抄録
Slump loss of concrete has been attributed ambiguously to the chemical hydration reaction. On the assumption that the physical coagulation of cement particles during the dormant stage is responsible for the slump loss to a large extent, the phenomenon was analyzed in this paper by the theory of colloidal coagulation.
From the results obtained, it was found that the half loss time of concrete slump (S1/2) or cement paste flow (F1/2) was approximately proportional to the time during which the particle number was reduced to a half of the initial (t1/2).
The technique of repeated partial dosing of superplasticizers applied in this test was found to be a useful way to keep slump for a long time. A newly developed automatic metering and injecting device installed on a truck agitator was quite effective to maintain the slump before placement.
