Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 35) Show all publications
Eriksson, D., Gasch, T. & Ansell, A. (2019). A Hygro-Thermo-Mechanical Multiphase Model for Long-Term Water Absorption into Air-Entrained Concrete. Transport in Porous Media, 127(1), 113-141
Open this publication in new window or tab >>A Hygro-Thermo-Mechanical Multiphase Model for Long-Term Water Absorption into Air-Entrained Concrete
2019 (English)In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 127, no 1, p. 113-141Article in journal (Refereed) Published
Abstract [en]

Many concrete structures located in cold climates and in contact with free water are cast with air-entrained concrete. The presence of air pores significantly affects the absorption of water into the concrete, and it may take decades before these are fully saturated. This generally improves the long-term performance of such structures and in particular their frost resistance. To study the long-term moisture conditions in air-entrained concrete, a hygro-thermo-mechanical multiphase model is presented, where the rate of filling of air pores with water is described as a separate diffusion process. The driving potential is the concentration of dissolved air, obtained using an averaging procedure with the air pore size distribution as the weighting function. The model is derived using the thermodynamically constrained averaging theory as a starting point. Two examples are presented to demonstrate the capabilities and performance of the proposed model. These show that the model is capable of describing the complete absorption process of water in air-entrained concrete and yields results that comply with laboratory and in situ measurements.

Place, publisher, year, edition, pages
Netherlands: Springer, 2019
Keywords
Air-entrained concrete, Multiphase model, Long-term absorption, Diffusion, Pore size distribution
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-240364 (URN)10.1007/s11242-018-1182-3 (DOI)000459472600005 ()2-s2.0-85055973654 (Scopus ID)
Note

QC 20190108

Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2019-03-19Bibliographically approved
Šmilauer, V., Havlásek, P., Gasch, T., Delaplace, A., Bouhjiti, D.-M. E., Benboudjema, F., . . . Azenha, M. (2019). Hygro-mechanical modeling of restrained ring test: COST TU1404 benchmark. Construction and Building Materials, 229, Article ID 116543.
Open this publication in new window or tab >>Hygro-mechanical modeling of restrained ring test: COST TU1404 benchmark
Show others...
2019 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 229, article id 116543Article in journal (Refereed) Published
Abstract [en]

The restrained ring test belongs to a traditional method for estimating cracking tendency of a paste, mortar or concrete mix. The test involves hygro-mechanical interactions with intricate interplay of several phenomena, such as autogenous shrinkage, drying shrinkage, basic and drying creep, together with evolution of tensile strength and fracture energy. The benchmark described in this paper relies on extensive experimental data sets obtained through the extended Round Robin Testing programme (RRT+) of COST Action TU1404. Six teams took part with their simulation models. A series of outputs were produced, starting from mass loss of a prism through its axial deformation up to hoop stress/strain evolution in the ring. Four teams quantified also damage due to drying and strain concentrations. All models showed excellent performance on mass loss while strain validation showed higher scatter and influence of several factors. The benchmark demonstrated high capability of used models and emphasized strong role of calibration with regards to available experimental data.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Crack, Creep, Hygro-mechanical simulation, Moisture, Restrained ring test, Shrinkage, Transport, Cracks, Drying, Tensile strength, Autogenous shrinkage, Axial deformations, Drying shrinkages, Mechanical interactions, Mechanical simulations, Restrained ring, Strain concentration
National Category
Building Technologies
Research subject
Civil and Architectural Engineering, Concrete Structures
Identifiers
urn:nbn:se:kth:diva-263458 (URN)10.1016/j.conbuildmat.2019.07.269 (DOI)2-s2.0-85071874931 (Scopus ID)
Note

QC 20191205

Available from: 2019-12-05 Created: 2019-12-05 Last updated: 2019-12-05Bibliographically approved
Gasch, T. (2019). Multiphysical analysis methods to predict the ageing and durability of concrete. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Multiphysical analysis methods to predict the ageing and durability of concrete
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With the societal demand for sustainability and the increasing age of infrastructure, a crucial task for the civil engineering community is to improve the durability of concrete structures. This thesis aims to contribute to such development through theoretical studies using mathematical modelling and numerical simulations. During its service life, a concrete structure is subjected to many different actions, ranging from mechanical loads to chemical and physical processes. Hence, a sound modelling strategy requires multiphysics and the inclusion of coupled chemical and physical fields (e.g. temperature, moisture and cement hydration) in addition to methods that describe mechanical integrity of the material. Conditions and phenomena critical for concrete structures at hydropower facilities have been of particular interest to study.

The thesis presents several mathematical models of various complexity to describe the multiphysical behaviour of concrete using a material point description. A significant focus is on models that describe the mechanical behaviour of concrete where aspects such as ageing, cracking, creep and shrinkage are investigated. For the creep behaviour, a state-of-the-art model based on the Microprestress–Solidification (MPS) theory is reviewed and further developed. The appended papers (III to IV) presents a mathematical framework for the modelling of durability aspects of concrete based on multiphase porous media theory. The governing equations are derived with the Thermodynamically Constrained Averaging Theory (TCAT) as a starting point. It is demonstrated how this framework can be applied to a broad variety of phenomena related to durability; from the casting and hardening of concrete to the long-term absorption of water into air-entrained concrete. The Finite Element Methods (FEM) is used to solve the proposed mathematical models, and their capabilities are verified using experimental data from the literature.

The main research contribution is the development and evaluation of theoretical models that advance the understanding and improve knowledge of the ageing and durability of concrete and concrete structures. More precisely, it is shown how multiphysical models and the developed multiphase framework can be used to gain insights on the material behaviour of concrete at smaller scales while they are also applicable to structural-scale simulations. During all model development, the efficient solution of structural problems has been fundamental. Through case studies and several examples from the literature, it is exemplified how these models can be used to enhance the performance and thereby increase the durability of concrete structures.

Abstract [sv]

I och med samhällets krav på hållbarhet och den ökande åldern på infrastrukturkonstruktioner är en avgörande uppgift för byggindustrin att förbättra betongkonstruktioners beständighet. Syftet med denna avhandling är att bidra till en sådan utveckling genom teoretiska studier med hjälp av matematisk modellering och numeriska simuleringar. En betongkonstruktion utsätts under sin livslängd för många olika mekaniska laster samt fysikaliska och kemiska processer. Ett sunt tillvägagångsätt gällande modellering kräver därför multifysik och kopplade fysikaliska och kemiska fält (t.ex. temperatur, fukt och cementhydratisering) beaktas utöver de metoder som beskriver materialets mekaniska hållfasthet. Sådana förutsättningar och fenomen som är kritiska för betongkonstruktioner vid vattenkraftsanläggningar är av särskilt intresse att studera.

Avhandling presenterar ett flertal matematiska modeller av varierande komplexitet baserade på en materialpunktsbeskrivning av betongens multifysikaliska beteende. En tonvikt ligger på modeller som beskriver betongens mekaniska beteende där aspekter som åldrande, sprickbildning, krypning och krympning undersöks. Gällande krypning har en state-of-the-art modell baserad på  “Microprestress–Solidification (MPS )” teorin studerats och vidareutvecklats. I de bilagda artiklarna (III till V) presenteras ett matematiskt ramverk för att beskriva fenomen relaterade till betongens beständighet. Detta ramverk baseras på en multifas beskrivning av porösa material, där de styrande ekvationerna är härledda utifrån “Thermodynamically Constrained Averaging Theory (TCAT)”. Det exemplifieras hur detta ramverk kan tillämpas på en rad olika fenomen relaterade till beständighet. Dessa sträcker sig från gjutning och hårdnande av betong till absorption av vatten till lufttillsatt betong. För att lösa de presenterade matematiska modellerna tillämpas den finita elementmetoden (FEM) och de numeriska lösningarna verifieras med hjälp av experimentella resultat från litteraturen.

Avhandlingens huvudsakliga forskningsbidrag är utveckling och utvärdering av teoretiska modeller som ökar förståelsen och förbättrar kunskapen om betong- och betongkonstruktioners åldrande och beständighet. Mer specifikt visas hur multifysiska modeller och det utvecklade multifas modellerna kan användas till att studera betongmaterialets beteende samtidigt som de också är användbara för simuleringar på strukturskala. En effektiv lösning av strukturproblem har varit viktig under all modellutveckling. I olika fallstudier och experiment från litteraturen exemplifieras hur dessa modeller kan användas för att förbättra betongkonstruktioners funktion och därigenom öka dess beständighet.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 123
Series
TRITA-ABE-DLT ; 1910
Keywords
Ageing, Cracking, Creep, Concrete, Durability, Finite Element Method, Multiphysics, Shrinkage, Beständighet, Betong, Finita elementmetoden, Krypning, Krympning, Multifysik, Sprickbildning, Åldring
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-246147 (URN)978-91-7873-145-9 (ISBN)
Public defence
2019-04-11, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20190315

Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2019-03-15Bibliographically approved
Gasch, T., Malm, R. & Ansell, A. (2019). Three-dimensional simulations of ageing concrete structures using a multiphase model formulation. Materials and Structures, 52(4), Article ID 85.
Open this publication in new window or tab >>Three-dimensional simulations of ageing concrete structures using a multiphase model formulation
2019 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, no 4, article id 85Article in journal (Refereed) Published
Abstract [en]

The durability of concrete structures is in no small degree determined by the quality and integrity of the concrete, where structural damages such as cracks negatively affect many of the functions of the structure. Often cracks are formed due to restrained thermal and hygral deformations, where the risk is exceptionally high during the early stages after casting. This study presents a hygro-thermo-chemo-mechanical model that accounts for phenomena such as hydration, external and internal drying, self-heating, creep, shrinkage and fracture. The model is derived as a modified version of a fully-coupled multiphase model recently proposed by Gasch et al. (Cem Concrete Res 116:202–216, 2019. https://doi.org/10.1016/j.cemconres.2018.09.009) and implemented in the Finite Element Method. Here the governing equations are simplified, and a more efficient solution method is proposed. These modifications are made with the intention to obtain a model more suitable for structural scale simulations. To validate the model, one of the end-restrained beams tested within the French research project CEOS.fr is analyzed. Laboratory data on the concrete is used to calibrate to model and recordings of ambient conditions makes it possible to define accurate boundary conditions. Results from the simulation are compared to measured temperatures and deformations from the first 60 days after casting and are found to generally be in good agreement. Compared to the fully-coupled model by Gasch et al. (2019), the modifications proposed in this study reduce the computational cost by a factor five; without any noticeable differences to the structural results.

Place, publisher, year, edition, pages
Springer Netherlands, 2019
Keywords
Concrete, Early-age, Finite Element Method, Hygro-thermo-chemo-mechanical, Structural application
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-262551 (URN)10.1617/s11527-019-1383-4 (DOI)000478086000001 ()2-s2.0-85069913179 (Scopus ID)
Note

QC 20191021

Available from: 2019-10-21 Created: 2019-10-21 Last updated: 2019-10-21Bibliographically approved
Eriksson, D., Gasch, T., Malm, R. & Ansell, A. (2018). Freezing of partially saturated air-entrained concrete: A multiphase description of the hygro-thermo-mechanical behaviour. International Journal of Solids and Structures, 152-153, 294-304
Open this publication in new window or tab >>Freezing of partially saturated air-entrained concrete: A multiphase description of the hygro-thermo-mechanical behaviour
2018 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 152-153, p. 294-304Article in journal (Refereed) Published
Abstract [en]

Even though air-entrained concrete is usually used for concrete structures located in cold climates that are exposed to wet environments, frost damage is frequently detected during inspections. However, it is often hard to assess the extent and severity of the damage and, thus, there is a need for better tools and aids that can complement already established assessment methods. Several studies have successfully shown that models based on poromechanics and a multiphase approach can be used to describe the freezing behaviour of air-entrained concrete. However, these models are often limited to the scale of the air pore system and, hence, hard to use in applications involving real structures. This study proposes a hygro-thermo-mechanical multiphase model which describes the freezing behaviour of partially saturated air-entrained concrete on the structural scale. The model is implemented in a general FE-code and two numerical examples are presented to validate and show the capabilities of the model. The first concerns a series of experimental tests of air-entrained cement pastes, whereas the second aims to show the capability of the model to account for an initial non-uniform distribution of moisture. While the model predictions underestimate the magnitude of the measured strains, the results still show that the model can capture the general freezing behaviour observed in the experimental tests on the structural scale. Furthermore, the results demonstrate that the model is capable of describing freezing induced deformations caused by non-uniform moisture distributions.

Keywords
Freezing, Partially saturated, Air-entrained concrete, Structural scale, Finite element modelling
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-237303 (URN)10.1016/j.ijsolstr.2018.07.004 (DOI)000447576100023 ()2-s2.0-85051402406 (Scopus ID)
Note

QC 20181114

Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2019-01-07Bibliographically approved
Eriksson, D. & Gasch, T. (2018). Influence of air voids in multiphase modelling for service life prediction of partially saturated concrete. In: Günther Meschke, Bernhard Pichler, Jan G. Rots (Ed.), Computational Modelling of Concrete Structures: . Paper presented at Euro-C 2018 Computational Modelling of Concrete and Concrete Structures (pp. 317-326). London, UK: CRC Press
Open this publication in new window or tab >>Influence of air voids in multiphase modelling for service life prediction of partially saturated concrete
2018 (English)In: Computational Modelling of Concrete Structures / [ed] Günther Meschke, Bernhard Pichler, Jan G. Rots, London, UK: CRC Press, 2018, p. 317-326Conference paper, Published paper (Refereed)
Abstract [en]

The purpose of this study is to show the influence and significance of including water filling of air pores when studying moisture conditions in concrete structures cast with air-entrained concrete and in contact with free water. Especially if the aim is to assess the risk for frost damages in different regions of the structure, based on a critical degree of saturation, in order to ultimately perform a service life prediction. A hygro-thermo-mechanical multiphase model that includes the effect of water filling in air pores, recently presented by the authors, is briefly described and applied in two numerical examples. The results show moisture distributions that would not be possible to capture without the air pore filling included in the model. More importantly, the general shape of these distributions complies well with measured distributions in real concrete structures as well as with distributions obtained in laboratory measurements.

Place, publisher, year, edition, pages
London, UK: CRC Press, 2018
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-225113 (URN)2-s2.0-85061340478 (Scopus ID)978-1-138-74117-1 (ISBN)978-1-315-18296-4 (ISBN)
Conference
Euro-C 2018 Computational Modelling of Concrete and Concrete Structures
Note

QC 20180403

Available from: 2018-03-29 Created: 2018-03-29 Last updated: 2019-04-26Bibliographically approved
Gasch, T., Ahmed, L. & Malm, R. (2018). Instrumentation and Modelling of a Reactor Containment Building. Energiforsk
Open this publication in new window or tab >>Instrumentation and Modelling of a Reactor Containment Building
2018 (English)Report (Other academic)
Abstract [en]

Nuclear concrete containment buildings typically consist of pre-stressed concrete. The pre-stressing tendons are utilized to enforce a compressive state of stress to ensure that cracks do not occur in the containment structure. The tendons are thereby an important part of the containment building and important for its structural integrity. In many cases, these tendons are grouted with cement grout to prevent corrosion. This results however in that it is not possible to directly assess the tendons or re-tension these if significant long term losses occurs. The drawback with cement grouted tendons is, thereby, that it is not possible to directly measure the current tendon force. One conventional method to assess the status of the containment building, and thereby indirectly the tendons, is to perform pressure tests. The pressure tests are performed where the pressure in the containment building is increased. The response of the containment can after this be determined based on measurements of displacements and strains. The purpose of this project is to perform simulations of a pressure test of a Boiling Water Reactor (BWR) that is common in Sweden and Finland. Based on these simulations, the response of the containment building is determined and suggestions are made regarding suitable placement of measuring sensors. The suggested instrumentation has been divided into different types of sensors defined as detectors and support sensors. The detectors are needed to monitor the structural response of the containment while the support sensors are needed to give sufficient input to numerical analyses. It is suggested that detector sensors are placed at four vertical positions and at three points along the perimeter. At these locations, it is recommended that displacement sensors, strain gauges and temperature sensors are installed. In addition, it is also recommended that the relative radial displacement between the intermediate slab and the cylinder wall is monitored. As support sensors, it is recommended that the ambient temperature and relative humidity is measured since these constitute important boundary conditions for numerical analyses and thereby prediction of the structural behaviour.

Place, publisher, year, edition, pages
Energiforsk, 2018. p. 50
Series
Energiforsk report ; 2018:526
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-235725 (URN)978-91-7673-526-8 (ISBN)
Note

QC 20181009

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-10-09Bibliographically approved
Smilauer, V., Gasch, T., Delaplace, A., Bouhjiti, D., Kanavaris, F., Azenha, M. & Lacarriere, L. (2018). Macroscopic hygro-mechanical modeling of restrained ring test - Results from COST TU1404 benchmark. In: Miguel Azenha, Dirk Schlicke, Farid Benboudjema, Agnieszka Jedrzejewska (Ed.), : . Paper presented at International conference on Interdisciplinary Approaches for Cement-based Materials and Structural Concrete (SynerCrete'18), Funchal, Portugal, October 24-26, 2018 (pp. 79-84). Paris: Rilem Publications
Open this publication in new window or tab >>Macroscopic hygro-mechanical modeling of restrained ring test - Results from COST TU1404 benchmark
Show others...
2018 (English)In: / [ed] Miguel Azenha, Dirk Schlicke, Farid Benboudjema, Agnieszka Jedrzejewska, Paris: Rilem Publications , 2018, p. 79-84Conference paper, Published paper (Refereed)
Abstract [en]

The restrained ring test under constant temperature is used for estimating cracking tendency of pastes, mortar or concrete. This test induces hygro-mechanical interactions, with intricate interplay of several phenomena such as autogenous shrinkage, drying shrinkage, basic and drying creep, as well as evolution of tensile strength and fracture energy. The benchmark described in this paper relies on extensive experimental data sets obtained through the extended Round Robin Testing programme (RRT+) of COST Action TU1404. Five teams took part with their simulation models. A series of outputs were produced, starting from mass loss of a prism through its axial deformation up to stress/strain evolution in the ring. Three teams quantified also damage due to drying and stress concentration around a ring’s notch. All models showed excellent performance on mass loss while strain validation showed higher scatter and influence of several other factors. The benchmark demonstrated high capability of used models and emphasized strong role of calibration with regards to available experimental data.

Place, publisher, year, edition, pages
Paris: Rilem Publications, 2018
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering, Concrete Structures
Identifiers
urn:nbn:se:kth:diva-260979 (URN)10.5281/zenodo.1405563 (DOI)978-2-35158-202-2 (ISBN)978-2-35158-203-9 (ISBN)
Conference
International conference on Interdisciplinary Approaches for Cement-based Materials and Structural Concrete (SynerCrete'18), Funchal, Portugal, October 24-26, 2018
Note

QC 20191029

Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-10-29Bibliographically approved
Eriksson, D. & Gasch, T. (2017). Comparison of mechanistic and phenomenological approaches to model drying shrinkage of concrete. In: Marianne Tange Hasholt (Ed.), Nordic Concrete Research: Proceedings of the XXIII Nordic Concrete Research Symposium. Paper presented at XXIII Nordic Concrete Research Symposium (pp. 287-290).
Open this publication in new window or tab >>Comparison of mechanistic and phenomenological approaches to model drying shrinkage of concrete
2017 (English)In: Nordic Concrete Research: Proceedings of the XXIII Nordic Concrete Research Symposium / [ed] Marianne Tange Hasholt, 2017, p. 287-290Conference paper, Published paper (Refereed)
Abstract [en]

Drying shrinkage of concrete is often estimated using a phenomenological approach where it is assumed that shrinkage is proportional to the change in internal humidity. In this study, a mechanistic approach was used which instead aims to mathematically describe the physical processes of drying shrinkage. Simulations of two laboratory tests were made and compared to results from two models based on the phenomenological approach. The results show that the developed model can describe drying shrinkage of concrete equally well as the phenomenological models but without the need to specify the final drying shrinkage strain.

Keywords
Creep, Modelling, Shrinkage, Multiphase Porous Media, Mechanistic approach
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-235272 (URN)
Conference
XXIII Nordic Concrete Research Symposium
Note

QC 20181003

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-10-03Bibliographically approved
Bernstone, C., Gasch, T., Åhs, M. & Malm, R. (2017). Verifiering av struktur och fuktmekaniska beräkningsverktyg.
Open this publication in new window or tab >>Verifiering av struktur och fuktmekaniska beräkningsverktyg
2017 (Swedish)Report (Other academic)
Publisher
p. 49
Series
Energiforsk report ; 2017:432
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:kth:diva-235737 (URN)978-91-7673-432-2 (ISBN)
Note

QC 20181009

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-10-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8000-6781

Search in DiVA

Show all publications