2011 Volume 65 Issue 1 Pages 14-19
Because of the vast utilization of industrial wastes and by-products in cement plant, it is necessary to control the fluidity of cement containing large amount of aluminate phase. In this research, we investigated the effect of fluidity by the addition of free-lime. Cement clinkers were synthesized from industrial raw materials and reagents by using an electric furnace in laboratory. The aluminate phase and F-CaO content for the synthesis of clinkers were varied 9％ & 12％ mass, and 0.24 & 0.31％ mass respectively. Cement samples were prepared by the addition of hemihydrate gypsum and dihydrate gypsum to clinker by adjusting the SO3 and hemihydrate-gypsum rate to 3％ and 50 mass％ respectively. Then, cement pastes were prepared by the addition of polycarboxylate type superplasticizer under water-cement ratio was 0.32. The apparent viscosity of the cement pastes was measured with a concentric-cylinder type rotational viscometer. The fluidity of the cement paste containing aluminate phase of 12 mass％ increased with increasing amount of f-CaO, reached maximum at 1％ of f-CaO. More than 1％ of f-CaO, the fluidity of the cement paste decreased. The fluidity of the cement paste containing aluminate phase of 12 mass％, and f-CaO of 1％ was further increased by replacing the cement paste with 5％ limestone-powder（LSP）. This enhancement in fluidity may be due to the presence of LSP and f-CaO in cement paste, which control C3A’s hydration. The fluidity of LSP containing cement paste（12％ mass）is nearly same as the fluidity of the cement paste containing 9 mass％ aluminate phase without LSP. In this study, apparent viscosity of cement pastes was not correlated to the heat generation rates of the cement pastes.
