Activated slag cement (ASC) shows significantly higher shrinkage than ordinary Portland cement agglomerates. Cracking generated by
shrinkage is one of the most critical drawbacks for broader applications of this promising alternative binder. This article investigates the
relationship between ASC hydration, unrestrained drying and autogenous shrinkage of mortar specimens. The chemical and microstructure
evolution due to hydration were determined on pastes by thermogravimetric analysis, conduction calorimetry and mercury porosimetry. Samples
were prepared with ground blast furnace slag (BFS) activated with sodium silicate (silica modulus of 1.7) with 2.5, 3.5 and 4.5% of Na2O, by slag
mass. The amount of activator is the primary influence on drying and autogenous shrinkage, and early hydration makes a considerable
contribution to the total result, which increases with the amount of silica. Drying shrinkage occurred in two stages, the first caused by extensive
water loss when the samples were exposed to the environment, and the second was associated with the hydration process and less water loss. Due
to the refinement of ASC porous system, autogenous shrinkage is responsible for a significant amount of the total shrinkage.