Abstract As natural resources of sand and fine material used in the concrete industry are becoming more scarce, crushed materials are being used to a greater extent. Shape and texture of machine crushed materials differ from aggregates naturally ground, layered and sorted under the course of millions of years. It is assumed that crushed aggregates are more angular and of less smooth texture than natural aggregates, which will affect the flow behaviour of a suspension containing crushed material. In the mix design process of cementitous suspensions, an adequate rheology of the micro mortar (all constituents in the concrete being able to pass a 0.125 mm sieve, including the cement) is crucial. In this paper, the shape of fine particles is linked to the micro mortar plastic viscosity of the filler suspension including cement. The plastic viscosity here serves as an important quality assessment of the filler, since the micro mortar workability features are vital for the final mix design quality of the concrete workability.
{"title":"Evaluation of Crushed Fine Materials","authors":"Annika Gram, B. Lagerblad","doi":"10.2478/ncr-2022-0015","DOIUrl":"https://doi.org/10.2478/ncr-2022-0015","url":null,"abstract":"Abstract As natural resources of sand and fine material used in the concrete industry are becoming more scarce, crushed materials are being used to a greater extent. Shape and texture of machine crushed materials differ from aggregates naturally ground, layered and sorted under the course of millions of years. It is assumed that crushed aggregates are more angular and of less smooth texture than natural aggregates, which will affect the flow behaviour of a suspension containing crushed material. In the mix design process of cementitous suspensions, an adequate rheology of the micro mortar (all constituents in the concrete being able to pass a 0.125 mm sieve, including the cement) is crucial. In this paper, the shape of fine particles is linked to the micro mortar plastic viscosity of the filler suspension including cement. The plastic viscosity here serves as an important quality assessment of the filler, since the micro mortar workability features are vital for the final mix design quality of the concrete workability.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"63 10","pages":"65 - 77"},"PeriodicalIF":1.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72613230","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}
Magdalena Rajczakowska, M. Szeląg, K. Habermehl-Cwirzen, H. Hedlund, A. Ćwirzeń
Abstract This manuscript presents preliminary results on the cement paste potential, with and without carbon nanomaterials, to heal high-temperature cracks. Cement paste beams were subjected to thermal loading of 200°C and 400°C after 28 days of water curing. High temperature caused the formation of microcrack networks on the specimen’s surface. Self-healing was achieved by exposing the cracked samples to cyclic water immersion. The efficiency of the process was evaluated based on the crack closure and mechanical properties recovery after 24 days. The results indicated a distinct dependence of the healing on the loading temperature. Carbon nanotubes had a positive effect on self-repair efficiency.
{"title":"Is Cement Paste Modified with Carbon Nanomaterials Capable of Self-Repair after a Fire?","authors":"Magdalena Rajczakowska, M. Szeląg, K. Habermehl-Cwirzen, H. Hedlund, A. Ćwirzeń","doi":"10.2478/ncr-2022-0017","DOIUrl":"https://doi.org/10.2478/ncr-2022-0017","url":null,"abstract":"Abstract This manuscript presents preliminary results on the cement paste potential, with and without carbon nanomaterials, to heal high-temperature cracks. Cement paste beams were subjected to thermal loading of 200°C and 400°C after 28 days of water curing. High temperature caused the formation of microcrack networks on the specimen’s surface. Self-healing was achieved by exposing the cracked samples to cyclic water immersion. The efficiency of the process was evaluated based on the crack closure and mechanical properties recovery after 24 days. The results indicated a distinct dependence of the healing on the loading temperature. Carbon nanotubes had a positive effect on self-repair efficiency.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"128 1","pages":"79 - 97"},"PeriodicalIF":1.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78035287","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}
Abstract The Alkali-Silica Reaction (ASR) is a deleterious concrete chemical reaction that has been studied a lot since its discovery in 1940. The reaction produces a highly hygroscopic silica gel that swells into the pores of concrete, resulting in the critical decrease of the mechanical performances of the affected structures. Some methods have been investigated to limit expansion under a certain limit, among them lithium mitigation. However, the mechanisms are not really understood yet and determining the right amount of lithium is still arduous. An attempt for a method in coherence with experience is presented in this study, using the chemo-mechanical model of Larive and curve-fitting. The results provide accuracy to experimental measurements from several protocols, and call for further research.
{"title":"Empirical Modelling of Lithium Mitigation for Alkali-Silica Reactivity","authors":"Mark Vacher, S. Jacobsen","doi":"10.2478/ncr-2022-0003","DOIUrl":"https://doi.org/10.2478/ncr-2022-0003","url":null,"abstract":"Abstract The Alkali-Silica Reaction (ASR) is a deleterious concrete chemical reaction that has been studied a lot since its discovery in 1940. The reaction produces a highly hygroscopic silica gel that swells into the pores of concrete, resulting in the critical decrease of the mechanical performances of the affected structures. Some methods have been investigated to limit expansion under a certain limit, among them lithium mitigation. However, the mechanisms are not really understood yet and determining the right amount of lithium is still arduous. An attempt for a method in coherence with experience is presented in this study, using the chemo-mechanical model of Larive and curve-fitting. The results provide accuracy to experimental measurements from several protocols, and call for further research.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"1 1","pages":"1 - 14"},"PeriodicalIF":1.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84603649","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}
Abstract This paper describes sprayed concrete experiments varying the set accelerator dose. Literature on the hydration of cement with modern alkali-free set accelerators is reviewed and two full scale wet spraying experiments have been conducted, varying the dose of set accelerator in each. The effects on the properties of the hardening and hardened sprayed concrete were investigated by field and laboratory testing. Increasing the set accelerator dose was found to increase the rate of early age strength development but reduce density, long term strength and increase suction porosity of hardened sprayed concrete.
{"title":"Effect of Set Accelerator on Properties of Wet Sprayed Concrete","authors":"Nicholas Trussell, Rolands Cepurītis, S. Jacobsen","doi":"10.2478/ncr-2022-0005","DOIUrl":"https://doi.org/10.2478/ncr-2022-0005","url":null,"abstract":"Abstract This paper describes sprayed concrete experiments varying the set accelerator dose. Literature on the hydration of cement with modern alkali-free set accelerators is reviewed and two full scale wet spraying experiments have been conducted, varying the dose of set accelerator in each. The effects on the properties of the hardening and hardened sprayed concrete were investigated by field and laboratory testing. Increasing the set accelerator dose was found to increase the rate of early age strength development but reduce density, long term strength and increase suction porosity of hardened sprayed concrete.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"32 1","pages":"19 - 39"},"PeriodicalIF":1.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85586197","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}
Abstract This study investigates nonlinear modeling and verification of a reinforced concrete element using the fiber section method. At first, the theory related to the fiber section approach and hysteresis models used for cyclic analysis is given. Then, a reinforced concrete column tested previously in the literature is modeled and simulation results are compared with the test results. An acceptable approximation is made utilizing only a few input parameters: Uniaxial stress-strain curves of the materials, location and length of the plastic hinge, and geometry of the model. Moreover, the axial force-moments interaction curve from Eurocode is compared with the one obtained from the nonlinear model. It is shown that by conducting nonlinear analysis a larger capacity of the element is considered which results in a more realistic and economic design.
{"title":"Nonlinear Cyclic Analysis of Reinforced Concrete Columns Using Fiber Section Approach","authors":"A. Vatanshenas","doi":"10.2478/ncr-2022-0002","DOIUrl":"https://doi.org/10.2478/ncr-2022-0002","url":null,"abstract":"Abstract This study investigates nonlinear modeling and verification of a reinforced concrete element using the fiber section method. At first, the theory related to the fiber section approach and hysteresis models used for cyclic analysis is given. Then, a reinforced concrete column tested previously in the literature is modeled and simulation results are compared with the test results. An acceptable approximation is made utilizing only a few input parameters: Uniaxial stress-strain curves of the materials, location and length of the plastic hinge, and geometry of the model. Moreover, the axial force-moments interaction curve from Eurocode is compared with the one obtained from the nonlinear model. It is shown that by conducting nonlinear analysis a larger capacity of the element is considered which results in a more realistic and economic design.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"49 1","pages":"55 - 71"},"PeriodicalIF":1.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82634849","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}
Marianne Tange Hasholt, Katja Frid, F. Spörel, J. Lahdensivu, Elisabeth Helsing, Matthias Müller, Abdul Faheem, Sara Al Haj Sleiman, S. Jacobsen
Abstract A one-day Nordic Concrete Research workshop on “Accelerated freeze-thaw testing of concrete” attracted approx. 30 participants. The workshop included presentations on various aspects, such as observed frost damage in the field and the importance of the temperature curve during testing as well as other interactions with the surroundings of the concrete. The workshop also included examples of recent research, which can improve our knowledge about the frost damage mechanism and therefore provide input to improving the standardised test methods. The present paper is a summary of the nine presentations and the discussion arising from the presentations.
{"title":"Nordic Concrete Research workshop: “Accelerated freeze-thaw testing of concrete”, Lyngby, 20th April 2022","authors":"Marianne Tange Hasholt, Katja Frid, F. Spörel, J. Lahdensivu, Elisabeth Helsing, Matthias Müller, Abdul Faheem, Sara Al Haj Sleiman, S. Jacobsen","doi":"10.2478/ncr-2022-0007","DOIUrl":"https://doi.org/10.2478/ncr-2022-0007","url":null,"abstract":"Abstract A one-day Nordic Concrete Research workshop on “Accelerated freeze-thaw testing of concrete” attracted approx. 30 participants. The workshop included presentations on various aspects, such as observed frost damage in the field and the importance of the temperature curve during testing as well as other interactions with the surroundings of the concrete. The workshop also included examples of recent research, which can improve our knowledge about the frost damage mechanism and therefore provide input to improving the standardised test methods. The present paper is a summary of the nine presentations and the discussion arising from the presentations.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"66 1","pages":"113 - 133"},"PeriodicalIF":1.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84816094","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}
José Hernández Vargas, H. Westerlind, J. Silfwerbrand
Abstract Functionally graded materials (FGMs) describe composite materials with a gradual change in properties along one or several axes. A major advantage with this approach is the avoidance of discontinuities between different layers of material. 3D Printing offers the possibility to control the material composition and spatial placement along the printing process to create structures with graded properties. However, there are very few examples of the application of this approach to 3D concrete printing (3DCP). This paper presents a review of the current approaches of and methods to grade the material properties of a 3DCP structure, as well as a review of similar methods used in other 3D printing processes. Finally, the potential applicability of these principles into concrete are presented and discussed.
{"title":"Grading Material Properties in 3D Printed Concrete Structures","authors":"José Hernández Vargas, H. Westerlind, J. Silfwerbrand","doi":"10.2478/ncr-2022-0004","DOIUrl":"https://doi.org/10.2478/ncr-2022-0004","url":null,"abstract":"Abstract Functionally graded materials (FGMs) describe composite materials with a gradual change in properties along one or several axes. A major advantage with this approach is the avoidance of discontinuities between different layers of material. 3D Printing offers the possibility to control the material composition and spatial placement along the printing process to create structures with graded properties. However, there are very few examples of the application of this approach to 3D concrete printing (3DCP). This paper presents a review of the current approaches of and methods to grade the material properties of a 3DCP structure, as well as a review of similar methods used in other 3D printing processes. Finally, the potential applicability of these principles into concrete are presented and discussed.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"13 3 1","pages":"73 - 89"},"PeriodicalIF":1.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83148316","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}
Abstract Concrete cracks in structures such as water tanks and nuclear power stations cause anxiety to owners, contractors and engineers. These cracks may significantly increase the structure’s permeability and thus increase leakage, reduce durability, and eventually lead to loss of structural functionality. Therefore it is important to minimize their occurrence and size. To identify effective ways of minimizing cracking in young concrete segments, a parametric study was conducted using the finite element method (FEM). Parameters considered include casting sequence, joint position, wall height, and cooling. The study examined continuous and jumped casting approaches to the casting of a cylindrical reinforced concrete tank for a sewage-treatment plant, with and without the application of the ‘kicker’ technique in which the lower part of the wall is cast with the slab. The main cause of cracking is thermal change and restraint imposed by adjacent older structures, and the FEM predictions agree well with experimental observations. Continuous casting is most effective at minimizing cracking because it creates only two contact edges between newly cast and existing structures producing the lowest level of restraint. The kicker technique is shown to be very effective for reducing restraint and consider rephasing.
{"title":"Reducing Thermal Crack Risks Caused by Restraint in Young Concrete - A Case Study on Walls of Water Tanks","authors":"Majid Al‐Gburi, J. Jonasson, M. Nilsson","doi":"10.2478/ncr-2022-0001","DOIUrl":"https://doi.org/10.2478/ncr-2022-0001","url":null,"abstract":"Abstract Concrete cracks in structures such as water tanks and nuclear power stations cause anxiety to owners, contractors and engineers. These cracks may significantly increase the structure’s permeability and thus increase leakage, reduce durability, and eventually lead to loss of structural functionality. Therefore it is important to minimize their occurrence and size. To identify effective ways of minimizing cracking in young concrete segments, a parametric study was conducted using the finite element method (FEM). Parameters considered include casting sequence, joint position, wall height, and cooling. The study examined continuous and jumped casting approaches to the casting of a cylindrical reinforced concrete tank for a sewage-treatment plant, with and without the application of the ‘kicker’ technique in which the lower part of the wall is cast with the slab. The main cause of cracking is thermal change and restraint imposed by adjacent older structures, and the FEM predictions agree well with experimental observations. Continuous casting is most effective at minimizing cracking because it creates only two contact edges between newly cast and existing structures producing the lowest level of restraint. The kicker technique is shown to be very effective for reducing restraint and consider rephasing.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"37 1","pages":"41 - 54"},"PeriodicalIF":1.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81380675","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}
Vanessa Saback, C. Popescu, T. Blanksvärd, B. Täljsten
Abstract The need to optimize investments in bridge maintenance has created a demand for improved bridge management systems (BMS). Outdated practices in bridge inspection and constant advances in information technology have also contributed to this demand. The use of Digital Twins (DT), although well established in other industries, is still incipient for asset management and structural analysis of bridges. There is a great deal of research on Building Information Modelling (BIM) for bridge inspection, but its post-construction potential is still under-explored. This study presents a state-of-the-art review of the literature on asset management for bridges using digital models such as BIM and digital twins. The review was conducting using a systematic approach. Despite the rapid increase in research on DT and the amount of existing research on BIM, several gaps remain to be addressed, such as the lack of consensus about the definition of digital twins, which has led to wrongful categorisation of digital models as DT. The complex data flow and software compatibility required to develop a functional DT have hindered the exploitation of their full potential so far. The integration of BIM post-construction to BMS and existing automation technologies can also significantly improve current practices of bridge management.
{"title":"Asset Management of Existing Concrete Bridges Using Digital Twins and BIM: a State-of-the-Art Literature Review","authors":"Vanessa Saback, C. Popescu, T. Blanksvärd, B. Täljsten","doi":"10.2478/ncr-2021-0020","DOIUrl":"https://doi.org/10.2478/ncr-2021-0020","url":null,"abstract":"Abstract The need to optimize investments in bridge maintenance has created a demand for improved bridge management systems (BMS). Outdated practices in bridge inspection and constant advances in information technology have also contributed to this demand. The use of Digital Twins (DT), although well established in other industries, is still incipient for asset management and structural analysis of bridges. There is a great deal of research on Building Information Modelling (BIM) for bridge inspection, but its post-construction potential is still under-explored. This study presents a state-of-the-art review of the literature on asset management for bridges using digital models such as BIM and digital twins. The review was conducting using a systematic approach. Despite the rapid increase in research on DT and the amount of existing research on BIM, several gaps remain to be addressed, such as the lack of consensus about the definition of digital twins, which has led to wrongful categorisation of digital models as DT. The complex data flow and software compatibility required to develop a functional DT have hindered the exploitation of their full potential so far. The integration of BIM post-construction to BMS and existing automation technologies can also significantly improve current practices of bridge management.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"41 1","pages":"91 - 111"},"PeriodicalIF":1.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85533489","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}
Simon Fjendbo, K. De Weerdt, H. Sørensen, M. Geiker
Abstract Due to stochastic and systematic variations in the paste fraction, data for total chloride content are occasionally calibrated using parallelly measured calcium content as a measure of the actual paste fraction − assuming non-calcareous aggregates and no calcium leaching. Data from concrete exposed at the marine Fehmarn Belt Exposure Site questions the latter assumption. In the outer zone experiencing calcium leaching (ten mm after ten years), errors will be introduced by calcium calibration. To account for the wall effect, calcium profiles from cores taken before exposure might be used to correct for the systematically higher paste fraction at cast surfaces.
{"title":"When and How Should Chloride Profiles be Calibrated for Paste Fraction?","authors":"Simon Fjendbo, K. De Weerdt, H. Sørensen, M. Geiker","doi":"10.2478/ncr-2021-0021","DOIUrl":"https://doi.org/10.2478/ncr-2021-0021","url":null,"abstract":"Abstract Due to stochastic and systematic variations in the paste fraction, data for total chloride content are occasionally calibrated using parallelly measured calcium content as a measure of the actual paste fraction − assuming non-calcareous aggregates and no calcium leaching. Data from concrete exposed at the marine Fehmarn Belt Exposure Site questions the latter assumption. In the outer zone experiencing calcium leaching (ten mm after ten years), errors will be introduced by calcium calibration. To account for the wall effect, calcium profiles from cores taken before exposure might be used to correct for the systematically higher paste fraction at cast surfaces.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"17 1","pages":"1 - 18"},"PeriodicalIF":1.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90057173","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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