Accélération de ciment au laitier par du ciment sulfo-alumineux

ABSTRACT
The use of supplementary cementing materials such as blast furnace slag, in cements
contributes to reduce their environmental impact. The industrial development of slag cements is
slowed down by their limited early-age mechanical performances and high drying shrinkage. The
present study deals with the acceleration of two slag cements: a slag cement CEM III A and a slag
cement containing 83,5% blast furnace slag and 15,5% anhydrite. The acceleration results of the
partial replacement of slag cement by calcium sulfoaluminate cement. The hydration of calcium
sulfoaluminate cement yields ettringite which allows the cement to develop high early strength.
Furthermore, drying shrinkage is limited.
The presence of Portland clinker in the slag cements is responsible of quick setting time and
quick hardening of the mortar due to the activation of yeelimite, the main component of calcium
sulfoaluminate clinker, by portlandite yielded by the hydration of calcium silicate phases. To
compensate the limited time of workability, some setting time retarders are introduced but they
reduce the medium-term mechanical performances. The presence of Portland clinker has
detrimental effect at early age, but increases the medium-term activation of slag and therefore leads
to an important improvement of strength.
The content of each component (slag cement, calcium sulfoaluminate cement and Portland
clinker, and calcium sulphate) is optimized by the evaluation of mechanical performances. To
follow the process of hydration of binders, XRD and DTA-TGA analyses have been carried out on
cement pastes.
TITLE :
Acceleration of slag cement by calcium sulfoaluminate cement
KEY-WORDS :
slag cement, calcium sulfoaluminate cement, acceleration, activation, drying shrinkage,
microstructure.
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