Degradation and Decay of Rocks: Linking Wetting–Drying and Slake Durability Tests for Climate-Sensitive Maintenance

Soft and weak rocks present challenges for construction activities in various environments. Their genetic origin, geological and tectonic evolution, and exposure to atmospheric conditions control their weathering and degradation over time. Therefore, a sound characterization of the associated rock parameters is essential. Numerous tests have been developed and standardized or defined in recommendations to assess various geomechanical, petrological, and mineralogical parameters. However, these tests are still subject to modification or extension to address project-specific issues. Additionally, standardized tests do not consider regional climatic conditions that may affect weathering, meaning they do not reflect the degradation behavior that is observed in the field. The present study investigates the slaking resistance and degradability of a range of soft rocks. The workflow of widely used tests is employed to evaluate their representativeness for different rock types in practical applications. Depending on their genetic origin and mineral composition, fabric alterations affect the rate and style of rock disintegration differently. Soft sedimentary rocks react already to static slaking, i.e., water immersion, whereas crystalline and grain-bound rocks slake under dynamic action while undergoing attrition in a rotating slake durability drum. Zones of structural weakness, such as foliation planes, are responsible for material removal in the latter; sedimentary rocks, on the other hand, are subject to surface particle separation (suspension) and suction due to the presence of clay minerals. This study presents an approach that combines the results of several routine tests to help identify and refine the slaking susceptibility of different rock types. A routine for inspecting and documenting the evaluated slaking characteristics for infrastructure maintenance is proposed, and the wider implications in light of climate change are discussed. Some limitations of the transferability of laboratory values to field sites still have to be evaluated and validated in the future.