RÖRIG-DALGAARD, INGE1

1) Post doc, Technical University of Denmark, Department of Civil Engineering, ird@byg.dtu.dk

The main reasons for deterioration of bricks are frost, crystallization pressure and chemical exposure. Despite of this the effect of chemical exposure is no fully understood..

Depending on the brick type the original pH of bricks are 9-10. Though bricks can to subjected to water in shape of acid rain with a pH as low as 3. The exposure of acid rain and rain water on bricks is expected to have an influence on the brick matrix dependent on the specific exposure but to what extent? The present work is a systematic test of the influence of pH on the brick matrix using the effect of water with different well-defined pH values to examine the long term effect of acid rain or other reasons causing pH changes to bricks (as e.g. electrokinetic treatment).

Through capillary suction, macro pictures from the exposed surfaces, measurement of the pH and electrical conductivity it appears there is a consistence with the literature of the glassy phase describing ion exchange at low pH and break down of the lattice in the glassy structure at high pH.

Further work on polished sections with SEM/EDX, measurements of each of the ionic contents in the brick matrix and new tests with a longer exposure time to make more sound conclusions are anticipated.

Keywords: Brick matrix, pH, weathering