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  • 1.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Rajczakowska, Magdalena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography2020In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 72, no 2, p. 88-96Article in journal (Refereed)
    Abstract [en]

    The specific surface area (SSA) of constituents in a concrete mixture has a significant effect on its workability in fresh state. Excess layer theories relate the SSA to the flow behaviour of mixtures and can be used as part of an approach to mix design. However, measurement of SSA is complex and includes several issues, and thus is commonly replaced by mathematical estimation of the parameter. The mathematical approximation of surface area is based on the assumption of a spherical shape for the particles, which leads to failure of taking into account the effect of shape and the square–cube law. The article explores the possibility of replacing the assumption of a spherical shape with that of Platonic solids as the representative shape to account for the angularity of aggregates. The calculation was conducted based on information on the particle size distribution (PSD) obtained from dry sieving method. A calculated surface area on the assumption of a dodecahedron shape for natural aggregates and a cubical shape for crushed aggregates showed good agreement with SSA measurements conducted by X-ray microtomography. Furthermore, the effect of changes in PSD on the accuracy of the approach was also studied. It was found that the estimated value of SSA was improved in comparison with the traditional way of calculation on the assumption of a spherical shape.

  • 2.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A theoretical study on optimal packing in mortar and paste2019In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605Article in journal (Refereed)
    Abstract [en]

    Packing density of particles is regarded as a key factor affecting workability of cementitious mixtures. While the value can be easily measured, and several models exist for estimating the parameter, no generally accepted definition exist for the optimal packing. Current study aims at exploring the concept of optimal packing in mortars and paste using particle packing and excess water layer theories. A semiempirical method is used for calculating water demand of mixtures based on their specific surface area. The approach allows for estimating optimal packing considering water demand and water to cement ratio of mixtures in addition to packing density. 

  • 3.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Betongindustri AB, Stockholm, Sweden.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Effect of water film thickness on the flow in conventional mortars and concrete2019In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, no 3, article id 62Article in journal (Refereed)
    Abstract [en]

    Mortar and concrete can be divided into two phases of solids and water where water fills the voids between the grains and also coats the surface of particles. The current study investigates the influence of the thickness of coating water on flow spread of mortars and concretes. The article aims at correlating consistency of concretes to consistency of mortars. It was found that the flow behavior of granular mixtures can be directly related to the average water film thickness that envelops the particles. The concept was tested on mortar and concrete mixtures with different cement types, aggregate grading, aggregate shape, fineness and proportioning; proving water film thickness to be the most critical parameter affecting the flow. The results of the study indicate the possibility of predicting the flowability of mixtures by knowing the enveloping water film thickness. In addition, the relation between flowability of mixtures measured in different sizes of slump cone is explored to enable translating flow of mortars measured in mini-slump cone to flow of concrete obtained from Abram’s cone.

  • 4.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Exploring the relation between the flow of mortar and specific surface area of its constituents2019In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 211, p. 492-501Article in journal (Refereed)
    Abstract [en]

    Mortars can be studied as mixtures of solid and flowable phases. The volume of the flowable phase required for deformation depends on the solid phase surface area according to excess layer theories. This paper examines the relation between the specific surface area of constituents in mortars and their flow. The flowable phase volume was divided by the solid phase surface area to obtain the layer thickness surrounding the surface of the particles. The results suggested that the amount of water and paste needed to ensure flow could be estimated from the packing density and specific surface area of the particles.

  • 5.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period2019In: Nordic Concrete Research, ISSN 0800-6377, Vol. 60, no 1, p. 67-88Article in journal (Refereed)
    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.

  • 6.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Stelmarczyk, Marcin
    The Severity of Plastic Shrinkage Cracking in Concrete: A New Model2019In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763XArticle in journal (Refereed)
    Abstract [en]

    Plastic shrinkage cracking in concrete is mainly a physical process, in which chemical reactions between cement and water do not play a decisive role. It is commonly believed that rapid and excessive moisture loss, due to evaporation is the primary cause of the phenomenon. This paper presents a new model to estimate the severity of plastic shrinkage cracking, based on the initial setting time and the amount of the evaporated water from within the concrete bulk. A number of experiments were performed under controlled ambient conditions, during which the water-cement ratio, cement type, and the dosage of superplasticizer were altered. The results, alongside those reported by other researchers, were utilized to check the validity of the proposed model. According to the outcomes, the model could predict the cracking severity of the tested concretes with a relative precision.

  • 7.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mats, Emborg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Estimation of specific surface area of particles based on size distribution curve2018In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, no 10, p. 533-540Article in journal (Refereed)
    Abstract [en]

    Workability in the fresh state is one of the most important factors in design and production of concrete and can be related to the water demand of the mixture, which in addition to other factors is a function of the particle shape of aggregates and binders and their specific surface area. While it is known that the shape of fine particles has a significant effect on the water demand, there are uncertainties regarding how the various shape parameters would affect the specific surface area, mainly because up to now many of the shape parameters have not yet been clearly defined and there are no commonly accepted methods for their measurement and/or estimation. In this research, the actual particle shapes were replaced with regular convex polyhedrons to calculate the total specific surface area using the size distribution curves of the samples. The obtained results indicate that while, in some cases, the assumption of a spherical particle shape leads to an acceptable estimation of the specific surface area when compared with Blaine test results, the specific surface area of powders with more angular particles could be calculated more accurately with the assumption of a polyhedron shape rather than a sphere.

  • 8.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A method for obtaining optimum packing of aggregates for concrete at the onset of flow2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017, p. 361-365Conference paper (Refereed)
    Abstract [en]

    Particle packing models have been studied extensively during past decades and led to development of some complex and relatively accurate predictions of packing of granular materials. While the models are capable of calculating the packing density for different volumetric share of constitutes, the concept of optimum packing remains unclear. The study aims to define optimum packing based on particle packing theory and excess water layer theory .The approach makes it also possible to calculate amount of paste that is required to put a concrete mixture at the onset of flow. Some pilot tests conducted in the laboratory showed good agreement with calculated data.

  • 9.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Effect of Water-Cement Ratio on Plastic Shrinkage Cracking in Self-Compacting Concrete2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference 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.

  • 10.
    Persson, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Silfwerbrand, Johan
    Department of Civil and Architectural Engineering Department of Structural and Architectual Engineering Division, Royal Institute of Technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Interface stresses in concrete bridge deck overlays subjected to differentialshrinkage2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper (Refereed)
    Abstract [en]

    Concrete overlays on bridge decks are expected to be more durable as compared with the more common asphalt solution. Besides stresses due to traffic load and temperature variations at service, the overlays are exposed to stresses due to long term shrinkage. Of interest is to evaluate the concrete overlay due to the shrinkage induced stresses at the composite interface. Three strategies have been employed to gain knowledge on the stresses; 1) use of non-destructive test systems via field observations, 2) a numerical study on a concrete composite slab tested in laboratory, 3) recordings of realistic shrinkage and climate data on a reference bridge using vibrating strain gauges and humidity probes in the newly cast concrete overlay. The data were used as input data for a linear elastic finite element model. This article demonstrates this last phase of the work.

  • 11.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Betongindustri AB, Stockholm.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Skanska Sverige AB, Gothenburg.
    Plastic Shrinkage Cracking in Concrete: Influence of Test Methods2017Conference paper (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.

  • 12.
    Hösthagen, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. anders.hosthagen@ltu.se.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Thermal Crack Risk Estimations of Concrete Walls: Temperature and Strain Measurements Correlated to the Equivalent Restraint Method2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper (Refereed)
    Abstract [en]

     Self-induced non-elastic deformations in hardening concrete, caused by restrained volume changes due to thermal dilatation and moisture deformations, often leads to cracking. In crack risk analyses, determination of the degree of restraint is vital. One model to estimate the restraint and calculate the thermal crack risk is the Equivalent Restraint Method, ERM. The method has previously been analyzed but needs to be further examined and validated. Recordings of tunnel sections were performed and compared to calculated values by ERM. Satisfying correlation between theoretically estimated and observed temperatures, strains and time of through cracking was achieve which is promising for future implementation and testing of the method.

  • 13.
    Nilimaa, Jonny
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hösthagen, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Thermal Crack Risk of Concrete Structures: Evaluation of Theoretical Models for Tunnels and Bridges2017In: Nordic Concrete Research, ISSN 0800-6377, Vol. 56, no 1, p. 55-69Article in journal (Refereed)
    Abstract [en]

    An approach for thermal crack risk estimations was introduced in the Swedish design guidelines BRO 94. The cracking occurs during the early hardening process because of the exothermic reactions between water and cement and often result in high repair costs and delayed construction. This paper studies and validates the inherent safety levels for one typical case of concrete structure. Three slab-frame structures were analysed and the original crack risk estimations were compared to the actual cracking and postcalculations were carried out, using actual parameters. This paper shows that walls with computed strain ratios over 70% were affected by thermal cracks.

  • 14.
    Nilimaa, Jonny
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hösthagen, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Validation of the Swedish Crack Risk Estimation Models2017In: Proceedings of the 23rd Nordic Concrete Research Symposium: Aalborg, Denmark, 21 - 23 August 2017, Oslo: Nordic Concrete Federation , 2017, p. 321-324Conference paper (Refereed)
    Abstract [en]

    Thermal cracking may occur during the early hardening process of concrete as a result of the exothermic reactions between water and cement. An approach for thermal crack risk estimation and prevention was introduced in the Swedish design guidelines BRO 94. This paper studies and validates the current safety levels existing concrete structures. Three slab-frame structures were analysed and the preliminary crack risk estimations were compared to the actual cracking and post-estimations were carried out, using actual parameters. This paper shows that all the studied walls with a strain ratio over 70% were affected by thermal cracks.

  • 15.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elsa och Sven Thysells Stiftelse för konstruktionsteknisk forskning inom väg och vatten vid Luleå tekniska universitet: En skrift tillägnad Donator Sven Thysell på 100-årsdagen 2016-09-022016Report (Other (popular science, discussion, etc.))
    Abstract [sv]

    Denna skrift ger en kort beskrivning av Elsa och Sven Thysells stiftelse för konstruktionsteknisk forskning inom väg- och vatten vid Luleå tekniska universitet. Skriften har sammanställts inför donator Sven Thysells 100-årsdag den 2 september 2016. Vi är mycket tacksamma för det stöd Stiftelsen har gett och ger till konstruktionsteknisk forskning vid LTU. Stödet betyder mycket för att vår verksamhet skall kunna utvecklas till nytta för samhället

  • 16.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Löfgren, Ingemar
    Chalmers University of Technology.
    PLASTIC SHRINKAGE CRAKING IN SELF-COMPACTING CONCRETE: A PARAMETRIC STUDY2016In: 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 (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.

  • 17.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Quantification of the shape of particles for calculating specific surface area of powders2016In: RILEM publication S.A.R.L, Denmark, 2016, Vol. 115, p. 31-41Conference paper (Refereed)
    Abstract [en]

    The concepts of particle packing and water/paste layer theory are commonly used for basis of concrete mix design models. While particle packing insists on achieving fewer voids in aggregate matrix by adding fine aggregate, water/paste layer theories state that increasing the amount of fines will lead to higher water demand since the specific surface area of particles will increase. In order to calculate the thickness of excess paste, it is essential to quantify the shape of particles. However, there are uncertainties regarding how the various shape parameters would affect the packing and specific surface, mainly because up to now many of the shape parameters are not yet clearly defined and there are no commonly accepted methods for their measurement. In addition, the term “shape” needs to be defined, some research suggest that for obtaining an appropriate shape factor several parameters need to be measured e.g. flakiness, elongation, sphericity, convexity etc. The paper aims to derive a shape factor based on variation of packing from the packing of ideal spheres with the same particle size distribution as the studied aggregate and to apply the shape factor to calculate an approximate specific surface area value.

  • 18.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Enochsson, Ola
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lundmark, Tore
    Ramböll Sverige AB, Luleå.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Protecting a five span prestressed bridge against ground deformations2015In: IABSE Conference Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges, Geneva: International Association for Bridge and Structural Engineering, 2015, p. 255-262Conference paper (Other academic)
    Abstract [en]

    A 55 year-old, 121.5 m long, five span prestressed bridge was situated in the deformation zone close to a mine in Kiruna in northern Sweden. There was a risk for uneven ground deformations so the bridge was analyzed and monitored. Results and measures taken to ascertain the robustness of the bridge are presented.The analysis resulted in an estimate that the bridge could sustain 24 mm in uneven horizontal and 83 mm in uneven vertical displacement of the two supports of a span. To be able to sustain larger deformations, the columns of the bridge were provided with joints, where shims could be inserted to counteract the settlements. To accomplish this, each one of the 18 columns of the bridge was unloaded by help of provisional steel supports. The column was then cut and a new foot was mounted to it. This made it possible to lift each individual column with two jacks, when needed, and to adjust its height by inserting or taking away shim plates.The deformations of the bridge and the surrounding ground were monitored. The eigenmodes of the bridge were studied with accelerometers and by analysis with finite elements (FE) models. Comparison indicated good agreement between the model and the actual bridge, with calculated eigenfrequencies of 2.17, 4.15 and 4.67 Hz, for the first transversal, vertical and torsional modes, respectively. Measurements during winter resulted in higher values due to increased stiffness caused by frozen materials.

  • 19. Carlswärd, Jonas
    et al.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Avoiding undesirable end results of bonded steel fibre concrete overlays: observations from tests and theoretical calculations2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 49, p. 93-112Article in journal (Refereed)
    Abstract [en]

    Due to a high degree of damages and undesirable final results of bonded overlays, research has been conducted to develop recommendations on design and execution. Laboratory and half scale tests as well as theoretical analyses have been carried out including e. g. base and end restraint tests on overlays with various reinforcement, concrete qualities, substrate preparing and curing. Also, analytical and numerical calculations have been performed. Results reveal that the bond between overlay and substrate is the most critical parameter for a successful final result. Other key parameters are shrinkage and curing, while fibre and bar reinforcement generally proved to be less significant. Theoretical models work well on this case and will be further developed

  • 20.
    Persson, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bridge deck concrete overlays: full scale studies2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 49, p. 163-180Article in journal (Refereed)
    Abstract [en]

    Concrete overlays on bridge decks are thought to be more durable when comparing with the more common solution with asphalt. Of interest is to evaluate the concrete overlay regarding traffic and shrinkage/temperature induced stresses. In a pilot study nondestructive test systems were evaluated with focus on detecting hidden defects, (e.g. debonding), that may have induced identified surface cracks. Furthermore, calibration of material parameters for a similar composite slab was done using finite element technique and compared with experimental studies in laboratory. Good agreement was found between numerical and experimental results. This will serve as an input for future bridge FE-models.

  • 21.
    Persson, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bridge deck concrete overlays: full scale studies and theoretical analysis2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 509-512Article in journal (Refereed)
    Abstract [en]

    Concrete overlays on bridge decks are thought to be more durable when comparing with the more common solution with asphalt. Of interest is to evaluate the concrete overlay regarding traffic and shrinkage/temperature induced stresses. In a pilot study nondestructive test systems were evaluated with focus on detecting hidden defects, (e.g. debonding), that may have induced identified surface cracks. Furthermore, calibration of material parameters for a similar composite slab was done using finite element technique and compared with experimental studies in laboratory. Good agreement was found between numerical and experimental results. This will serve as an input for future bridge FE-models.

  • 22.
    Gram, Hans-erik
    et al.
    Cementa AB.
    Westerholm, Mikael
    Cementa AB.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Crushed fine aggregate for concrete production2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 113-117Article in journal (Refereed)
  • 23.
    Hösthagen, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Equivalent Restraint Method Correlated to Empirical Measurements2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 505-508Article in journal (Refereed)
    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.

  • 24.
    Orosz, Katalin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fjellström, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Evaluation of the Linear Logarithmic Creep Model2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 417-420Article in journal (Refereed)
    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.

  • 25.
    Orosz, Katalin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fjellström, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Evaluation of Thermal Dilation and Autogenous Shrinkage at Sealed Conditions2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 299-302Article in journal (Refereed)
    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.

  • 26.
    Jonasson, Jan-Erik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Measurement and modelling of strength and heat of hydration for young concrete2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 501-504Article in journal (Refereed)
    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.

  • 27.
    Johansson, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Methods to optimize aggregate composition: evaluation by concrete experiments2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 201-204Article in journal (Refereed)
    Abstract [en]

    A proper mix design optimizes the environmental impact and the cost effectiveness of a concrete. A minimum cement paste content is desirable without deteriorate the concrete properties. Thus, cement paste content is dependent on the packing properties of the aggregates. Three different methods to optimize the aggregate composition have been evaluated by concrete tests: one curve fitting method and two particle packing methods. Crushed and natural aggregates have been tested at two different w/c ratios. The results show that the methods suggest very different aggregate compositions and they can´t handle fine crushed aggregates that consume a lot of mixing water.

  • 28.
    Johansson, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Methods to Optimize Aggregate Distribution: Evaluation by Concrete and Mortar Experiments2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, p. 145-157Article in journal (Refereed)
    Abstract [en]

    A proper mix design optimizes the environmental impact and the cost effectiveness of a concrete. A minimum cement paste content is desirable without deteriorate the concrete properties. The cement paste content is dependent on the packing properties of the aggregates and it of interest to estimate the packing correctly. Three methods to optimize the aggregate distribution have been evaluated by concrete tests for crushed and natural aggregates: one curve fitting method and two particle packing methods. It is shown that the methods suggest very different aggregate distributions for an optimum concrete mix and they can´t handle fine crushed aggregate that consumeings a lot of mixing water.

  • 29.
    Jonasson, Jan-Erik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Lars-Olof
    Lunds tekniska högskola, LTH.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Moisture and mechanical properties aimed for crack risk analyses if early age concrete2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 409-412Article in journal (Refereed)
    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

  • 30.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Particle Packing for Concrete Mix Design: Models vs. Reality2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, p. 85-94Article in journal (Refereed)
    Abstract [en]

    The packing density of aggregates is of great importance in concrete mix design as obtaining a higher packing density leads to less usage of cement paste which has technical, environmental and economic benefits. It is thus of interest to model particle packing correctly. Hence, in this study, packing densities of seven mixes of aggregate were attained in the laboratory using the loose packing method and were compared to values suggested by three models: 4C, Compressible Packing Model and Modified Toufar Model. Modified Toufar showed 1.72% mean difference from the laboratory values while CPM and 4C had mean differences of 1.79% and 1.84% respectively. In addition, it was found that some of the models are preferable in certain mixtures.

  • 31.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Plastic Shrinkage Cracking in Concrete: State of the Art2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, p. 95-110Article in journal (Refereed)
    Abstract [en]

    As plastic shrinkage cracking can dramatically reduce the durability of a concrete member and causes considerable repair costs annually, a comprehensive understanding of the mechanism of the phenomenon is essential to prevent these damages in future. In this paper, an overview is given on the mechanism of plastic shrinkage crack formation and the status of present technologies avoiding the cracking are reported through referring to previously conducted research and observations.

  • 32.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Plastic shrinkage cracking: research in Scandinavia2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 351-354Article in journal (Refereed)
    Abstract [en]

    As plastic shrinkage cracking still causes considerable repair costs annually, an understanding of the phenomenon is essential to prevent these damages in the future. In the paper, the status of present technology to avoid cracking is briefly reported through referring to research conducted in Scandinavia. In addition, on-going activities at LTU are described and future plan is demonstrated. Thus, experiments are performed on concrete slabs cast in rectangular moulds and cured at some variations of environmental conditions. The results will be used to find critical evaporation rate at very early age.

  • 33.
    Ronin, Vladimir
    et al.
    EMC Development AB.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Self-Healing Performance and Microstructure Aspects of Concrete Using Energetically Modified Cement with a High Volume of Pozzolans2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, p. 131-144Article in journal (Refereed)
    Abstract [en]

    Self-healing can increase the lifetime and durability of concrete structures. The self-healing properties of concrete made with Energetically Modified Cement (EMC), which has a pozzolan content of up to 70%, have been investigated. In such concretes, pozzolanic reactions within the cement cause the gradual formation of fresh C-S-H gel, which seals cracks as they form. The self-healing of small EMC concrete samples was tested in a laboratory, and field observations of an EMC concrete highway pavement were made. The EMC concrete exhibited fewer cracks than conventional concrete, and was observed to self-heal cracks with widths of up to 0.2 mm.

  • 34. Carlswärd, Jonas
    et al.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Shrinkage cracking of thin concrete overlays2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 355-359Article in journal (Refereed)
    Abstract [en]

    Due to a high degree of damages and undesirable end results of bonded overlays, research is conducted to develop recommendations on design and execution. Laboratory and full scale tests as well as theoretical analyses have been carried out including e. g. base and end restraint tests on overlays with various reinforcement, concrete qualities, substrate preparing and curing. Moreover, analytical and numerical calculations have been performed. Results reveal that the e. g. bond between overlay and substrate is a critical parameter for a successful end result. Another key parameter is sufficient curing, while reinforcement generally proved to be less significant. Theoretical models works well on this structural situation and will be further developed.

  • 35.
    Hösthagen, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wallin, Kjell
    Projektengagemang i Stockholm AB.
    Stelmarcik, Marcin
    Thermal crack risk estimations for tunnel: equivalent restraint method correlated to empirical observations2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 49, p. 127-143Article in journal (Refereed)
    Abstract [en]

    The present study deals with the correlation between numerical models and empirical observations in newly cast concrete structures. The model used is the equivalent restraint method, ERM, which is established from several local restraint method calculations, LRM. The casting of walls and roof in a tunnel construction is investigated. Correlation between models and empirical measurements is established in three steps: 1) the restraint situation is analyzed; 2) the calculated temperature developments are compared to empirical temperature measurements to calibrate the models; and 3) calculated strain ratios are compared with observed crack patterns, and in general a good correlation is achieved

  • 36.
    Fjellström, Peter
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heat loss compensation for semi-adiabatic calorimetric tests2013In: Nordic Concrete Research, ISSN 0800-6377, Vol. 47, no 1, p. 39-60Article in journal (Refereed)
    Abstract [en]

    Heat of hydration has long been of importance since it affects the temperature levels within a concrete structure, and thus, potentially affects its durability. The only source of energy is the reaction between cement and water. This energy warms up the concrete sample and all the ambient materials. Therefore, in order to model these energies, the TSA (traditional semi-adiabat) setup is transformed into an associated sphere. By this, the temperature distribution and the energies within each layer of the TSA can be calculated. The sum of all energies gives the total heat of hydration. A refined model using a correction factor is introduced, which accounts for energies lost to the TSA setup materials. Results show that the effect of this factor cannot be disregarded, especially not for TSAs with low cooling factors.

  • 37.
    Hatem, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Pusch, Roland
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Pourbakhtiar, Alireza
    Proportioning of cement-based grout for sealing fractured rock-use of packing models2013In: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 5, no 10, p. 765-774Article in journal (Refereed)
    Abstract [en]

    Fractured, very permeable rock hosting repositories for radioactive waste will require grouting. New grout types of possible use where long-term performance is needed should have a small amount of cement for minimizing the increase in porosity that will follow from the ultimate dissolution and erosion of this component. They have to be low-viscous and gain strength early after injection and packing theory can assist designers in selecting suitable proportions of various grout components. Optimum particle packing means that the porosity is at minimum and that the amount of cement paste needed to fill the voids between aggregate particles is very small. Low porosity and microstructural stability must be guaranteed for long periods of time. Organic additives for reaching high fluidity cannot be used since they can give off colloids that carry released radionuclides and talc can be an alternative superplasticizer. Low-pH cement reacts with talc to give high strength with time while Portland cement gives early but limited strengthening. The clay mineral palygorskite can be used for early gelation because of its thixotropic properties. Once forced into the rock fractures or channels in soil it stiffens and serves as a filter that prevents fine particles to migrate through it be lost. However, its hydrophilic potential is too high to give the grout a high density and high strength. According to the experiments carried out most of the investigated grouts are injectable in fractures with apertures down to 100 μm.

  • 38.
    Hatem, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Pusch, Roland
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Alireza, Pourbakhtiar
    Talc-based concrete for sealing borehole optimized by using particle packing theory2013In: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 7, no 4, p. 440-455Article in journal (Refereed)
    Abstract [en]

    The paper describes assessment of the performance of cement-poor concreteson the basis of packing theory. The concretes are intended for sealing segments of deep boreholes and have a small amount of cement for minimizing the mutual chemical impact on the contacting clay seals. The composition is examined by application of packing theory with respect to the cement/aggregate ratio and the gradation of the aggregate material which is crushed quartzite for providing high internal friction after maturation, as well as to talc added for fluidity and to the small amount of cement. Low porosity and micro-structural stability must be guaranteed for very long periods of time. The study exemplifies how packing theory assist designers in selecting optimal proportions of the various components. Optimum particle packing implies minimizing the porosity and thereby reducing the amount of cement paste needed to fill the voids between the aggregate particles. The use of talc as inorganic super-plasticizer since ordinary organic additives for reaching high fluidity at casting are undesirable, and since talc reacts with cement and provides high strength in along-term perspective.

  • 39.
    Nilsson, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fastenings (anchor bolts) in concrete structures: influence of surface reinforcement2012In: Concrete Structures for Sustainable Community: proceedings of the International FIB Symposium 2012, Stockholm, Sweden, 11 - 14 June 2012 / [ed] Dirch H. Bager; Johan Silfwerbrand, Stockholm: Swedish Concrete Association , 2012, p. 419-422Conference paper (Refereed)
    Abstract [en]

    Tests have been carried out to study the influence of surface reinforcement on the load bearing capacity of cast-in headed bars. In 66 tests, rods with a diameter of Φ30 mm and a Φ45 mm nut at the end, were cast-in place centrically in concrete slabs. Width, length and thickness of the slabs varied from 1.2 m × 1.2 m × 0.3 m up to 2.2 m × 2.2 m × 0.6 m. The top reinforcement varied from 0% to about 1.2% (Φ 16 #100). A considerable increase in the load-bearing capacity was noted. The increase depends on the geometry and the amount and placement of the reinforcement. A numerical model to evaluate the influence is proposed.

  • 40.
    Fjellström, Peter
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Model for concrete strength development including strength reduction at elevated temperatures2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 45, no 1, p. 25-44Article in journal (Refereed)
    Abstract [en]

    When casting concrete structures, one of the most important properties is the concrete strength development. The need of actions on site is different at various stages of hardening, from the fresh concrete to the hardened concrete. The paper defines a model analysing maturity and associated strength growth within three important time periods. The model can be applied separately within each of these periods depending on test data available.It is shown in the paper that the temperature plays an important role on the strength development of concrete structures. The hydration rate increases with increased temperatures, which can be described by maturity functions. If the concrete temperature remains high, strength reduction at later ages usually occurs compared to hardening at lower temperature, which may be denoted strength reduction at elevated temperatures or cross over effects. Both these phenomena have been implemented in the model for strength growth presented in the paper. The functionality of the model is demonstrated by evaluation of laboratory tests for five concrete mixes and two types of cement.

  • 41.
    Hatem, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Pusch, Roland
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Packing theory for natural and crushed aggregate to obtain the best mix of aggregate: research and development2012In: Proceedings of World Academy of Science, Engineering and Technology, ISSN 2010-376X, E-ISSN 2070-3740, Vol. 67, p. 819-825Article in journal (Refereed)
    Abstract [en]

    Concrete performance is strongly affected by the particle packing degree since it determines the distribution of the cementitious component and the interaction of mineral particles. By using packing theory designers will be able to select optimal aggregate materials for preparing concrete with low cement content, which is beneficial from the point of cost. Optimum particle packing implies minimizing porosity and thereby reducing the amount of cement paste needed to fill the voids between the aggregate particles, taking also the rheology of the concrete into consideration. For reaching good fluidity superplasticizers are required. The results from pilot tests at Luleå University of Technology (LTU) show various forms of the proposed theoretical models, and the empirical approach taken in the study seems to provide a safer basis for developing new, improved packing models.

  • 42.
    Sandström, Thomas
    et al.
    WSP Group.
    Fridh, Katja
    Division of Building Materials, Lund University.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hassanzadeh, Manouchehr
    Vattenfall Research & Development.
    The influence of temperature on water absorption in concrete during freezing2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 45, no 1, p. 45-58Article in journal (Refereed)
  • 43.
    Larsson, Johan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    A study of the future for concrete bridge construction in Sweden2011In: Nordic Concrete Research: Proceedings of the XXI Nordic Concrete Symposium, Hämeenlinna, Finland 2011, Oslo: The Nordic Concrete Federation , 2011, p. 533-536Conference paper (Refereed)
  • 44.
    Sas, Gabriel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Enochsson, Ola
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Puurula, Arto
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Flexural-shear failure of a full scale tested RC bridge strengthened with NSM CFRP: Shear capacity analysis2011In: Nordic Concrete Research, ISSN 0800-6377, Vol. 2/2011, no 44, p. 189-206Article in journal (Refereed)
  • 45. Enochsson, Ola
    et al.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Gruvvägsbron I Kiruna: Deformationskapacitet2011Report (Other academic)
    Abstract [sv]

    En bedömning har gjorts av hur stora deformationer Gruvvägsbron i Kiruna kan klara med bibehållen bärförmåga. I projektet har mätningar av brons beteende vid statisk och dynamisk belastning utförts under vinter- respektive sommarförhållanden. Mätningarna har utvärderats och analyserats med FEMprogram för att kunna bedöma brons styvhet och deformationskapacitet. Syftet har varit att undersöka hur mycket bron klarar av i stödförändringar på grund av gruvdriften. Preliminära gränsvärden för stödförändringar har tagits fram.Brons statiska funktionssätt är tillfredsställande. Enligt hittillsvarande mätningar (t o m dec 2010) har endast små markrörelser ägt rum vilket inte nämnvärt påverkar brons funktion.Brons dynamiska funktionssätt är också tillfredsställande. Uppmätta egenmoder och egenfrekvenser är normala för denna typ av förspänd balkbro. Bron är förhållandevis styv och de analytiska och numeriska beräkningar(FEM-analyser) som gjorts tyder på att den har förhållandevis begränsad deformationskapacitet. Vi bedömer att bron klarar följande lokala deformationsskillnad mellan två närliggande pelare: (a) i horisontalled ca 40mm och (b) i vertikalled ca 80 mm. Om tillåtna värden sätts till hälften av de möjliga erhålls:Tillåten differens för rörelse(a) i tvärled mellan en pelares över- och underkant till = ca 20 mm(b) i höjdled mellan två intilliggande stöd till = ca 40 mmVärdena kan komma att revideras (förfinas) i samband med att resultat blir tillgängliga från fortsatta mätningar och observationer av brons beteende.Några markrörelser av betydelse inträffade inte mellan november 2006 och 2008, men under 2009 och 2010 har rörelser skett med några mm. Brons längdändring på grund av temperaturvariationer är dock betydligt större. Bronär ca 3 – 4 cm längre på sommaren än på vintern. Eftersom markrörelserna förväntas bli betydligt större i samband med att gruvans brytningsfront närmar sig bron försågs brons pelare under sommaren2010 med en anordning rdning så att deras läge kan justeras om markrörelserna blirojämna.

  • 46.
    Simonsson, Peter
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Increasing the use and performance of SCC in bridges2011In: Nordic Concrete Research: Proceedings of the XXI Nordic Concrete Research Symposium, Hämeenlinna, Finland 2011, Oslo: The Nordic Concrete Federation , 2011, p. 99-103Conference paper (Refereed)
  • 47.
    Simonsson, Peter
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Robust self compacting concrete for bridge construction2011In: Nordic Concrete Research, ISSN 0800-6377, Vol. 2011, no 44Article in journal (Refereed)
  • 48.
    Emborg, Mats
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simonsson, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Increasing the market share of SCC2010In: Concrete Plant International, ISSN 1437-9023, no 3, p. 218-222Article in journal (Other academic)
  • 49.
    Carlswärd, Jonas
    et al.
    Betongindustri AB.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Prediction of stress development and cracking in steel fiber-reinforced self-compacting concrete overlays due to restrained shrinkage2010In: Fiber-Reinforced Self-Consolidating Concrete: Research and Applications, American Concrete Institute, 2010, p. 31-49Conference paper (Refereed)
    Abstract [en]

    Shrinkage cracking of self-compacting concrete (SCC) overlays with and without steel fibres has been assessed through laboratory testing and theoretical analysis. Test results verified that steel fibre reinforcement has a crack width limiting effect. However, the contribution in case of fibre contents up to 0.75 vol% was not found to be sufficient to distribute cracks in situations where bond to the substrate was nonexistent. Thus, even higher steel fibre contents (or other types of fibres) are required in order to control cracks. A distributed pattern of fine cracks was however obtained even for unreinforced SCC within bonded areas of the overlays. This implies that steel fibres, or other crack reinforcement, are not required if high bond strength is obtained. An analytical model, proposed to assess the risk of cracking and to predict crack widths in overlays, was found to give reasonable correlation with experimental results

  • 50.
    Emborg, Mats
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carlswärd, Jonas
    Hedin, Christer
    Jonasson, Jan-Erik
    Program kortar ner väntetid när betonggolv ska glättas2010In: Husbyggaren : bygg, el, VVS, anläggning, ISSN 0018-7968, no 2Article in journal (Other (popular science, discussion, etc.))
123 1 - 50 of 130
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