Effective utilization of fly ash as a by-product of coal-fired power plant is an issue. However, as the quality of fly ash fluctuates depending on the coal source, quality stabilization is required. Therefore, we studied development of quality stabilization technology for improving the quality by flotation method, and developed the unburned carbon removing device. Influence on hydration reaction and pore structure when curing temperature was changed was verified by cement paste with modified fly ash. The early age compressive strength increased with higher curing temperature, and there was no influence of fly ash. At long-term age, curing at 40℃ was promoted by the pozzolanic reaction to the greatest extent. And, Compressive strength showed higher strength of cement paste with fly ash. The relationship between the cumulative temperature and the compressive strength is difficult to estimate and evaluate the compressive strength at the cumulative temperature as the temperature curing becomes 80℃. Regarding the reaction rate of C3S, the modified fly ash showed the same level of reaction as Japanese Industrial Standard fly ash classII. However, the hydration rate of C2S of the modified fly ash was lower than the hydration rate of non-modified fly ash. The amount of calcium hydroxide was higher as the curing temperature was higher, and there was a difference from that without fly ash. The higher the curing temperature, the more pozzolanic reaction progressed at early age. The relationship between C-S-H and compressive strength was confirmed to increase in compressive strength with increasing C-S-H in a single specimen. If the kind of fly ash and curing temperature are different, amount of C-S-H is different even at the same level of compressive strength, so we could not estimate the strength. In the range of pore diameter 0.03~0.3μm, specimens with curing temperature 5, 20 and 40℃ increased with progression of the age. Whereas in the specimen 80℃ the specimens decreased. The influence of the amount of un burned carbon in fly ash is small on the pore structure.
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