Rheological Study of Superplasticized Concrete
K. Kishitani, F. Tomosawa,
and S. Oka
Appears on pages(s):
cement pastes; coarse aggregates; flow table tests;
grout; mortars (material); plasticizers; rheological properties;
slump tests; water-cement ratio; water-reducing agents; work-ability.
In order to consider the workability of superplasticized concrete, it is necessary first to evaluate rheologically the effect of a superplasticizer on fresh cement paste. The authors conducted a series of experiments measuring the resist-ances met by a sphere in motion at various constant speeds in cement pastes, and calculated their rheological constants. It is indicated that the rheological constant of a paste to which superplasticizer has been added is completely different from that of plain paste and also different from pastes with conventional chemical admixtures, and as a result, the superplasticizer can be rheologically defined. Further, in order to clarify the reason for the comparatively rapid slump loss after superplasticizing, the variations in rheological constants due to elapse of time after mixing of cement paste are measured, and it is found that when the addition of the superplasticizer is delayed, the increase in the yield value (rheological constant) is hastened, and it is thus substantiated that the rate of slump loss of concrete is increased when the timing of superplasticizer addition is delayed.