Weathering Progress and Its Mapping Using Non-Destructive Tools and GIS, Eleven Years of Investigation, Aachen City Sandstone Walls, Germany, Case Study

Rock's surface micro-topography and geotechnical properties' limits are almost altered, on weathering progress, to a new form(s) and limits respectively. The quantification of weathering damage for a given rock is of value to take a decision regarding conservation urgency. The current study aims to examine the variation/constancy of micro-topography, geotechnical properties’ limits and the damage category distribution and its variation for the sandstone constituting the ancient Aachen City wall, on weathering progress over eleven years of investigation (2007 and 2018). The Micro-erosion meter (MEM) and Equitop Hardness Tester (EHT) are tools used for micro-topographic and rock's surface hardness investigations. Arc GIS (10.1) had been used to find out the distribution and mean damage category at four representative parts of this wall on 2007 and 2018. These tools are accurate, numerical, easily applicable and preferable particularly for ancient buildings where sampling is not recommended or prohibited. The wall side under investigation had been selected as its constructional blocks present a wide spectrum of weathering forms and damage categories. The net result of the current study indicated a noticeable variation in stone's microtopography and reduction of rock's surface hardness over the period of investigation. The rock's mean damage category had been increased from slight to moderate over the eleven years of investigation as mapped and mathematically processed using GIS (10.1).

Keywords: Field investigations, MEM, EHT, GIS mapping for rock's damage categories.