Nordic Concrete Research最新文献

A Review on Fatigue Performance of Concrete Structures Part I: Loading Parameters, Current Prediction Models and Design Approaches 混凝土结构疲劳性能研究综述:荷载参数、现有预测模型和设计方法

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Nordic Concrete Research Pub Date : 2023-07-01 DOI: 10.2478/ncr-2023-0002

Mohammad Afaghi, B. Anja, Jan Arve Øverli

引用次数: 0

Cryosuction Experiments on Concrete Containing Ground Granulated Blast-Furnace Slag: Influence of Temperature, Air Entrainment And Salt 含磨粒高炉渣混凝土的低温吸力试验:温度、夹带空气和盐的影响

Nordic Concrete Research Pub Date : 2023-07-01 DOI: 10.2478/ncr-2022-0008

David Wahlbom, Katja Fridh

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A Review on Fatigue Performance of Concrete Structures Part II, Material Parameters and Environmental Factors 混凝土结构疲劳性能研究进展第二部分:材料参数与环境因素

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Nordic Concrete Research Pub Date : 2023-07-01 DOI: 10.2478/ncr-2023-0005

Mohammad Afaghi, A. Klausen, J. Øverli

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Assessment of Effective and Minimal Slab Widths for Evaluating the Shear Capacity of RC Overhang Slabs 钢筋混凝土悬挑板抗剪承载力的有效和最小板宽评定

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Nordic Concrete Research Pub Date : 2023-07-01 DOI: 10.2478/ncr-2023-0003

Dr. José Javier Veganzones Muñoz, C. Pacoste, R. Karoumi

{"title":"Assessment of Effective and Minimal Slab Widths for Evaluating the Shear Capacity of RC Overhang Slabs","authors":"Dr. José Javier Veganzones Muñoz, C. Pacoste, R. Karoumi","doi":"10.2478/ncr-2023-0003","DOIUrl":"https://doi.org/10.2478/ncr-2023-0003","url":null,"abstract":"Abstract 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.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78555080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

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Requirements for Test Series for Relative Humidity Measurements to Calibrate Drying Time Simulation Model 校准干燥时间模拟模型的相对湿度测量试验系列要求

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Nordic Concrete Research Pub Date : 2023-07-01 DOI: 10.2478/ncr-2023-0007

Pauli Sekki, Sami Niemi, T. Karvinen

{"title":"Requirements for Test Series for Relative Humidity Measurements to Calibrate Drying Time Simulation Model","authors":"Pauli Sekki, Sami Niemi, T. Karvinen","doi":"10.2478/ncr-2023-0007","DOIUrl":"https://doi.org/10.2478/ncr-2023-0007","url":null,"abstract":"Abstract 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.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78205201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Chloride Ion Diffusion Resistance of Bulk Hydrophobic Concrete: Comparison of w/c and Dosages 大块疏水混凝土的氯离子扩散阻力:w/c和用量的比较

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Nordic Concrete Research Pub Date : 2023-07-01 DOI: 10.2478/ncr-2022-0020

P. Rogers, J. Silfwerbrand, Anders Selander, J. Trägårdh, P. Utgenannt

{"title":"Chloride Ion Diffusion Resistance of Bulk Hydrophobic Concrete: Comparison of w/c and Dosages","authors":"P. Rogers, J. Silfwerbrand, Anders Selander, J. Trägårdh, P. Utgenannt","doi":"10.2478/ncr-2022-0020","DOIUrl":"https://doi.org/10.2478/ncr-2022-0020","url":null,"abstract":"Abstract 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.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76992749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Load Effects of ASR-induced Expansion in Reinforced Concrete and Their Consequences for Structural Assessment 钢筋混凝土asr诱发膨胀的荷载效应及其对结构评估的影响

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Nordic Concrete Research Pub Date : 2023-07-01 DOI: 10.2478/ncr-2023-0001

Kathrine Mürer Stemland, H. Johansen, T. Kanstad

引用次数: 0

Failure Mechanisms of Fibre Reinforced Shotcrete: Numerical Simulations Considering Local Variations in Thickness and Bond Strength 纤维喷射混凝土破坏机制:考虑局部厚度和粘结强度变化的数值模拟

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Nordic Concrete Research Pub Date : 2022-12-01 DOI: 10.2478/ncr-2022-0016

A. Sjölander, A. Ansell

{"title":"Failure Mechanisms of Fibre Reinforced Shotcrete: Numerical Simulations Considering Local Variations in Thickness and Bond Strength","authors":"A. Sjölander, A. Ansell","doi":"10.2478/ncr-2022-0016","DOIUrl":"https://doi.org/10.2478/ncr-2022-0016","url":null,"abstract":"Abstract Fibre-reinforced shotcrete is the most common support method for hard rock tunnels in the Nordic countries. The design of shotcrete is often based on empirical methods or simplified analytical equations, which neglect variations in mechanical properties and shotcrete thickness. Data collected from the field shows that significant variations in shotcrete thickness and bond strength should be expected during tunnel construction. However, how this affects the structural behaviour and capacity of the shotcrete lining is unknown. Moreover, the design philosophy for shotcrete assumes that the primary failure modes of shotcrete, i.e. bond and flexural failure, can be treated separately. This was derived based on observations of experiments in a laboratory environment. Therefore, the focus of a finalized doctoral project was to develop a numerical framework to simulate the structural behaviour of fibre-reinforced shotcrete in interaction with hard rock and rock bolts. The effect of variations in shotcrete thickness and bond strength was studied through numerical simulations to increase the understanding of its effect on the failure load of the lining. The results indicate that the most important parameter is the mean value of the shotcrete thickness and bond strength around a narrow perimeter of the block.’","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76387571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of Set Accelerator on Capillary Suction and Porosity of Concrete – Cast Samples with Constant Water/Binder Ratio 固化剂对恒水胶比混凝土试样毛细吸力和孔隙率的影响

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Nordic Concrete Research Pub Date : 2022-12-01 DOI: 10.2478/ncr-2022-0011

Nicholas Trussell, Rolands Cepurītis, S. Jacobsen

{"title":"Effect of Set Accelerator on Capillary Suction and Porosity of Concrete – Cast Samples with Constant Water/Binder Ratio","authors":"Nicholas Trussell, Rolands Cepurītis, S. Jacobsen","doi":"10.2478/ncr-2022-0011","DOIUrl":"https://doi.org/10.2478/ncr-2022-0011","url":null,"abstract":"Abstract Alkali-free set accelerators are added at the nozzle to ensure rapid set of wet sprayed concrete. The accelerator affects the strength development, porosity and transport properties, and hence the durability, of the sprayed concrete. We developed a method to cast samples with varying set accelerator doses to measure the effect of the accelerator on porosity, but with a constant effective water/binder ratio of 0.45 for each accelerator dose. Six cylinders of concrete were cast with set accelerator doses of 0, 2, 4, 6, 8 and 10 % of effective binder mass. High workability was achieved to enable mixing before rapid stiffening occurred, though this high workability led to some aggregate settlement in the cylinders. Porosity was measured by capillary suction on dried specimens of hardened concrete and subsequent pressure saturation of macro pores (PF test). The samples cast with higher doses of set accelerator had higher suction porosities and higher rates of capillary suction. Using a modified Powers equation gave very low calculated degree of hydration values for concrete with set accelerator, indicating that the equation is not applicable for concrete with set accelerators, due to the higher suction porosity in accelerated matrices, caused by different hydration products.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82289377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

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Evaluation of Crushed Fine Materials 粉碎细料的评价

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Nordic Concrete Research Pub Date : 2022-12-01 DOI: 10.2478/ncr-2022-0015

Annika Gram, B. Lagerblad

引用次数: 0