抄録
It is well known that the fluidity and the setting time of fresh concrete are affected by kind and added timing of organic admixture including fluidizing agent, air entraining agent and water-re-ducing agent. The fluidity, setting time and time dependency of fluidity are measured using fresh cement paste prepared with four kinds of organic admixtures, polycalboxylic acid-based, aminosulfonic acid-based, β-naphthalenesulfonic acid-based and lignin sulfonic acid-based admixture, by two different methods of addition, that is, together with mixing water (simultaneous addition) and specified time after mixing with water (later addition). Hydration of cement, adsorptive behavior of organic admixture to clinker minerals, formation of calcium complex with organic admixture and flocculation structure of cement paste are also estimated with the state-of-the-art method such as Auger electron spectroscopy, X-ray photoelectron spectroscopy and environmental electron microscopy in order to clarify the influence of kind and added timing of admixture on the properties of fresh cement paste and concrete and elucidate the mechanism of the improvement of fluidity of cement paste and concrete in later addition of admixture.
