Synchrotron nanoprobe X-ray fluorescence maps show for the first time discrete iron-rich, titanium-rich and manganese/silicon-rich particles present in blast furnace slag grains, and these particles remain intact when the slag is used as a precursor for alkali-activated slag (AAS) binders. These particles appear to be entrained during slag production, and remain stable under the reducing conditions prevailing during alkali-activation. There is no evidence of chemical interaction between these particles and the AAS binder, which mainly comprises calcium silicate hydrates. These results are important for the understanding of iron chemistry in AAS, and the potential reactivity of metallic and other redox-sensitive species within AAS binders. (C) 2014 Elsevier B.V. All rights reserved.