Résumé:
One of the basic characteristics that self-compacting concrete (SCC) possesses is resistance to
segregation; the mix is homogeneous through its placement and hardening. Poor resistance to
segregation will be manifested by internal and external water leakage, accumulation of lighter
components, a paste-rich layer forming at the top, and coarse aggregate settling at the bottom.
Such imbalances may grossly compromise the long-term structural integrity of the concrete. A
few of the key factors determining the potential for aggregate sedimentation include mix
viscosity, size, and density of the aggregates, along with flow rate. To be effective, the SCC
needs to retain homogeneity throughout the mix in retaining required mechanical properties.
This paper presents the cylinder-column segregation test for monitoring static segregation
with time in both fresh and hardened states of SCC. Concretes containing different amounts of
viscosity modifying agent (VMA) were prepared to investigate the effectiveness of viscosity
modifying agent (VMA) in enhancing the rheology and stability of SCC mixtures. In this
respect, the study concerns the understanding of the aptitude of VMA to influence important
parameters such as slump flow, flow time, and time of flow in a diameter of 500 mm and
resistance to vertical segregation. Other issues related to the study include the determination
of the long-term VMA effects on compressive strength and tensile strength by testing the
cured concrete.
The segregation test of the cylinder column is very important, as it determines and quantifies
the static segregation within the mixtures of SCC. This test provides a direct and quantitative
determination of stability in regard to the fresh state of concrete. More specifically, the
experiment calculates the contents of coarse aggregate above 8 mm in a specimen that is 300
mm high in time lapses of 15, 30, and 45 minutes after casting. These sedimentation tests
conducted provide a clear picture of segregation with regard to time through the cylindercolumn
segregation test. Additions of VMA have shown immense improvements in the
rheological properties of SCC, hence improving segregation resistance and thereby improving
both compressive and tensile strengths compared to a reference mixture without VMA. This
underlines the favorable role of VMAs for better overall performance in SCC.
