Structural Description of Cement Hydrates Modified by Incorporation of Nanocomposites Derived from Lamellar Double Hydroxides

Calcium silicate hydrates (C-S-H) are the main phases resulting from the hydration of anhydrous Portland cement and on which the evolution of mechanical properties depends. This paper examines the mineralogy and structure of C-S-H in the presence of calcined Lamellar Double Hydroxides (LDH) based on Zn, Al and Ti. This nanocomposite was synthesized with success by the direct coprecipitation method and characterized by XRD. Different samples were prepared and characterized: clinker pastes with mixed oxides CZnAlTi varied from 0 to 5% by weight with a water/cement ratio of 0.4. The semi-quantitative analysis by XRD indicated that the basic elements of the synthesized powder interact in the C-S-H phases which come in different forms containing Al and Zn. The structures of the different C-S-H formed in the various clinker pastes have been presented. This part was focused on the drawn models describing the structural changes of C-S-H at the crystallographic level as a function of the calcium/silicon (Ca/Si) ratio and the incorporated Zn and Al elements. The structures were then interpreted and compared to correlate the structural changes of C-S-H. The results showed that the C-S-H phases having the highest Ca/Si ratios have the shortest octahedral calcium chains and therefore the interlayer spaces are smaller.