Volcanic tuffs from Hesse (Germany) and their weathering behaviour

摘要

In the Hessian region of Germany numerous deposits of tuffs are known from which natural building stones were extracted. Many buildings show examples of the use of this material in the past. In contrast to their attractive appearance and ease of extraction from quarries, tuffs are liable to destruction by weathering. Most common damages are disintegration, crumbling, cracking, scaling and flaking. In this paper, the causes of damage of selected varieties have been analysed using petrographical and petrophysical methods. The measured values are disadvantageous in comparison to other natural building stones. Large amounts of swellable clay minerals, mostly forming the cementing material, cause scaling due to repeated humidification. High porosity including negative pore structures and high adsorption effects results in structural damages while freezing. Consequently, most varieties of the described tuffs possess a limited usage as an outdoor building material.