,000)
|Keywords||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|
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
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