TRANSPORT ACROSS BRICK/MORTAR INTERFACE

In masonry brick and mortar are bonded, which is essential to its structural behaviour. Often it is assumed that a perfect hydraulic contact exists between mortar and brick. Simulations of the moisture transport in masonry transport are made accordingly. In order to verify this assumption, preliminary absorption experiments were performed on brick/mortar samples. The water absorption was measured from brick to mortar and the opposite, from mortar to brick. In figure 1 and 2 some typical profiles are presented. Because of the relatively large moisture diffusivity of the brick in comparison to that of the mortar, two situations can be distinguished. In the case of absorption from brick to mortar, moisture profiles start to develop in the mortar when the water reaches the interface. Since the mortar absorbs water rather slowly, the brick is quickly saturated up to its capillary moisture content. In the case of absorption from mortar to brick, the water is quickly absorbed by the brick when it reaches the interface, and after a few hours an almost stationary moisture profile develops in the mortar.

Figure 1: Moisture profiles measured during the absorption of water in a sample of fired- clay brick (GH) and mortar without air-entraining agent (MZ). The experiment lasted 6 hours for absorption from brick to mortar. The shaded box indicates the interface area and the dashed line indicates the end of the sample. In this figure 22 profiles are plotted; after the first 10 profiles the time between subsequent profiles is of the order of 20 min.

Figure 2: Moisture profiles measured during the absorption of water in a sample of fired- clay brick (GH) and mortar without air-entraining agent (MZ). The experiment lasted 24 hours for absorption from mortar to brick. The shaded box indicates the interface area and the dashed line indicates the end of the sample. In this figure 34 profiles are plotted; after the first 10 profiles the time between subsequent profiles is of the order of 45 min

• An extensive description of these experiments can be found in:

L. Pel, Moisture transport in porous building materials, Ph.D. thesis, Eindhoven University of Technology, the Netherlands (1995).

H.J.P. Brocken and L. Pel, Moisture transport over the brick/mortar interface, International synposium on moisture problems in building walls, 415-424, Sept 11-13, Porto, Portugal (1995).

L. Pel, K. Kopinga and H. Brocken, Determination of the moisture transport over brick/mortar interfaces by NMR, 9. Feuchtetag, Sept 17/18, Weimar, Germany, 66-75 (1997).

H.J.P. Brocken and L. Pel, Moisture transport over the brick-mortar interface: water absorption and drying, Proc. 11th Int. Brick/Block Masonry Conf., Oct. 14-16, Shanghai, China, 826-835 (1997).

H. Brocken, L. Pel and K. Kopinga, Moisture transport over the brick/mortar interface,  Nuclear Magnetic Resonance Spectroscopy of Cement Based Materials (edited by P. Colombet, A.R. Grimmer, H. Zanni and P. Sozzani), Springer Verlag, Berlin/Heidelberg, Germany (1998).
 

  Back to main page

Last updated : 15-01-1998