Preface

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Frost deterioration of concrete is an important durability issue for structures exposed to high degree of saturation, low temperatures and de-icers. The material can then be severely damaged with internal cracking and/or scaling of the surface, which can lead to e.g. reduced protection of the reinforcement and loss of load bearing capacity. Experiments with liquid uptake in concrete using different temperature cycles was made to study cryosuction. The material used was concrete with different air content and different replacement levels of ground granulated blast-furnace slag (GGBS). The concrete samples were preconditioned by capillary suction. Three temperature conditions were used: constant temperatures of +20 °C and -20 °C, and temperature that cycled between -20 °C and +20 °C. As liquid medium, deionized water and a 3% NaCl salt solution were used. Air entrainment generally increased the liquid uptake. The amount of GGBS and the NaCl concentration in the liquid did not have any significant impact on the liquid uptake in these experiments.
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Department of Materials Science and Applied Mathematics

Cryosuction Experiments on Concrete Containing Ground Granulated Blast-Furnace Slag: Influence of Temperature, Air Entrainment And Salt

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Post-cast application of hydrophobic agents onto hardened concrete is successful at reducing external ion diffusion into cement paste, this work examines pre-cast application of hydrophobic admixtures in fresh concrete. Concretes, with water to cement ratios (w/c) 0.45 and 0.50 (CEM I; low C3A), were mixed. Adding alkyltrialkoxysilane or triacylglycerol admixtures ranging from 1 to 3 wt%cem in these concretes were evaluated. Increasing the dosage of hydrophobic admixtures decreased the compressive strength. The usage of these admixtures did not hinder the further development of the microstructure as all concretes gained strength after one year, but not in the same percentage increase as the reference concrete. Chloride ion diffusion, after exposure to 3 wt% NaCl solution at 20 °C for 91 days, in concretes with 1 wt%cem admixture showed slight reductions in diffusion rate (8-17%) compared to the reference. At 3 wt%cem, triacylglycerol admixtures showed better hindering effects of inward chloride diffusion, this was especially evident in w/c = 0.45. Equivalent addition of alkyltrialkoxysilane-based admixtures increased the diffusion of chloride ions transferred into the cement matrix.
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Dept. of Civil & Architectural Engineering

PhD, Department Manager, Havsfiskelaboratoriet / SLU-Aqua

Chloride Ion Diffusion Resistance of Bulk Hydrophobic Concrete: Comparison of w/c and Dosages

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This paper describes the structural effects of ASR expansion in reinforced structures. It proposes models and procedures for calculating the strains in the concrete caused by the reinforcement, the load effects in statically indeterminate structures and the cross-sectional capacities. Three models are described to include variations of the ASR expansion in a section. Model 1 for constant or linearly varying ASR expansion, Model 2 for an expansion variation in different parts of a cross-section and Model 3 for a particular case of different expansion in subsections of the cross-section. The models are exemplified by calculations based on input data from one relevant bridge, the 70 years old Elgeseter bridge in Trondheim, Norway. This is done to illustrate various aspects of the calculation methods and show the structural consequences of the ASR expansion. The results correlate with the bridge’s observed structural behavior and assumed expansion. This paper also illustrates the importance of coordinating inspection, material testing and structural strength analysis to obtain reliable assessment.
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M.Sc. Department of structural engineering

Professor, Department of structural engineering

Load Effects of ASR-induced Expansion in Reinforced Concrete and Their Consequences for Structural Assessment

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The effective width is a relevant parameter for the design of bridge overhang slabs under concentrated loads. Experimental tests have been used to assess expressions for its calculation. However, the load capacity increases with the width until a transition area is reached. Test specimens may have lacked enough width to reach full shear capacity, affecting thus the evaluation of the results. On the other hand, within the transition area, a threshold value has been hypothesized to match the effective width. This paper aims to provide recommendations for minimal widths that guarantee the full capacity of overhang slabs and to assess the calculation of the effective width by means of the threshold value and other formulations. The effect of the edge beam is also considered. A campaign of validated non-linear FE-simulations based on experiments on range of width-span ratios was performed. The results suggest using a width-span ratio of at least 4.0 for slabs without an edge beam and 5.3 for slabs with an edge beam for the experimental practice. The efficiency of the formulation for the effective widths is diffuse and the use of threshold value leads to unsafe predictions. Instead, linear-elastic FE-analyses are recommended for the design practice.
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Dept. of Civil & Architectural Engineering, Division of Structural Engineering and Bridges

Assessment of Effective and Minimal Slab Widths for Evaluating the Shear Capacity of RC Overhang Slabs

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There is a great need for an easy-to-use tool to simulate drying of concrete floors. In order to model practical situations, the tool should take into account changing conditions, especially wetting at worksite, but also temperature. For this purpose, a simulation program was developed for drying time estimations for concrete floors, which was published in 2021 and is named as the “by2020 Concrete drying time estimate”. This study presents the results of the laboratory test series conducted to calibrate the drying time estimations of the by2020 software. As all possible scenarios for practical situations were not possible to study in the test series, results from the literature were partly used for calibration and validation of the tool. A methodology for test series for calibration of the drying time estimation model is proposed based on this study. It was found that a model suitable for practical applications can be implemented based on relative humidity measurements only. However, the tests series of relative humidity measurements should take into account the influence of various factors such as wetting period and different temperature conditions.
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Requirements for Test Series for Relative Humidity Measurements to Calibrate Drying Time Simulation Model

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This review paper highlights the most fundamental state of knowledge regarding the fatigue of concrete that is available through the literature over the last decades and reveals the areas that are needed for further investigation. The loading factors influencing the fatigue performance and the fatigue life estimation of concrete structures are taken into consideration. This review explores the impact of eight loading parameters on the fatigue life of concrete structures, and we aimed to be succinct in our investigation. Besides, we present a review on the deterministic and probabilistic approaches for fatigue life prediction. For example, in more recent studies, the utilization of machine learning techniques has been shown to outperform the traditional methods. The review gives adequate insight into the approach of some of the main current design codes for fatigue life prediction of concrete.
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Ph.D. Candidate, Department of Structural Engineering

Associate Professor, Department of Structural Engineering

Professor, Department of Structural Engineering

A Review on Fatigue Performance of Concrete Structures Part I: Loading Parameters, Current Prediction Models and Design Approaches

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Fatigue is a critical issue for concrete structures subjected to repetitive and varying loads, particularly in infrastructure and transportation systems. This review paper presents a comprehensive overview of the current state of knowledge on concrete fatigue and identifies areas for further research. Material and size factors that influence fatigue performance and life estimation of concrete such as concrete composition, internal moisture content and reinforcement are explored, along with environmental conditions such as presence of external moisture and seawater exposure. The paper also acknowledges the challenges associated with predicting concrete fatigue life accurately due to the heterogeneous nature of concrete and its complex behavior under cyclic loading.
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A Review on Fatigue Performance of Concrete Structures Part II, Material Parameters and Environmental Factors

AHEAD OF PRINT

Volume 69 (2023): Issue 2 (December 2023)

Volume 68 (2023): Issue 1 (July 2023)

Volume 67 (2022): Issue 2 (December 2022)

Volume 66 (2022): Issue 1 (July 2022)

Volume 65 (2021): Issue 2 (December 2021)

Volume 64 (2021): Issue 1 (June 2021)

Volume 63 (2020): Issue 2 (December 2020)

Volume 62 (2020): Issue 1 (June 2020)

Volume 61 (2019): Issue 2 (December 2019)

Volume 60 (2019): Issue 1 (June 2019)

Volume 59 (2018): Issue 1 (December 2018)

Volume 58 (2018): Issue 1 (June 2018)

Nordic Concrete Research

 The aim is to publish reviewed papers on research, recent experiences, and education within the broad concrete field. The scope covers all aspects of concrete and other cementitious materials, e.g., materials, design, construction, assessment, maintenance, repair, strengthening, dismantling, and recycling. The scope is limited to papers that have a Nordic connection, e.g., through the environment conducting the investigation, affiliation of any of the authors, or if the subject of the paper is devoted to any specific Nordic circumstances such as geographical, geological, or organizational ones.The Nordic Concrete Federation (NCF) which is publishing the bi-annually publications Nordic Concrete Research (NCF), is a collaboration organization of the concrete associations in the five Nordic countries, Denmark, Finland, Iceland, Norway and Sweden. Read more about NCF on www.nordicconcrete.net.  "Nordic Concrete Research” has no article processing chargers (APCs) nor article submission charges.  Archiving  Sciendo archives the contents of this journal in Portico - digital long-term preservation service of scholarly books, journals and collections.  Plagiarism Policy  The editorial board is participating in a growing community of Similarity Check System's users in order to ensure that the content published is original and trustworthy. Similarity Check is a medium that allows for comprehensive manuscripts screening, aimed to eliminate plagiarism and provide a high standard and quality peer-review process. 