Spezialfragen Bauphysik
Chair of Building Physics

 u p d a t e   Thursday, December 04, 2003

   

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AFM investigation of the formation of water layers on internal surfaces of porous building materials

Collaborator: Tianhe Yang, Dipl.-Ing.
Start: 05/2000

Contacts: T. Yang, B. Keller, E. Magyari

Nanostructure of cement Nanostructure of cement

Funds: TOP NANO 21

The combined transport of heat and moisture in porous building materials plays an important role for the durability of the materials and therefore also for the sustainability of the construction. Two basic properties of a material determine the transport properties for heat and moisture on the mesoscopic level:

 

  • the structure and topology of the free pore space,
  • the properties of the related surfaces or molecular structures of the material and their interaction with water molecules.

It is well known that moisture can be transported

  • by vapour diffusion,
  • as mono- to poly-molecular film on internal surfaces,
  • as capillary liquid.

To investigate the mono- to poly-molecular water film on internal surfaces, it is important to find ways to prepare micro particles from mostly polycrystalline building materials as brick, concrete and others. By means of the AFM technique we will later in a forthcoming fundamental research project study the building up of water molecular layers on such crystals.

An understanding of the specific role of the internal surfaces and their structure for the transport of water in building materials would open the door for a real understanding of these processes and further could be the base for a molecularly based design of materials with desired properties for heat and moisture transport. This could revolutionise the materials use in the building industry.

AFM microscope

The goal:

To understand and to qualitatively formulate the conditions for wetting of the internal surfaces of porous building materials.

Index terms:

 

 

AFM, moisture transport, wetting, internal surface, building material, building physics

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