Cementitious Materials

Nanostructures

© Photo Fraunhofer SCAI

The nanostructure of cementitious materials forms in dependence on its mixture at binding time. Since this process requires several days in real time, it has not been accessible to simulation on the nano scale.

Using high efficient implementation of reactive potentials and modern »replica exchange« methods, such processes are accessible to the Tremolo-X software and can be used to predict the structure of the basic builidng blocks in cementitious materials.

High performance cementitious materials

© Photo Fraunhofer SCAI

Cement and cementitious materials are of paramount importance in todays society. In light of their widespread use in the construction of bridges, airport, average homes and countless other keycomponents of modern infrastructure their stability and reliability is of uncomparable significance.

However, it is well known that the leeching of ions has a destabelizing effect on those materials, a process which is accelerated by industrial exhaustion and acidic rain - everyday occurances in urban centers.

With this background in mind it may come as a surprise that many fundamental questions to cement and cementitious materials have not yet been answered by science.

For one there is no reliable knowledge about the nanostructure, the basic builidng blocks of cementitious materials. Furthermore there is still a lack of models describing the progression of ion leeching from the cement matrices.

The Department of Virtual Material Design of Fraunhofer SCAI supplies tools, which solve such problems.

Ion leeching

© Photo Fraunhofer SCAI

The leeching of ions from the cement matrix is a coupled transport-reaction process of multiple different ion species. The mathematical modeling of the transport by the Poisson-Nernst-Planck equation system ist generally known, however, numerical software which has the ability to solve those coupled equations for multiple species in physical geometries were missing up to date.

The NPNP software uses modern iteration techniques and implicit discretization to close this gap and allow a prognosis of the sensitivity of cementitious materials with respect to ion degradation.

References

  1. J. S. Dolado, M. Griebel, J. Hamaekers, and F. Heber. The nano-branched structure of cementitious calcium-silicate-hydrate gel. Journal of Materials Chemistry, 21:4445-4449, 2011.
    [ bib ]
  2. H. Manzano, J. Dolado, M. Griebel, and J. Hamaekers. A molecular dynamics study of the aluminosilicate chains structure in Al-rich calcium silicate hydrated (C-S-H) gels. physica status solidi (a) - applications and materials science, 205(6):1324-1329, 2008.
    [ bib, note ]
  3. J. S. Dolado, J. Hamaekers, and M. Griebel. A molecular dynamics study of cementitious silicate hydrate (C-S-H) gels. Journal of the American Ceramic Society, 90(12):3938-3942, 2007.
    [ bib, note ]