Micro-topographic and Geotechnical Investigations of sandstone Wall on Weathering Progress, Aachen City, Germany, case study

Abstract

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, e.g., to compute weathering rate, weathering intensity, and rock’s durability to weathering processes and to take a decision regarding restoration urgency. The current study aims to examine the variation/constancy of micro-topography and geotechnical properties’ limits of the sandstone constituting well-aged wall, at Aachen City, on weathering progress over short duration (7 years of investigation from 2007 to 2014). The micro-erosion meter and Equotip hardness tester are tools used for micro-topographic and rock’s surface hardness investigations on one hand, and the mercury intrusion porosimetry has been used for pore size distribution and salt susceptibility investigations on the other hand. These tools are accurate, numerical, comprehensive, easily applicable, and preferable particularly for ancient buildings where sampling is not recommended or prohibited. The wall side under consideration has been selected as its constructional blocks present a wide spectrum of weathering forms as well as rock’s surface micro-topography (over 7 years of investigation) through increasing the weathering forms’ dimensions and/or creation of new weathering forms. The net result of the current study indicated a noticeable variation in stone’s micro-topography on weathering progress particularly for stones’ surface with scaling, exfoliation, and a decrease in stone’s surface hardness. The critical pore size distribution that has increased rock’s susceptibility to weathering particularly by salts has been defined.