Carbonation of silicate-based minerals and industrial residues can help to reduce CO2 emissions as well as produce useful materials. However, until a full understanding of the chemistry and microstructural development of carbonation products is obtained. their utilization in engineering applications may remain limited. In respect of this, the present work examines microstructural properties of accelerated carbonated dicalcium silicate and Portland cement by using the complementary analytical techniques of XRD, SEM, TG-DTA, and NMR MAS. It was found that carbon dioxide reacts with calcium silicates to form calcite and aragonite and a polymerized silicate product comprised of cross-linked Q(3) co-ordinated silicon and fully polymerized Q(4) co-ordinated silicon. The extent of silicate polymerization was higher in carbonated dicalcium silicate, however, in the Portland cement-derived product, At Substitution in the Si-framework was detected. The amount of CO, that reacted with dicalcium silicate and Portland cement was 48 and 37% by mass, respectively. (c) 2006 Elsevier B.V. All rights reserved.