Rheology of Cementitious Materials.
Rheology of Cementitious Materials.
(832 K)
Flatt, R. J.; Martys, N. S.; Bergstrom, L.
Materials Research Society (MRS Bulletin), Vol. 29, No.
5, 314-318, May 2004.
Keywords:
cements; rheology; concretes; colloids;
superplasticizers; polymers
Abstract:
The introduction of a new generation of dispersants in
concrete allow this material to exhibit self-compacting
properties in its fresh state and high durability and
mechanical strength in its hardened state. These
properties translate into many practical advantages for
the construction field.Two of the most important are
reducing the ecological impact of this sector of
industry and reducing the labor-intensive work
associated with placing ordinary concrete by vibration.
In this article, it will be shown that knowledge of
colloidal science has proven essential in the
development of this new generation of dispersants for
concrete. Indeed, the polymer molecules used in these
dispersants are specifically designed to induce steric
repulsion between cement particles, reducing their
agglomeration and allowing high workability of fresh
concrete prior to setting. While the linkage between
interparticle forces and the rheological behavior of
cement pastes is still only semiquantitative, recent
advances in the modeling of concrete rheology show very
promising results in terms of handling aggregates with a
wide distribution of particle sizes and shapes. However,
accurate modeling requires reliable input on the
interaction of the dispersant with the hydrating cement
at the molecular level, which is identified as a future
research challenge.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899