Fly ash in concrete is known to be effective in improving workability, the reduction of heat of hydration, increasing the long-term strength, and improving durability. Recently, fly ash is considerd an essential material for the high-strength concrete. However, there are only little research for the high-strength fly ash concrete in Korea even though the fly ash is produced about 2 million ton a year.
In this paper, investigation for the strength and workability characteristics was carried out when fly ash was used in the high-strength concrete.
Selected test variables were compressive strength with 6 levels (2 levels of normal strength and 4 levels of high-strength) and fly ash contents(0, 10, 20, 30%). Specimens were tested for compressive strength at 3, 7, 28, 90 and 180 days with 3 cylinders for each age. Slump of highstrength fly ash concrete was controlled to 20±2cm with superplasticizer.
As the result, fly ash was effective in increasing the long-term compressive strength, but the short-term compressive strenght was gradually decreased with increasing fly ash contens. And also the use of superplasticizer was required for providing the proper workability when fly ash contents were increased. The optimum content of fly ash was about 10%.
