Frost salt scaling of concrete is related to cyclic freezing and melting of a few millimeter thick deicer solution on the surface of the concrete. It is almost absent when pure water is freezing and reaches a maximum at a so-called pessimum concentration that for NaCl is around 3%. Different mechanisms have been suggested to explain this pessimum and frost salt scaling in general, ranging from the transport of moisture and growth of ice within the pore space of concrete (“cryogenic suction”) to crack formation in the saline ice layer followed by spalling off the surface (“glue-spall”). Though in these theories the saline ice layer, that forms in concrete frost salt scaling experiments, plays a major role, so far little is known about its properties. We present a characterisation and an analysis of the microstructure of this saline ice layer by means of 3D X-ray microtomography. We found that the morphology of the saline ice is very similar to young, columnar sea ice, with lamellae of ice and brine oriented in the direction of freezing. On the basis of the microscopic 3D image data, we formulated percolation-based models of macroscopic properties (e.g., strength, thermal expansion coefficient, porosity metrics) relevant for different proposed frost salt scaling mechanisms. Model results and observations suggest that the ice growth velocity, direction and confinement, have a major impact on the pore structure of saline ice, thereby governing both mechanical and transport properties. These properties in turn are expected to affect proposed frost salt scaling mechanisms of concrete. The microstructure length scales in the ice-brine composite (lamellar spacing, pore width) are comparable to those for concrete (air void spacing and size), suggesting complex poro-mechanical interaction at the interface of concrete and saline ice. The results highlight the importance of studying saline ice properties to improve predictions of frost salt scaling processes.

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The process of ice melting during abrasive interactions with concrete is essential in a variety of contact phenomena. In this paper, we refer to abrasive tests for different samples of concrete with roughness in the range of 9–35 μm. The experimental conditions were: 1 MPa ice pressure, ambient temperature −10 °C, average sliding velocity 0–0.16 m/s. Using the experimental logs, we balance the heat transfer in the ice-concrete contact zone to compute the amount of molten ice. The average melting of ice varies from 3 to 29% of total ice consumption. The highest melting rate of ice corresponded to the lowest ice consumption and lower average abrasion of concrete. The theoretical calculations are validated against benchmarked commercial software with an in-house melting model.@en

We simulate the glue-spall stress due to mechanical interactions between a frozen saline solution (brine-ice composite) and a non-air entrained concrete surface including the impact of the micro-structure of the frozen solution. The presence of brine channels at the ice/concrete interface was found to be a prerequisite to induce stress during freezing and hence for scaling to occur. Pure ice does not result in scaling as it does not have brine channels. Furthermore, the size of the brine channels and their distribution was found determinant for the magnitude of the glue-spall stress in the concrete and the experimentally observed pessimum effect of a medium salt concentration was explained based on the change of the microstructure of the brine-ice composite at different salt concentrations and temperatures. The predicted results are in good agreement with the experimental observations and the few numerical demonstrations related to frost salt scaling in the literature.

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Topography studies of concrete-ice abrasion were made to proceed in our understanding of the mechanisms of concrete wear by ice on Arctic offshore structures. The effects on various initial surfaces of a B75 normal-weight concrete (smooth, rough, sawn) and on the sawn surface of a LB60 lightweight concrete were studied during concrete-ice abrasion experiments. The degradation of a concrete surface appears mainly as valley formation resulting from air voids opening, or aggregate protrusion and cutting of peaks. The various initial roughness conditions were found to lead to an evolution with both increasing (at both meso- and microscale) and converging roughness. Protrusions from both lightweight and normal-weight aggregates were observed on sawn surfaces. Greater abrasion is seen on lightweight concrete and its initial roughness was much affected by the porous aggregate.@en

Concrete structures in the Arctic offshore are often exposed to drifting ice causing abrasion of concrete surfaces. This paper presents the results of a laboratory study of concrete-ice abrasion. The sawn concrete surfaces (two high-performance concrete mixes and one light weight mix of concrete) were exposed to sliding fresh-water ice under 1 MPa pressure for 3 km of sliding distance. The effect of concrete compressive strength, ice consumption, and the coefficient of friction on abrasion was studied simultaneously. The results show a low abrasion of concrete, the maximum abrasion depth (0.35 mm) after 3 km of sliding test was found for the concrete samples with the lowest compressive strength. All tests showed a severe-to-mild wear transition, with the maximum wear rate in the first sliding kilometre. The coefficient of friction was high when ice consumption was high due to ice spallation and pulverization, whereas the coefficient of friction was not directly correlated to the wear. The wear or consumption of the ice (abrasive) was in the order of 30,000–100,000 times that of concrete despite of its strength and stiffness 1–10 times lower than that of concrete.

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