Correlation between surface forces and surface reactivity in the setting of plaster by atomic force microscopy

The setting of mineral binders cement, plaster, etc..arises as a direct consequence of surface reactivity by a process of dissociation and rehydration. This transformation induces a complete change of surface forces, of which the nature remains still unknown. The general process of the setting has been studied by means of plaster CaSO4P0.5H2O.crystals, chosen for an experimental convenience. The surface alteration growth, dissolution, atomic resolution.of the plaster crystal with respect to the introduction of the calcium sulfate solution has been followed by using atomic force microscopy AFM. Alternatively, this apparatus has been adapted by gluing a plaster microcrystal on the end of a microcantilever to quantitatively measure in situ the interactions between two plaster crystals in the condition of the setting. Kinetic comparison between force measurements and surface images leads to the conclusion of physical and chemical phenomena involved during the setting. q2000 Elsevier Science B.V. All rights reserved.