Abstract Municipal solid waste incineration (MSWI) residues such as fly ash and air pollution con... more Abstract Municipal solid waste incineration (MSWI) residues such as fly ash and air pollution control (APC) residues may serve as new supplementary cementitious materials (SCM). These SCMs may, however, require a pre-treatment to improve material properties. This study investigates the impact of electrodialytically remediated (EDR) MSWI residues to remove heavy metals and salts, on the phase development, setting, and compressive strength development of composite cements with 10 wt% cement replacement, compared to inert quartz or untreated (raw) MSWI residues. All treated MSWI residues showed reactivity in mortar, resulting in higher compressive strength than inert quartz, attributed to additional ettringite and monocarbonate formation. The results indicate that electrodialytical remediation improves the performance of MSWI fly ash in blends with Portland cement, while MSWI APC residues might be used without pre-treatment.
The environmental impact during concrete manufacturing can be reduced by using less cement or usi... more The environmental impact during concrete manufacturing can be reduced by using less cement or using types of cement with high amounts of secondary cementitious materials (SCMs) and fillers. Fly ash from municipal solid waste incineration (MSWI) is an unused material, which could potentially be used as an SCM or filler. The applicability of MSWI fly ash samples in cement-based materials was investigated through an indirect determination based on the chemical composition, toxic metal content and particle size distribution of the samples. Furthermore, how the samples compared to each other and how representative the samples were for MSWI fly ash, in general, were investigated by multivariate modelling. MSWI fly ash samples were obtained from Denmark, Sweden and Greenland. Comparing the chemical composition of the MSWI fly ash samples with the chemical requirements for coal fly ash to be used in concrete, specified in EN 450-1 2012, indicated a low potential as SCMs. Additionally, the MSWI fly ash contained and leached more toxic metals than the allowed limits. The particle size distributions were larger than cement and indicated limited potential as filler. A principal component analysis showed that the obtained samples were chemically different materials compared to each other and would have different effects if used in cement-based materials. Additionally, the samples from Denmark were unrepresentative of MSWI fly ash, while the Greenlandic and Swedish samples were comparable to previously studied MSWI fly ash samples.
Abstract: The method of mixing may affect the degree of agglomeration of particles in cement-base... more Abstract: The method of mixing may affect the degree of agglomeration of particles in cement-based materials and thus the properties of the materials in their fresh, hardening, and hardened state. Paste (w/c=0.35) of white Portland cement with and without 10% silica fume and 0.65% superplasticizer were mixed by hand and in a high-speed mixer. Chemical shrinkage was measured to illustrate the effect of mixing on development of hydration. Chloride migration was measured on 28 days old pastes to illustrate the effect of mixing on the hydrated ...
Fibre orientation and volume distribution affect the post-cracking tensile strength, which is one... more Fibre orientation and volume distribution affect the post-cracking tensile strength, which is one of the main design parameters of fibre-reinforced concrete (FRC). This paper discusses the influence of unidirectional and grid reinforcement on fibre orientation and distribution in FRC slabs. Slabs without conventional reinforcing bars were used as a reference. The slab size was 1200 x 1200 x 150 mm. Numerical simulations were used to predict the fibre orientation and X-ray computed tomography (CT) to determine the actual fibre orientation and distribution. Beams were sawn from each slab, CT-scanned and tested in three-point bending tests in accordance with EN 14651. Both the numerical simulations and the CT results show that the rebars caused a more isotropic fibre orientation in the lower halves of the slabs. This was confirmed in the bending tests, where the lowest variation and highest residual tensile strengths were documented for beams sawn from slabs with grid reinforcement. Fibre migration from the upper layer to middle and lower layers of the slabs due to gravity was observed in all slabs, and in the reinforced slabs, migration also depended on the distance from the casting point. The reinforcement led to an accumulation of fibres above the rebars in the middle layer of each reinforced slab. A set of mechanisms is proposed to explain the experimental results.
A comparison of the water distribution in the different systems, based on computer inodeling and ... more A comparison of the water distribution in the different systems, based on computer inodeling and direct observation of two-dimensional cross sections, is given.
This thesis is submitted as a partial fulfilment of the requirements for the Danish Ph.d. degree.... more This thesis is submitted as a partial fulfilment of the requirements for the Danish Ph.d. degree. The thesis is divided into two parts. The first part introduces motivation and aim of the research. Furthermore, the main findings and conclusions of the research are presented here. The second part is a collection of five papers, reporting the research in more detail. iii Dr. Robert J. Flatt (SIKA technology, Switzerland) for his many invaluable inputs, suggestions and comments to the project. All the people at YKI who assisted and helped me during my research stay, in particular Ph.d. Annika Kauppi (now at Sandvik Tooling, Sweden). The project has benefitted greatly from results from the EC-financed research project "Design and function of novel polymeric admixtures for more durable high performance concrete". In this connection, the partners of the project are thanked for their readiness to help with providing materials and sharing information.
To benefit from the full potential of fluid concretes such as Self-Compacting Concrete (SCC) tool... more To benefit from the full potential of fluid concretes such as Self-Compacting Concrete (SCC) tools for prediction of the form filling of SCC are needed. Such tools should take into account the properties of the concrete, the shape and size of the structural element, the position of rebars, and the casting technique. The present lack of such tools may lead to selection of highly flowable mixes with tendency to segregate or mixes without high static and dynamic stability, increasing the risk of improper form filling. Although substantial progress has been made in the field of fluid concretes, we must not forget that the most suitable concrete to cast a given element is a concrete which is just sufficiently fluid to fill the formwork. Additional and thus unnecessary fluidity will always have a cost, e.g. in terms of increased super-plasticizer amount, increased porosity causing loss of mechanical resistance and durability and increased risk of segregation. Important requirements to the hardened concrete are total form filling and bond to reinforcement, homogeneity with regard to paste composition, aggregate distribution and air void content, and high quality surfaces without surface air voids ("blowholes"). All these aspects condition the future hardened properties of the material. Segregation could increase the local porosity and thus the permeability of the concrete to aggressive substances. Varying content of cement paste causes heterogeneous shrinkage and creep in a given concrete element. Moreover, high heterogeneity will increase the probability that these time-dependent phenomenon yield high internal stress gradients and thus cracking. Computational modeling of flow could be used for simulation of e.g. total form filling and detailed flow behavior as particle migration and formation of granular arches between reinforcement ("blocking"). But computational modeling of flow could also be a potential tool for understanding the rheological behaviour of concrete and a tool for mix proportioning. Progresses in the correlation between mix proportioning and rheological parameters would of course result but, moreover, the entire approach to mix proportioning could be improved. Indeed, just as numerical simulations of the loading of concrete structures allow a civil engineer to identify a minimum needed mechanical strength, numerical simulation of the casting process could allow the same engineer to specify a minimum workability of the fresh concrete that could ensure the proper filling of a given formwork. This paper describes the present status regarding computational modeling of the flow of fresh concrete. Fresh concrete is a suspension of particles in a matrix. Depending on the purpose of the simulation and behavior of the concrete the scales at which the solid components of the concrete
A comparison of the water distribution in the different systems, based on computer inodeling and ... more A comparison of the water distribution in the different systems, based on computer inodeling and direct observation of two-dimensional cross sections, is given.
The orientation of steel fibres affects the flexural performance of fibre-reinforced concrete. In... more The orientation of steel fibres affects the flexural performance of fibre-reinforced concrete. In this paper, selected experimental methods for the characterization of fibre orientation are evaluated and the relationship between residual flexural tensile strength and fibre orientation is discussed. To illustrate the applicability of the methods, the impact of the formwork surface on fibre orientation in slabs cast with fibre-reinforced self-compacting concrete (slump-flow class SF1 according to EN206) was investigated for the cases of formwork surfaces with slip, semi-slip and rough condition. The comparison of fibre orientation quantification methods showed good agreement between X-ray computed tomography and image analysis of sections from sawn beams. The variation in fibre orientation over the slab thickness was strongly influenced by the flow and the roughness of the formwork surface. The Thorenfeldt model for the impact of the fibre orientation factor on residual flexural tensile strength (used in the Norwegian proposal for fibre concrete guidelines) was verified and showed good agreement. Keywords Fibre orientation Á X-ray computed tomography (CT) Á Image analysis Á Residual flexural tensile strength Á Fibre-reinforced concrete G. Ž irgulis (&) Á E.
Abstract Municipal solid waste incineration (MSWI) residues such as fly ash and air pollution con... more Abstract Municipal solid waste incineration (MSWI) residues such as fly ash and air pollution control (APC) residues may serve as new supplementary cementitious materials (SCM). These SCMs may, however, require a pre-treatment to improve material properties. This study investigates the impact of electrodialytically remediated (EDR) MSWI residues to remove heavy metals and salts, on the phase development, setting, and compressive strength development of composite cements with 10 wt% cement replacement, compared to inert quartz or untreated (raw) MSWI residues. All treated MSWI residues showed reactivity in mortar, resulting in higher compressive strength than inert quartz, attributed to additional ettringite and monocarbonate formation. The results indicate that electrodialytical remediation improves the performance of MSWI fly ash in blends with Portland cement, while MSWI APC residues might be used without pre-treatment.
The environmental impact during concrete manufacturing can be reduced by using less cement or usi... more The environmental impact during concrete manufacturing can be reduced by using less cement or using types of cement with high amounts of secondary cementitious materials (SCMs) and fillers. Fly ash from municipal solid waste incineration (MSWI) is an unused material, which could potentially be used as an SCM or filler. The applicability of MSWI fly ash samples in cement-based materials was investigated through an indirect determination based on the chemical composition, toxic metal content and particle size distribution of the samples. Furthermore, how the samples compared to each other and how representative the samples were for MSWI fly ash, in general, were investigated by multivariate modelling. MSWI fly ash samples were obtained from Denmark, Sweden and Greenland. Comparing the chemical composition of the MSWI fly ash samples with the chemical requirements for coal fly ash to be used in concrete, specified in EN 450-1 2012, indicated a low potential as SCMs. Additionally, the MSWI fly ash contained and leached more toxic metals than the allowed limits. The particle size distributions were larger than cement and indicated limited potential as filler. A principal component analysis showed that the obtained samples were chemically different materials compared to each other and would have different effects if used in cement-based materials. Additionally, the samples from Denmark were unrepresentative of MSWI fly ash, while the Greenlandic and Swedish samples were comparable to previously studied MSWI fly ash samples.
Abstract: The method of mixing may affect the degree of agglomeration of particles in cement-base... more Abstract: The method of mixing may affect the degree of agglomeration of particles in cement-based materials and thus the properties of the materials in their fresh, hardening, and hardened state. Paste (w/c=0.35) of white Portland cement with and without 10% silica fume and 0.65% superplasticizer were mixed by hand and in a high-speed mixer. Chemical shrinkage was measured to illustrate the effect of mixing on development of hydration. Chloride migration was measured on 28 days old pastes to illustrate the effect of mixing on the hydrated ...
Fibre orientation and volume distribution affect the post-cracking tensile strength, which is one... more Fibre orientation and volume distribution affect the post-cracking tensile strength, which is one of the main design parameters of fibre-reinforced concrete (FRC). This paper discusses the influence of unidirectional and grid reinforcement on fibre orientation and distribution in FRC slabs. Slabs without conventional reinforcing bars were used as a reference. The slab size was 1200 x 1200 x 150 mm. Numerical simulations were used to predict the fibre orientation and X-ray computed tomography (CT) to determine the actual fibre orientation and distribution. Beams were sawn from each slab, CT-scanned and tested in three-point bending tests in accordance with EN 14651. Both the numerical simulations and the CT results show that the rebars caused a more isotropic fibre orientation in the lower halves of the slabs. This was confirmed in the bending tests, where the lowest variation and highest residual tensile strengths were documented for beams sawn from slabs with grid reinforcement. Fibre migration from the upper layer to middle and lower layers of the slabs due to gravity was observed in all slabs, and in the reinforced slabs, migration also depended on the distance from the casting point. The reinforcement led to an accumulation of fibres above the rebars in the middle layer of each reinforced slab. A set of mechanisms is proposed to explain the experimental results.
A comparison of the water distribution in the different systems, based on computer inodeling and ... more A comparison of the water distribution in the different systems, based on computer inodeling and direct observation of two-dimensional cross sections, is given.
This thesis is submitted as a partial fulfilment of the requirements for the Danish Ph.d. degree.... more This thesis is submitted as a partial fulfilment of the requirements for the Danish Ph.d. degree. The thesis is divided into two parts. The first part introduces motivation and aim of the research. Furthermore, the main findings and conclusions of the research are presented here. The second part is a collection of five papers, reporting the research in more detail. iii Dr. Robert J. Flatt (SIKA technology, Switzerland) for his many invaluable inputs, suggestions and comments to the project. All the people at YKI who assisted and helped me during my research stay, in particular Ph.d. Annika Kauppi (now at Sandvik Tooling, Sweden). The project has benefitted greatly from results from the EC-financed research project "Design and function of novel polymeric admixtures for more durable high performance concrete". In this connection, the partners of the project are thanked for their readiness to help with providing materials and sharing information.
To benefit from the full potential of fluid concretes such as Self-Compacting Concrete (SCC) tool... more To benefit from the full potential of fluid concretes such as Self-Compacting Concrete (SCC) tools for prediction of the form filling of SCC are needed. Such tools should take into account the properties of the concrete, the shape and size of the structural element, the position of rebars, and the casting technique. The present lack of such tools may lead to selection of highly flowable mixes with tendency to segregate or mixes without high static and dynamic stability, increasing the risk of improper form filling. Although substantial progress has been made in the field of fluid concretes, we must not forget that the most suitable concrete to cast a given element is a concrete which is just sufficiently fluid to fill the formwork. Additional and thus unnecessary fluidity will always have a cost, e.g. in terms of increased super-plasticizer amount, increased porosity causing loss of mechanical resistance and durability and increased risk of segregation. Important requirements to the hardened concrete are total form filling and bond to reinforcement, homogeneity with regard to paste composition, aggregate distribution and air void content, and high quality surfaces without surface air voids ("blowholes"). All these aspects condition the future hardened properties of the material. Segregation could increase the local porosity and thus the permeability of the concrete to aggressive substances. Varying content of cement paste causes heterogeneous shrinkage and creep in a given concrete element. Moreover, high heterogeneity will increase the probability that these time-dependent phenomenon yield high internal stress gradients and thus cracking. Computational modeling of flow could be used for simulation of e.g. total form filling and detailed flow behavior as particle migration and formation of granular arches between reinforcement ("blocking"). But computational modeling of flow could also be a potential tool for understanding the rheological behaviour of concrete and a tool for mix proportioning. Progresses in the correlation between mix proportioning and rheological parameters would of course result but, moreover, the entire approach to mix proportioning could be improved. Indeed, just as numerical simulations of the loading of concrete structures allow a civil engineer to identify a minimum needed mechanical strength, numerical simulation of the casting process could allow the same engineer to specify a minimum workability of the fresh concrete that could ensure the proper filling of a given formwork. This paper describes the present status regarding computational modeling of the flow of fresh concrete. Fresh concrete is a suspension of particles in a matrix. Depending on the purpose of the simulation and behavior of the concrete the scales at which the solid components of the concrete
A comparison of the water distribution in the different systems, based on computer inodeling and ... more A comparison of the water distribution in the different systems, based on computer inodeling and direct observation of two-dimensional cross sections, is given.
The orientation of steel fibres affects the flexural performance of fibre-reinforced concrete. In... more The orientation of steel fibres affects the flexural performance of fibre-reinforced concrete. In this paper, selected experimental methods for the characterization of fibre orientation are evaluated and the relationship between residual flexural tensile strength and fibre orientation is discussed. To illustrate the applicability of the methods, the impact of the formwork surface on fibre orientation in slabs cast with fibre-reinforced self-compacting concrete (slump-flow class SF1 according to EN206) was investigated for the cases of formwork surfaces with slip, semi-slip and rough condition. The comparison of fibre orientation quantification methods showed good agreement between X-ray computed tomography and image analysis of sections from sawn beams. The variation in fibre orientation over the slab thickness was strongly influenced by the flow and the roughness of the formwork surface. The Thorenfeldt model for the impact of the fibre orientation factor on residual flexural tensile strength (used in the Norwegian proposal for fibre concrete guidelines) was verified and showed good agreement. Keywords Fibre orientation Á X-ray computed tomography (CT) Á Image analysis Á Residual flexural tensile strength Á Fibre-reinforced concrete G. Ž irgulis (&) Á E.
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