Abstract
The material design of high aluminate phase cement containing mineral admixtures is expected to become important in the future, in order to balance the expanding waste usage and the reduction of CO2 emission. In this study, we investigated the influence of mineral admixtures on the paste fluidity and hydration properties of cement having high aluminate phase content. Cement clinkers were synthesized from industrial raw materials and reagents by using an electric furnace in laboratory. The aluminate phase contents of clinkers were about 9mass％ and 12mass％ with unchanging C3S content. Cement samples were prepared by adding calcium sulfate to clinker adjusting the SO3 content to 2％ or 3％, and by adding granulated blast－furnace slag and limestone powder. The amount of mineral admixture in the samples was set to 15mass％. Cement pastes were prepared adding polycarboxylate type superplasticizer under water－cement ratio was 0.32. The apparent viscosities of the cement pastes were measured with a concentric－cylinder type rotational viscometer. Furthermore, the rate of heat liberation, hydration products, and immobilization capacity of Cr6＋ were evaluated. The fluidity of the cement paste was varied according to the blend ratio of blast－furnace slag and limestone powder. It was clarified that the fluidity of the cement paste could be improved by adding more than 5mass％ of limestone powder when the C3A content of cement was increased from 9 to 12mass％. For the hydration properties, the hydration products of aluminate phase were found to be systematically－varied according to the mix proportion of mineral admixtures. This result indicates that blending condition of blast－furnace slag and limestone powder could also influence on immobilization capacity of various elements such as hexavalent chromium.
