2019 Volume 57 Issue 8 Pages 565-573
In this paper, the phenomenon whereby fresh concrete undergoes significant loss of flowability when it is allowed to stand undisturbed for a while, which is a problem in construction work, is referred to as “stiffness”, and the stiffness generation mechanism is hypothesized based on microscope images of cement paste. The authors developed a chemical admixture (stiffness reducing agent) that suppresses the flocculation of cement particles and verified its effect through various tests. Through verification tests, we sought to quantify the degree of stiffness of concrete by a simple test called the vane shear test. Further, through various workability tests, we confirmed the possibility that stiffness may affect actual construction work, and we introduce construction cases where application of stiffness reducing agent improved filling performance in high density rebar areas and workability in lining work of fiber reinforced concrete.
