• A benchmarking exercise involving 24 laboratories was organized to measure the permeability of the Grimsel granodiorite • The influence of pore fluid, sample size, pressure sensitivity and methods (steady-state, transient pulse, oscillation) are discussed • The average permeability measured with gas is larger than that measured with liquid
S U M M A R YUniaxial and triaxial compression experiments were performed on oolitic iron ores to investigate damage processes. Most of these experiments included four indirect measurements of damage evolution, that is, P-wave velocity and maximum amplitude received during pulse transmission experiments, elastic properties (apparent Young´s modulus and apparent Poisson´s ratio) and acoustic emission (AE) monitoring. The mechanical behaviour deduced from strain measurements is dilatant for some samples and non-dilatant for the other samples. However, variations in elastic properties indicate damage processes for all samples. AE source mechanism analysis shows two different microscopic damage processes: (1) for dilatant rock, the development of axial extensive microcracks as well as their interaction and coalescence lead to the formation of shear macroscopic discontinuities; (2) for non-dilatant oolitic iron ore, both compressive and shear micromechanisms take place and interact with macroscopic fractures. A particular consistency between the four types of measurements employed was observed.
• A benchmarking exercise involving 24 laboratories was organized to estimate the permeability of the Grimsel granodiorite • The microstructures of the Grimsel granodiorite were analyzed and quantified using BIB-SEM, micro-CT scanning, MICP and NMR techniques • Permeability predictions from different models using microstructure data as input parameters are in good agreement with measurements
Sodium sulfates are well known to be the most damaging salts in building materials and rocks. Unfortu- nately, the crystallization processes of sodium sulfates are not completely understood. In addition, the metastable heptahydrate has long been neglected in scientific works on salt damage until recently. In this study, we use tempera- ture monitoring and differential scanning calorimetry to detect and identify the crystallization of sodium sulfate hydrates (i.e., mirabilite and heptahydrate) upon cooling/ heating a bulk solution. The presence of impurities seems to play a major role in the crystallization sequence and can explain the crystallization of mirabilite and ice close to -10 °C. The crystallization of heptahydrate does not seem to be sensitive to the presence of impurities and does not always occur prior to the crystallization of mirabilite as commonly observed. The heptahydrate and mirabilite show different and characteristic thermal signatures that enable to distinguish each other. The shape, the intensity and the duration of the peak of temperature due to the crystalli- zation depict these differences. Therefore, the thermal signatures can be used in further experimental studies to estimate the role of the different sodium sulfate hydrates involved in the salt weathering of rocks
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