The Influence of Superplasticizers on the Dissolution of C3S

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Title: The Influence of Superplasticizers on the Dissolution of C3S

Author(s): T. Sowoidnich and C. Rößler

Publication: Special Publication

Volume: 262

Issue:

Appears on pages(s): 335-346

Keywords: dissolution; hydration; superplasticizers.

Date: 10/1/2009

Abstract:
The hydration of tricalcium silicate (C3S), the major component of portland cement, determines setting and strength of concrete. Setting of portland cement pastes (that is, concretes) is strongly affected by the use of superplasticizers (SP). As it is commonly agreed, the hydration of C3S proceeds through a dissolution precipitation process. Thus, the present study investigates the dissolution behavior of C3S in dependence of SP addition. Dissolution experiments are carried out at paste conditions (w/C3S = 0.5) and at high liquid-solid ratio (w/C3S = 50). It is shown that in the presence of SP the ionic concentrations in the solution are shifted to lower calcium and higher silicon values. The reason might be a varied degree of C3S hydration, complex formation, or shifted ion concentrations due to the presence of ions introduced by SP addition (that is, Na). Additionally, calorimetric analysis clearly shows that in the presence of SP the dissolution heat of C3S is increased. It is concluded that in the presence of SP the dissolution of C3S is not diminished but rather unchanged or even increased.