Finally, XRD experiments (Figure ) were carried out to better study the crystalline phases formed during hydration. Very different products precipitated depending on the activator used. Indeed, even though a very broad diffuse peak around 30° attributed to amorphous C-A-S-H appeared in the diffractogramms of all samples, hydrotalcite was only visible in NaOH-activated samples, while calcite and then gaylussite formed in the Na2CO3-activated slag pastes.