| In recent years, the durability of reinforced or prestressed concrete structures has become a main concern, since engineers have to take into account the required service lifetime when selecting the concrete mixture and performing the structural design. A key parameter in durability predictions is the microstructure of the surface zone of concrete structures, i.e. the 'covercrete', more in particular the connectivity of the pores of the cement paste matrix. The major challenge of modern material science is the coupling of macroscopic materials properties to fundamental laws and mechanisms in force on lower levels, i.e. the meso-, micro- and nanolevel and even the molecular level. The evolution of the connectivity of the solid is the basis for the evolution of the mechanical properties, whereas the depercolation of the liquid phase, i.e. the formation of the pore structure, is the basis for the transport properties. Transport properties are the basis for durability models. The key objectives of this proposal are: - Improving the reliable and accuracy of microstructural models of cement-based systems made with blended cements, i.e. Portland cement with partial replacement of the cement with chemically active or inert fillers like fly ash, limestone powder, blast furnace slag, silica fume, and with admixtures. - Manipulating the connectivity of the pore structure of these systems by changing the blending proportions with the aim to influence the transport properties of the system. - Developing criteria for connectivity of virtual pore structures. This research aims at a fundamental improvement of our understanding of the effect of the use of active and inert powders as replacements of cement and of the effect of admixtures on the pore structures and on the connectivity of cement-based materials. Meanwhile, it will provide a solid basis for decision-making concerning mixture composition, curing methods of concrete in view of enhancing durability of concrete structures made with traditional and advanced types of concrete. |
