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Hedlund, Hans
Publications (10 of 58) Show all publications
Rajczakowska, M., Habermehl-Cwirzen, K., Hedlund, H. & Cwirzen, A. (2019). Autogenous Self-Healing: A Better Solution for Concrete. Journal of materials in civil engineering, 31(9), Article ID 3119001.
Open this publication in new window or tab >>Autogenous Self-Healing: A Better Solution for Concrete
2019 (English)In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 31, no 9, article id 3119001Article in journal (Refereed) Published
Abstract [en]

Self-healing can be defined as the ability of a material to repair inner damage without any external intervention. In the case of concrete, the process can be autogenous, based on optimized mix composition, or autonomous, when using additionally incorporated capsules containing a healing agent and/or bacteria spores. The first process uses unhydrated cement particles as the healing material while the other utilizes a synthetic material or bacteria released into the crack from a broken capsule or activated through access of water and oxygen. The critical reviewing of both methods indicates that the autogenous self-healing is more efficient, more cost effective, safer, and easier to implement in full-scale applications. Nevertheless, a better understanding of the mechanism and factors affecting the effectiveness of the process is needed. The main weaknesses of the autonomous method were identified as loss of workability, worsened mechanical properties, low efficiency and low probability of the healing to occur, low survivability of the capsules and bacteria in harsh concrete environment, very high price, and lack of full-scale evaluation.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2019
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-75206 (URN)10.1061/(ASCE)MT.1943-5533.0002764 (DOI)000475694700023 ()2-s2.0-85067520596 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-07-03 (svasva)

Available from: 2019-07-03 Created: 2019-07-03 Last updated: 2019-08-16Bibliographically approved
Sayahi, F., Emborg, M., Hedlund, H. & Cwirzen, A. (2019). Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period. Nordic Concrete Research, 60(1), 67-88
Open this publication in new window or tab >>Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period
2019 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 60, no 1, p. 67-88Article in journal (Refereed) Published
Abstract [en]

This research investigates the effect of capillary pressure and the length of the hydration dormant period on the plastic shrinkage cracking tendency of SCC by studying specimens produced with different w/c ratios, cement types and SP dosages.

The results show, that the cracking tendency of SCC was the lowest in case of w/c ratio between 0.45 and 0.55, finer rapid hardening cement and lower dosage of SP. The dormant period was prolonged by increasing the w/c ratio, using coarser cement and higher SP dosage. It was concluded that the cracking tendency of concrete is a function of the capillary pressure build-up rate and the length of the dormant period.

Place, publisher, year, edition, pages
Norsk betongförening, 2019
Keywords
plastic shrinkage, cracking, evaporation, capillary pressure, dormant period, self-compacting concrete.
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-73170 (URN)10.2478/ncr-2019-0012 (DOI)000475508100006 ()
Note

Validerad;2019;Nivå 2;2019-07-23 (svasva)

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-08-16Bibliographically approved
Sayahi, F., Emborg, M. & Hedlund, H. (2017). Effect of Water-Cement Ratio on Plastic Shrinkage Cracking in Self-Compacting Concrete. In: Proceedings of the 23rd Nordic Concrete Research Symposium: . Paper presented at 23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017. Oslo, Norway: Nordic Concrete Federation
Open this publication in new window or tab >>Effect of Water-Cement Ratio on Plastic Shrinkage Cracking in Self-Compacting Concrete
2017 (English)In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper, Published paper (Refereed)
Abstract [en]

Plastic shrinkage cracking is a mechanical phenomenon that occurs in the first few hours after casting the concrete in its mould. It is commonly believed that rapid and excessive moisture loss of the fresh concrete, mainly due to evaporation, plays a decisive role in the early age shrinkage. However, it is not always possible to justify all the plastic shrinkage incidents based on water evaporation solely. Instead, it seems that and interconnected correlation between evaporation, capillary pressure and hydration rate may offer better explanation. In this paper effect of water-cement (w/c) ratio on plastic shrinkage cracking of self-compacting concrete (SCC) is investigates. Four recipes with different w/c ratios (0.38, 0.45, 0.55 and 0.67) are tested by using Ring test method (NT BUILD 433). During the experiments evaporation, capillary pressure and internal temperature of the specimens were recorded from 60 minutes after casting up to 18 hours, at which the length and width of the cracks were measured. The results show lower risk of cracking when w/c ratio is between 0.45 to 0.55. However, the specimens with 0.38 and 0.67 w/c ratio experienced higher cracking tendency, especially the latter, in which severe cracking was observed.

Place, publisher, year, edition, pages
Oslo, Norway: Nordic Concrete Federation, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65992 (URN)978-82-8208-056-9 (ISBN)
Conference
23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2018-03-28Bibliographically approved
Sayahi, F., Emborg, M. & Hedlund, H. (2017). Plastic Shrinkage Cracking in Concrete: Influence of Test Methods. In: : . Paper presented at 2nd International RILEM/COST Conference on Early Age Cracking and Serviceability in Cement-based Materials and Structures - EAC2, Brussels, Belgium, 12–14 September 2017.
Open this publication in new window or tab >>Plastic Shrinkage Cracking in Concrete: Influence of Test Methods
2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Plastic shrinkage cracking can become problematic especially in concrete elements with high surface to volume ratio such as slabs and pavements. In this paper two test methods commonly used when studying the phenomenon have been evaluated; ring test method (NORDTEST-method NT Build 433) developed in NTNU/SINTEF by Johansen and Dahl in order to study the effect of different materials and constituents on the cracking tendency at macro-level, and ASTM C 1579, mainly designed in order to map the influence of fibres. During this research, influence of coarse aggregate content on plastic shrinkage cracking of self-compacting concrete (SCC) was studied. Preliminary results show same tendencies with the two methods i.e. a lower plastic shrinkage tendency with higher amount of coarse aggregates.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65993 (URN)
Conference
2nd International RILEM/COST Conference on Early Age Cracking and Serviceability in Cement-based Materials and Structures - EAC2, Brussels, Belgium, 12–14 September 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2018-03-28Bibliographically approved
Sayahi, F., Emborg, M., Hedlund, H. & Löfgren, I. (2016). PLASTIC SHRINKAGE CRAKING IN SELF-COMPACTING CONCRETE: A PARAMETRIC STUDY (ed.). In: (Ed.), Miguel Azenha; Ivan Gabrijel; Dirk Schlicke; Terje Kanstad; Ole Mejhede Jensen (Ed.), International RILEM conference on Materials, Systems and Structures in Civil Engineering 2016 (MSSCE 2016): Service Life of Cement-Based Materials and Structures. Paper presented at MSSCE2016 : RILEM 22/08/2016 (pp. 609-619). Paris, France: Rilem publications, 2
Open this publication in new window or tab >>PLASTIC SHRINKAGE CRAKING IN SELF-COMPACTING CONCRETE: A PARAMETRIC STUDY
2016 (English)In: International RILEM conference on Materials, Systems and Structures in Civil Engineering 2016 (MSSCE 2016): Service Life of Cement-Based Materials and Structures / [ed] Miguel Azenha; Ivan Gabrijel; Dirk Schlicke; Terje Kanstad; Ole Mejhede Jensen, Paris, France: Rilem publications, 2016, Vol. 2, p. 609-619Conference paper, Published paper (Refereed)
Abstract [en]

Plastic shrinkage cracking, often the first type of cracks occurring even before initial setting, causes enormous expenses for the building industry annually. The main reason behind the phenomenon is believed to be rapid and excessive surface water evaporation of the concrete element in the plastic stage which in turn leads to the so-called plastic or capillary shrinkage. These cracks mainly occur in horizontal concrete elements with large surface to volume ratio (such as slabs, pavements, etc.). This paper reports results from experiments performed, using ring test method (NORDTEST-method NT Build 433). During the experiments, influence of water-cement (w/c) ratio, cement type, coarse aggregate content and super plasticizer dosage was investigated. Moreover, effort was made to explain the difference in cracking tendency of different concretes based on water evaporation rate and capillary pressure. It seems that various parameters have different influences on the cracking tendency, the evaporation rate, as well as the hydration rate and capillary pressure. Although, capillary pressure is local and its maximum value differs in different locations, it seems that its development rate, especially in the first few hours, is almost identical everywhere in the specimen. This may be used as a plastic shrinkage indicator.

Place, publisher, year, edition, pages
Paris, France: Rilem publications, 2016
Keywords
Plastic Shrinkage, Cracking, Evaporation, Capillary pressure, Dormant period, NORDTEST-method NT Build 433, Materials science - Construction materials, Teknisk materialvetenskap - Konstruktionsmaterial
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-35371 (URN)9e2dae36-20fb-4d92-9733-2793d99619a6 (Local ID)978-2-35158-170-4 (ISBN)978-2-35158-173-5 (ISBN)9e2dae36-20fb-4d92-9733-2793d99619a6 (Archive number)9e2dae36-20fb-4d92-9733-2793d99619a6 (OAI)
Conference
MSSCE2016 : RILEM 22/08/2016
Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2019-03-04Bibliographically approved
Hösthagen, A., Jonasson, J.-E., Emborg, M. & Hedlund, H. (2014). Equivalent Restraint Method Correlated to Empirical Measurements (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 505-508
Open this publication in new window or tab >>Equivalent Restraint Method Correlated to Empirical Measurements
2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 505-508Article in journal (Refereed) Published
Abstract [en]

The present study deals with the correlation between numerical models and empirical observations in newly cast concrete specimens. The model used is the equivalent restraint method, ERM, which is established from several local restraint method calculations, LRM. The csating of walls in a tunnel construction is investigated. Correlation between models and empirical measurements is established in three steps.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-27616 (URN)11cbb2cf-a35e-4581-a829-d06f7ee33a63 (Local ID)11cbb2cf-a35e-4581-a829-d06f7ee33a63 (Archive number)11cbb2cf-a35e-4581-a829-d06f7ee33a63 (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140830 (mem); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-20Bibliographically approved
Orosz, K., Fjellström, P., Jonasson, J.-E., Emborg, M. & Hedlund, H. (2014). Evaluation of the Linear Logarithmic Creep Model (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 417-420
Open this publication in new window or tab >>Evaluation of the Linear Logarithmic Creep Model
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2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 417-420Article in journal (Refereed) Published
Abstract [en]

In order to make reliable predictions of thermal cracking risks in young concrete, modelling of the creep behaviour is important. The linear logarithmic creep model (LLM) has only been used to describe the creep behaviour of moisture-sealed concrete samples (basic creep). The aim of the present research is to check whether LLM could be also applied to drying creep. The results indicate that the LLM delivers good results for sealed but not for drying samples. Thus, refinement of the existing model (e.g., tri-linear instead of bi-linear in logarithmic time scale), or a new model is needed to account for the increase of creep due to on-going drying.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-28345 (URN)21e99458-34c1-4122-8238-0b6afbf87fe3 (Local ID)21e99458-34c1-4122-8238-0b6afbf87fe3 (Archive number)21e99458-34c1-4122-8238-0b6afbf87fe3 (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140829 (katoro); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-25Bibliographically approved
Orosz, K., Fjellström, P., Jonasson, J.-E., Emborg, M. & Hedlund, H. (2014). Evaluation of Thermal Dilation and Autogenous Shrinkage at Sealed Conditions (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 299-302
Open this publication in new window or tab >>Evaluation of Thermal Dilation and Autogenous Shrinkage at Sealed Conditions
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2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 299-302Article in journal (Refereed) Published
Abstract [en]

As known, load independent deformations are of large importance in structural analysis, e. g. when estimating elongations, restraint stresses, or pre-stressing forces. Two models to describe thermal dilation (TD) and autogenous shrinkage (AS) have been evaluated, for a broader range of w/C ratios and cements types than before. In Model I, AS is determined solely based on the maturity model and TD incorporates two TD coefficients (TDC). In Model II, AS is dependent on both the maturity model and a separate temperature adjustment factor, while TDC is constant. For the more rapid-hardening cement, Model I did not give satisfactory results, whereas the usefulness of Model II to describe both AS and TD has shown to be limited, suggesting that a new model is needed.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-31101 (URN)529e1b20-d576-493d-8f5d-c5c22c0395de (Local ID)529e1b20-d576-493d-8f5d-c5c22c0395de (Archive number)529e1b20-d576-493d-8f5d-c5c22c0395de (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140829 (katoro); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-25Bibliographically approved
Jonasson, J.-E., Emborg, M. & Hedlund, H. (2014). Measurement and modelling of strength and heat of hydration for young concrete (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 501-504
Open this publication in new window or tab >>Measurement and modelling of strength and heat of hydration for young concrete
2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 501-504Article in journal (Refereed) Published
Abstract [en]

Strength development and heat evolution at hydration are two of the most important properties when analysing concrete structures concerning young concrete. The present model for strength development is shown to properly predict the strength development for high early temperatures during hardening stage. The detemination of heat of hydration based on semi-adiabatic test has been refined with respect to the warming up the test equipment.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-32227 (URN)6a6eef6f-bca3-4f05-8e31-7a3b85cc9430 (Local ID)6a6eef6f-bca3-4f05-8e31-7a3b85cc9430 (Archive number)6a6eef6f-bca3-4f05-8e31-7a3b85cc9430 (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140830 (mem); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-26Bibliographically approved
Jonasson, J.-E., Nilsson, L.-O., Emborg, M. & Hedlund, H. (2014). Moisture and mechanical properties aimed for crack risk analyses if early age concrete (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 409-412
Open this publication in new window or tab >>Moisture and mechanical properties aimed for crack risk analyses if early age concrete
2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 409-412Article in journal (Refereed) Published
Abstract [en]

Within the project Crack-Free-Con - Nordic coordination for sustainable construction by novel shrinkage modelling and user friendly Expert System - a collaborative project between research area of Building Material at LTH and Structural Engineering at LTU a comprehensive test program has been performed. The tests at LTH are concentrated on moisture related properties while the tests at LTU cover mechanical properties and stress development. At present the interesting work to combine the test results from the laboratories are in progress

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-33043 (URN)7ca3e215-2325-415a-89cc-88f6ba73be85 (Local ID)7ca3e215-2325-415a-89cc-88f6ba73be85 (Archive number)7ca3e215-2325-415a-89cc-88f6ba73be85 (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140830 (mem); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-26Bibliographically approved
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