Effect of Cement Kiln Bypass Dust on Properties and Hydration of Akali-Activated Slag Mixtures

During recent decades, alkali-activated slag (AAS) systems have attracted great scientific interest
around the world. Despite many efforts its severe shrinkage and cracking is still a delicate issue. The
aim of this work was to partially replace slag by cement kiln bypass dust (CBPD) which, on the basis of
its mineralogical composition, would act as an expansive agent (EA) and thus compensate AAS
shrinkage. It was observed that volume changes of AAS/CBPD mixtures strongly depended on CBPD
dose since low slag replacement levels did not significantly reduce autogenous shrinkage while around
50% of CBPD or more led to severe expansion. Based on X-ray diffraction, this expansion is related to
hydrocalumite-type phase formation. The presence of CBPD also totally modified calorimetric
response of AAS pastes.