Domestic carbon dioxide emissions are gradually on the rise. The main source of CO2 emission in the construction industry comes from cement production, especially during clinker making. The rise of CO2 emission is one of primary causes of global warming and we need to find ways reduce CO2 emission.
In the construction industry, it is supposed to use fly ash, which is an industrial by product, in order to reduce emission of CO2 generated by cement production. Using fly ash in cement increases the durability and chemical resistance of concrete, but there are two significant problems:
one is unburned carbon particles remaining in with the fly ash without burning at the power plant. The unburned carbon in fly ash will absorb the AE agent and deteriorate the fluidity of concrete; and
two is the amorphous film on the surface of fly ash particles formed for the duration of the quenching process during dust collection. This film interferes with reactive substances eluting from within fly ash particles. Such amorphous film is readily destroyed in alkaline environment and many of the studies on alkaline activators were conducted. However, alkaline activators are expensive and have many dangerous factors in use.
To resolve this problems of using fly ash, many researches were conducted on improving fly ash surface using CCP(Capacitively Coupled Plasma)type O2 plasma. But, employing plasma not only requires an expensive equipment but also the equipment produces CO2 and O3 when O2 is added as activated gas.
Therefore, in order to supplement existing problems with plasma and propose new methods to improve the surface of fly ash, this study used arc discharge for fly ash surface treatment. The changes in physical and chemical properties were tested about surface treatmented fly ash, and hardened cement mixed with surface treatmented fly ash, conducted SEM analysis for 3 and 7-day.
The result show that arc discharge treatment fly ash surface and removed the unburned carbon and reduced ignition loss. Moreover, the fineness increased as the particle size decreased as some particles were shattered. Cement matrix made of arc discharged fly ash displayed higher flexural and compression strength and had high content of hydrate when SEM analyzed compared to cement matrix mixed with normal fly ash. This is most likely due to the fact that arc discharge not only removed amorphous film but also the increased fineness improved fly ash reactivity.
It is determined that treatment the fly ash surface using arc discharge will not only facilitate obtaining the fluidity by removing the unburned carbon from the surface but also reactivity will be improved by removed film and increased fineness.