DOUBLE MIXING EFFECTS EXERTED BY VARIOUS COMBINATIONS OF MIXING SEQUENCE FOR THREE COMPONENTS

It has been found that bleeding of fresh cement paste is remarkably changed by divided addition and subsequent divided mixing of water for the same mix proportion. This method is called double mixing and referred to as DM hereinafter, compared to the coventional method referred to as SM. Bleeding of DM paste manufactured with the optimum primal water proportion is decreased to about one-fifth for ordinary Portland cement.In this paper, DM effects exerted by various combinations of mixing sequence for three components, where superplasticizer (SP), polymer dispersion or another powder, such as fly-ash, blast furnace slag or silica fume is added as the third component, were experimentally investigated. The main conclusions in this paper are summarized as follows; (1) In DM with SP, DM effects were normal only when SP was added at the first stage mixing and that the bleeding of DM paste manufactured with the optimum amount of SP could be minimized. (2) In DM with polymer dispersion, bleeding and segregation of polymer particles can be decreased. (3) In DM with silica fume, the optimum primal water proportion is decreased by its micro filler effect. As a whole, DM can be utilized for mixing of three components.