Large-scale shear test of brash ice

A large-scale shear apparatus has been originally developed and built to test the mechanical properties of coarsegrained material. It was used to evaluate the shear behaviour of brash ice. The brash ice blocks were collected at Luleå harbour in two separate measuring campaigns in March 2020 and March 2021. The shear cylinder was loaded with brash ice in Luleå port in two different locations for the two test campaigns, and the displacementcontrolled shear tests were conducted. A vertical actuator was used to set a constant normal load and then a horizontal actuator was used to move the shear swing. In this setup, time, forces, and displacements were recorded at the forward and return stroke of the horizontal actuator. In total 6 shear cycles on two brash ice samples with axial stress of 4.8 kPa, 2 kPa and 1 kPa were performed. The test data was analysed to determine the relationship between shear stress and shear strain. The macro-porosity and confining axial force were found to be the most influential factors in determining the strength and deformation of the brash ice. Furthermore, an attempt has been made to estimate a few parameters of a material model known as the Continuous Surface Cap Model.publishedVersio

Brash Ice and Level Ice Growth, Effects of Snow

Brash ice occurs due to frequent navigation in ice-infested waters, typically along established navigation tracks regularly maintained by icebreakers and harbors. The accumulation and consolidation of brash ice between two ship passages are influenced by meteorological factors including the cumulative freezing air temperatures, and the mechanical processes such as ice-breaking due to ship passages. Brash ice's physical and thermodynamic properties also significantly influence the accumulation process. Brash ice formation and growth can occur rapidly, and the accumulations pose hazards to shipping operations. Vessels lacking ice-breaking capabilities often need assistance from icebreakers, resulting in heightened operational costs, greater fuel consumption, and increased greenhouse gas emissions. Navigation in icy waters relies on operational strategies that can be enhanced and guided by reliable forecast models. Accurate prediction of brash ice growth in Subarctic and Arctic regions is crucial for port and ship design. However, our understanding of brash ice development remains incomplete, and existing brash ice models can be improved and validated through the integration of full-scale data. Moreover, there has been limited research into the physical and mechanical properties of brash ice. Full-scale results are invaluable for both model-scale studies and developers seeking to estimate ship performance in brash ice conditions. This thesis presents the study of various parameters affecting brash ice formation and is validated by data from three full-scale brash ice channels and two harbors situated in the Bay of Bothnia, Luleå, Sweden. The primary objective was to assess the impact of snow on brash ice formation and growth. To begin with, laboratory-scale experiments were conducted to study the simultaneous growth of water and slush under identical meteorological conditions. Concurrently with the laboratory-scale experiments, the growth of brash ice in three full-scale channels and the growth of level ice adjacent to the ship channels were examined. Parameters under investigation included thickness profiles along the channel cross-section, macroporosity, distribution of brash ice piece sizes, and lateral movement of brash ice. Additionally, the study explored snow ice content, microstructure, microporosity, density, and uniaxial compressive strength. The laboratory scale experiments revealed that slush freezing occurred more rapidly than water freezing, primarily due to the porous nature of the slush, where freezing took place within the water-filled pores. Also, the freezing front of the slush remained insulated from direct contact with the warmer water from the slush layer underneath, whereas the freezing front of water was in direct contact with the water column. Based on the laboratory-scale experiments and full-scale observations, two key effects of snow on brash ice growth were identified: snow insulation between two ship passages and the transformation of snow into slush and then into snow ice after navigation. These effects were integrated into a brash ice growth model, and the model results were validated using full-scale data. The findings of the modelling supported by the measurement data, showed that in ship channels with low frequency of navigation and where snow remained on the brash ice for extended periods, snow insulation had a more substantial impact on brash ice growth compared to the snow-slush-snow ice transformation. Conversely, in frequently navigated channels where incoming snow was more often submerged, the snow-slush-snow ice transformation played a more prominent role in brash ice growth. It was also found that brash ice had the lowest snow ice content, while the level ice had the highest. In addition, the channel's initial macroporosity was estimated through the correlation between measured porosities and cumulative freezing air temperatures. This estimated initial porosity was integrated into the brash ice growth model along with the sideways motion of brash ice at each ship passage. It was found that in the less frequently navigated and narrower channels, the amount of brash ice expelled a teach vessel passage was significantly higher than in the wider and more frequently navigated channels. The piece sizes and piece distribution were investigated for two full-scale ship channels and two different harbors, revealing that the brash ice pieces were larger in ship channels compared to harbors. The piece size distributions could be well described by a three-parameter log normal probability density function

Brash Ice and Level Ice Growth, Effects of Snow

Brash ice occurs due to frequent navigation in ice-infested waters, typically along established navigation tracks regularly maintained by icebreakers and harbors. The accumulation and consolidation of brash ice between two ship passages are influenced by meteorological factors including the cumulative freezing air temperatures, and the mechanical processes such as ice-breaking due to ship passages. Brash ice's physical and thermodynamic properties also significantly influence the accumulation process. Brash ice formation and growth can occur rapidly, and the accumulations pose hazards to shipping operations. Vessels lacking ice-breaking capabilities often need assistance from icebreakers, resulting in heightened operational costs, greater fuel consumption, and increased greenhouse gas emissions. Navigation in icy waters relies on operational strategies that can be enhanced and guided by reliable forecast models. Accurate prediction of brash ice growth in Subarctic and Arctic regions is crucial for port and ship design. However, our understanding of brash ice development remains incomplete, and existing brash ice models can be improved and validated through the integration of full-scale data. Moreover, there has been limited research into the physical and mechanical properties of brash ice. Full-scale results are invaluable for both model-scale studies and developers seeking to estimate ship performance in brash ice conditions. This thesis presents the study of various parameters affecting brash ice formation and is validated by data from three full-scale brash ice channels and two harbors situated in the Bay of Bothnia, Luleå, Sweden. The primary objective was to assess the impact of snow on brash ice formation and growth. To begin with, laboratory-scale experiments were conducted to study the simultaneous growth of water and slush under identical meteorological conditions. Concurrently with the laboratory-scale experiments, the growth of brash ice in three full-scale channels and the growth of level ice adjacent to the ship channels were examined. Parameters under investigation included thickness profiles along the channel cross-section, macroporosity, distribution of brash ice piece sizes, and lateral movement of brash ice. Additionally, the study explored snow ice content, microstructure, microporosity, density, and uniaxial compressive strength. The laboratory scale experiments revealed that slush freezing occurred more rapidly than water freezing, primarily due to the porous nature of the slush, where freezing took place within the water-filled pores. Also, the freezing front of the slush remained insulated from direct contact with the warmer water from the slush layer underneath, whereas the freezing front of water was in direct contact with the water column. Based on the laboratory-scale experiments and full-scale observations, two key effects of snow on brash ice growth were identified: snow insulation between two ship passages and the transformation of snow into slush and then into snow ice after navigation. These effects were integrated into a brash ice growth model, and the model results were validated using full-scale data. The findings of the modelling supported by the measurement data, showed that in ship channels with low frequency of navigation and where snow remained on the brash ice for extended periods, snow insulation had a more substantial impact on brash ice growth compared to the snow-slush-snow ice transformation. Conversely, in frequently navigated channels where incoming snow was more often submerged, the snow-slush-snow ice transformation played a more prominent role in brash ice growth. It was also found that brash ice had the lowest snow ice content, while the level ice had the highest. In addition, the channel's initial macroporosity was estimated through the correlation between measured porosities and cumulative freezing air temperatures. This estimated initial porosity was integrated into the brash ice growth model along with the sideways motion of brash ice at each ship passage. It was found that in the less frequently navigated and narrower channels, the amount of brash ice expelled a teach vessel passage was significantly higher than in the wider and more frequently navigated channels. The piece sizes and piece distribution were investigated for two full-scale ship channels and two different harbors, revealing that the brash ice pieces were larger in ship channels compared to harbors. The piece size distributions could be well described by a three-parameter log normal probability density function

Field measurements on the behavior of brash ice

The behavior and properties of brash ice are important issues for the design of ice-going vessels. Heavy brash ice conditions may cause vessels to be dependent on ice-breaker assistance and time delays in the shipping schedule. Brash ice properties are not well studied and full-scale field data are missing in order to verify numerical models on brash ice and broken sea ice in general. The recent study describes new field equipment for testing brash ice and its functionality is tested on brash ice produced by the Swedish Ice-breaker Oden during ice management operations in the Barents Sea. The equipment consists of a big collector, connected to a crane, which is lowered below the brash ice cover. The brash ice mass above is pulled up by the crane and the force required for pulling is measured. A series of 18 field tests were performed and presented. Strengths and weaknesses of the method were evaluated. Ice blocks sizes were measured. The peak load during pull-up was often at least twice the weight of the lifted ice blocks when the blocks were interlocked. For free floating blocks, the peak load conformed to the weight of the blocks.publishedVersio

An Overview of Smart Materials and Technologies for Concrete Construction in Cold Weather

Cold weather conditions pose significant challenges to the performance and durability of concrete materials, construction processes, and structures. This paper aims to provide a comprehensive overview of the material-related challenges in cold weather concrete construction, including slow setting, reduced curing rate, and slower strength development, as well as frost damage, early freezing, and freeze–thaw actions. Various innovative materials and technologies may be implemented to address these challenges, such as optimizing the concrete mix proportions, chemical admixtures, supplementary cementitious materials, and advanced construction techniques. The paper also examines the impact of weather-related challenges for personnel, equipment, and machinery in cold environments and highlights the importance of effective planning, communication, and management strategies. Results indicate that the successful implementation of appropriate strategies can mitigate the challenges, reduce construction time, and enhance the performance, durability, and sustainability of concrete structures in cold and freezing temperatures. The paper emphasizes the importance of staying updated about the latest advancements and best practices in the field. Future trends include the development of smart and functional concrete materials, advanced manufacturing and construction techniques, integrated design, and optimization of tools, all with a strong focus on sustainability and resilience

Material and Environmental Aspects of Concrete Flooring in Cold Climate

Dehydration of concrete floor slabs is a critical step to ensure that the flooring material adheres properly and that there is no moisture-related damage to the floor after installation. Dehydration in a cold climate is often a slow process, which can have a big impact on the overall duration of the construction project, and corresponding measures are often taken to accelerate the drying process, especially in constructions exposed to a cold climate. One common method, typically used to accelerate dehydration in cold weather, is to introduce internal heating cables into the slab. This method reduces the dehydration time, but may not be the best solution from a sustainability perspective. This paper presents a concept study of concrete flooring in a cold climate from a cradle to practical completion perspective. The study focused on the environmental and material aspects of the dehydration of concrete floors in a cast-in-place house. This paper showed that concretes with high water-cement ratios, which are typically preferred due to their low CO2 emissions, may require measures for accelerated dehydration, which ultimately results in a higher environmental impact. The importance of environmental studies is also highlighted to fully understand the environmental aspects of construction

Physical and mechanical properties of ice from a refrozen ship channel ice in Bay of Bothnia

Winter navigation in the North Sea is expanding with respect to vessel size and traffic volume. Icebreakers create routes for ice-going vessels by breaking the level ice cover. Repeated vessel passages in the fairways and harbors initiate the formation of brash ice. The brash ice has the ability to refreeze quickly. In the current work, a field study was conducted on a refrozen brash ice ship channel located in Marjaniemi harbor in Bay of Bothnia. Aim of this study is to evaluate the structure and the strength of ice in the fully refrozen ship channel. Ship channel geometry, ice temperature and salinity were assessed in the field. The ice thickness was in average 45 cm covered by a snow layer with an average of 20 cm. The temperature profiles showed approximately -15ᴼC at the ice surface and close to 0ᴼC in the depths above 10 cm. Salinity varied from 0 to 1.5 ppt. Ice texture, density and compressive strength of refrozen brash ice were measured in the laboratory on 200 mm diameter cores. The behavior of refrozen brash ice with random ice texture was more ductile and stronger in uniaxial compression compared to the adjacent level ice.publishedVersio

Field measurements on the behavior of brash ice

The behavior and properties of brash ice are important issues for the design of ice-going vessels. Heavy brash ice conditions may cause vessels to be dependent on ice-breaker assistance and time delays in the shipping schedule. Brash ice properties are not well studied and full-scale field data are missing in order to verify numerical models on brash ice and broken sea ice in general. The recent study describes new field equipment for testing brash ice and its functionality is tested on brash ice produced by the Swedish Ice-breaker Oden during ice management operations in the Barents Sea. The equipment consists of a big collector, connected to a crane, which is lowered below the brash ice cover. The brash ice mass above is pulled up by the crane and the force required for pulling is measured. A series of 18 field tests were performed and presented. Strengths and weaknesses of the method were evaluated. Ice blocks sizes were measured. The peak load during pull-up was often at least twice the weight of the lifted ice blocks when the blocks were interlocked. For free floating blocks, the peak load conformed to the weight of the blocks

Possible Effects of Sea Ice on Concrete Used in Arctic Conditions

The Arctic region is receiving an increasing attention due to the diminishing area of the permanent ice and easing access to various natural resources including especially oil, gas and rare metals. The nearest future will require building a significant number of new harbors and other structures related to sea operations and exploration. Harsh weather conditions including especially extreme freezing temperatures, snowfall and ice formation impose demanding requirements, which must be taken into account while designing, building and maintaining those structures. Concrete is the main construction material used for harbor structures. Unfortunately, the usage of Portland cement, which is the main cementitious binder used for concrete, it involves hardening processes, which are controlled by the hydration reactions. The hydration needs water and temperatures above freezing point, which impose serious limitations in the arctic environment. Furthermore, later exposure to the arctic conditions and especially to ice may impair its long-term durability and thus the sustainability of built structures. The present work focuses on characterization of properties of sea ice forming in harbors located in the Arctic region and on identification of possible implications on concrete material during the construction phase but also in long-term exploitation

Formwork Engineering for Sustainable Concrete Construction

This study provides a comprehensive review of the engineering challenges of formwork in concrete construction. The paper investigates different formwork systems, their design based on form pressure, and the difficulties of form stripping. Alternative binders are gaining more and more interest by opening new opportunities for sustainable concrete materials and their impact on form pressure and concrete setting is also investigated in this paper. The discussion involves several engineering challenges such as sustainability, safety, and economy, while it also explores previous case studies, and discusses future trends in formwork design. The findings pinpoint that choosing an appropriate formwork system depends significantly on project-specific constraints and that the development of innovative materials and technologies presents significant benefits but also new challenges, including the need for training and regulation. Current trends in formwork design and use show promising possibilities for the integration of digital technologies and the development of sustainable and ‘smart’ formwork systems. Continued research within the field has the possibility to explore new formwork materials and technologies, which will contribute to the implementation of more effective and sustainable practices in concrete construction.Godkänd;2024;Nivå 0;2024-02-26 (signyg);Full text license: CC BY</p