Abstract
The cement industry emits large amount of CO2. Blended cement is effective in CO2 reduction because 60％ of the CO2 is emitted by burning limestone. But blended cement has the problems which are decrease of early age strength and resistance to neutralization. It is thought that the problems are resolved by increasing alite（C3S）and free lime（f.CaO）. f.CaO and blended material has influence on hydration and fluidity. This paper discusses the influence of f.CaO and blended material on the early age hydration and fluidity of blended cement.
In case of cement without blended material, the increase of f.CaO caused decrease of fluidity. Ca（OH）2 was generated by hydration of f.CaO. The Ca（OH）2 increased the specific surface area and decreased the amount of superplasticizer adsorbing on a unit area. It was thought that the decrease of fluidity caused by decreased the amount of adsorbed superplasticizer. The fluidity was improved by blending fly ash（FA）or blast furnace slag（BFS）. In case of the cement that includes much f.CaO, FA was more effective than BFS. It was considered that the improvement was caused by dilution effect of blended material which decreased hydration product. There was an upper limit of f.CaO. In this research, the limit was 2％.
