Sandstone degradation: an experimental study of accelerated weathering

摘要

The investigated rock material belongs to the group of upper cretaceous quader sandstones which are very important construction stones in Poland and Germany. The mineral composition of the rocks is relatively uniform—they are quartzose sandstones. The most important feature is their good workability and comparatively high weathering resistance. Still, regardless of the apparent resemblance, the observations carried on buildings and monuments show differences in weathering processes. The undertaken test was an attempt to verify the proposed before rock classification, performed on the basis of parameterization of porosimetric cumulative intrusion volume curves. The aim of the experiment was the evaluation of the sandstone petrography (including the structure, texture and porosity of the rock) influence on the weathering process. The modelling of accelerated weathering was conducted in Chamber for Ageing Acceleration, where some weather circumstances were simulated (insolation, rain and frost). As the result of the weathering experiment it could be stated that the dominant mechanism of the sandstones deterioration was granular disintegration and weight loss as a consequence of sample destruction. The most important factor influencing rock deterioration is rock texture, especially the character of grain contacts. The effective porosity is a requisite of potential for the stone to take in and hold water, and hence of resistance to weathering. In case of silica-cemented sandstones, the deciding criterion influencing weathering resistance is pore structure. In case of sandstones with clay cement, the most important is mineral composition of the rock.