This study introduces a fast 1D nuclear magnetic resonance (NMR) imaging method based on multi-slice imaging with a stepper motor to study sedimentation dynamics of clayey soils. Traditional NMR is limited by long acquisition times due to water’s T₁ relaxation time. Our approach combines multi-slice imaging with a stepper motor and frequency-based selection, reducing measurement time while maintaining sub-millimeter resolution, at the same time overcoming the limitations by the slow relaxation of water. This nondestructive method provides detailed insights into the sedimentation and consolidation of suspensions, including pore size distribution and density profiles within a single measurement. The technique is demonstrated with kaolinite clay suspensions, highlighting the technique’s ability to capture the dynamics of gravity-driven systems rapidly and accurately, even for fast-sedimenting soils such as kaolinite in the first hours of sedimentation. This advancement is valuable for geotechnical and environmental applications where understanding sedimentation is crucial.

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Salt crystallization represents one of the major causes for the degradation of building and ornamental stone. As such, it has attracted the attention of researchers, who over the years have progressively unraveled most mechanisms involved in salt damage. Despite this mechanistic understanding, many questions subsist about how to quantitatively predict damage or its progression, and in particular how to relate performance on site to that in laboratory tests.
In this context, a new RILEM TC 271‐ASC has been started with the objective of defining laboratory tests that deliver more reliable predictions of field behavior. One deliverable of this TC is to provide a theoretical insight into this question based on recent progress on the understanding of salt damage.
This paper presents a summary of this work, highlighting key aspects relating to crystallization pressure, chemo‐mechanics and mass transport. Implications are discussed in relation to the most used accelerated salt crystallization tests in an attempt to better define which field exposure conditions that these tests best represent and may be used for, or define effective test procedures representing specific field conditions. A simple conceptual model for the development of salt damage is introduced. During an initial “induction” phase, transport of ions and accumulation of salt in the porous materials occurs without causing detectable damage until a critical point, termed “damage onset” is reached. Beyond this point, during the “propagation phase”, the material degrades, typically losing strength and cohesiveness. The implications of these two phases are discussed in relation to the selection of appropriate salt weathering tests and conservation interventions.@en

The aim of this study is to investigate the effect of water migration from cracks into the bulk paste on autogenous self-healing. Nuclear magnetic resonance (NMR) technique was utilized to monitor water migration from cracks into the bulk paste during the process of autogenous self-healing. NMR results show that initially the water in the crack migrates into the bulk paste and the water content of the bulk paste increases significantly. However, after 5-h autogenous self-healing, the amount of non-chemically bound water in the bulk paste (adjacent to the crack surfaces) determined by NMR decreased instead. It indicates that some of the water coming from the crack was used for additional hydration of unhydrated cement particles in the bulk paste (during the process of autogenous self-healing). Before this study, in term of autogenous self-healing only the recoveries that related to the filling of cracks were concerned. The observation and quantification of densification of cement paste adjacent to the crack surfaces provides a new insight into autogenous self-healing.

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