| 1. |
- Al-Ayish, Nadia, et al.
(författare)
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Environmental impact of concrete structures reinforced with GFRP bars : A simplified study on columns
- 2019
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Ingår i: Proceedings of the fib Symposium 2019. - : International Federation for Structural Concrete. - 9782940643004 ; , s. 1998-2005
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Konferensbidrag (refereegranskat)abstract
- Concrete has a significant influence on the global warming due to its high usage in the construction industry. There are a few different strategies to increase the sustainability potential of concrete structures. Most of these strategies involve reduction of the total clinker content. One strategy, which is often neglected due to its complexity, is to increase the durability of the concrete structure. By increasing the durability, the need for repair and maintenance is reduced and thus less resources are consumed during the service life. One of the main deterioration mechanisms in concrete structures is the corrosion of steel reinforcement. A strategy to increase the service life of concrete structures in harsh environment would therefore be to increase the durability of concrete or to use low- or non-corrosive reinforcement instead of traditional steel reinforcement. This paper focuses on the latter. Glass fibre reinforced polymer (GFRP) bars are non-corrosive and have emerged as an alternative to steel bars in reinforced concrete structures in harsh environment. They have other mechanical properties than steel and opens for alternative mix designs for concrete. However, the environmental impact of concrete structures reinforced with GFRP bars has not been fully investigated and most life-cycle assessment (LCA) studies have an exchange ratio of 1:1 between GFRP and steel bars despite differences in the mechanical properties. This paper studies the climate impact of concrete columns reinforced with GFRP bars through an LCA methodology, focusing on the functional unit.
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| 2. |
- Al-Ayish, Nadia
(författare)
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Environmental Impact of Concrete Structures - with Focus on Durability and Resource Efficiency
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Concrete is essential for the construction industry with characteristic properties that make it irreplaceable in some aspects. However, due to the large volumes consumed and the energy intense cement clinker production it also has a notable climate impact. In order to reach the international and national sustainability goals it is therefore important to reduce the climate impact of concrete structures.There are many ways to influence the environmental impact of concrete and a detailed analysis is one of the actions that could push the industry and the society towards a sustainable development. The purpose of this research is to evaluate the environmental impact of concrete structures and the built environment and to highlight the possibilities to reduce that impact with choice of concrete mix and innovative design solutions.A life cycle assessment (LCA) was carried out to analyze the environmental impact of two thin façade solutions with innovative materials and to evaluate influences of different greenhouse gas reducing measures on concrete bridges. The influence of supplementary cementitious materials (SCM) in terms of climate impact and durability was also analyzed.The results indicate that SCMs have a twofold effect on the climate impact of reinforced concrete structures. Not only do they reduce the greenhouse gases through cement clinker replacement but also by an improvement of durability regarding chloride ingress. Currently, this is not considered in the regulations, which makes it difficult to foresee in LCA at early design stages. The results also show great possibilities to reduce the climate impact through different measures and design alternatives and the need for further development of products and solutions.
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| 3. |
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| 4. |
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| 5. |
- Al-Ayish, Nadia, et al.
(författare)
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The influence of supplementary cementitious materials on climate impact of concrete bridges exposed to chlorides
- 2018
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 188, s. 391-398
-
Tidskriftsartikel (refereegranskat)abstract
- In order to reach a specific service life of reinforced concrete structures a certain cover thickness is needed. At present, this is regulated by national standards that also limit the amount and type of supplementary cementitious materials in different exposure environments. The regulations do not, however, consider the actual durability performance of concrete with supplementary cementitious materials. As a consequence, the LCA results might be misleading. This paper shows the environmental impact of concrete with supplementary cementitious materials in chloride environment considering their specific performances. Prescriptive and performance based service life prediction models for chloride ingress are applied and compared.
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| 6. |
- Blanksvärd, Thomas, et al.
(författare)
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Textile reinforced concrete sandwich panels
- 2011
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Ingår i: Nordic Concrete Research. - Oslo : Norsk Betongforening. - 9788282080255 ; , s. 517-520
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Konferensbidrag (refereegranskat)
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| 7. |
- Dalenbäck, Jan-Olof, 1954, et al.
(författare)
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Ställ tekniska egenskapskrav och använd deklarationerna
- 2014
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Ingår i: Energi & Miljö. - 1101-0568. ; 2014:4, s. 40-41
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Ta bort energikraven i BBR och ersätt dem med ändamålsenliga egenskaps¬krav. Gör sedan energideklarationerna värda namnet genom att inkludera hushålls- och verk¬sam¬hets¬el så att de kan användas för att följa upp energi¬användningen. I anslutning till Boverkets regeringsuppdrag (N2014/75/E) att definiera nya energihus¬håll¬ningskrav, finns det all anledning att diskutera om vi är på rätt väg med de krav på bygg¬naders energi¬prestanda som ställs i Boverkets Byggregler (BBR). Speciellt om dess uppfyllelse ska vara juridiskt bindande.
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| 8. |
- During, Otto, et al.
(författare)
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Life cycle cost analysis on impregnated bridge edge beams
- 2014
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Ingår i: Restoration of Buildings and Monuments. - 1864-7251. ; 20:6, s. 441–446-
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Tidskriftsartikel (refereegranskat)abstract
- the edge beams. However, results from this study pointed out that in most cases there is a clear economic benefit to impregnate the bridge edge beams even if it has to be repeated every 15 years.
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| 9. |
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| 10. |
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| 11. |
- Flansbjer, Mathias, et al.
(författare)
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Textile reinforced concrete sandwich panels
- 2012
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Ingår i: fib Symposium 2012: Concrete Structures for Sustainable Community - Proceedings. - Stockholm : Swedish Conrete Association. - 9789198009811 ; , s. 169-172
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Konferensbidrag (refereegranskat)abstract
- The main reason for the thickness of a concrete sandwich element is the requirement for the protective concrete cover for the steel reinforcement. By changing the steel reinforcement to non-corrosive textile fibre net this requirement could be strongly reduced. Use of textile reinforced concrete (TRC) makes it possible to produce much thinner and slimmer concrete facades in the future without changing their mechanical properties. This article presents selected results from Tekocrete project (Formas-BIC) concerning pilot production, modelling and full-scale testing of new light weight sandwich elements reinforced with AR glass and carbon fibre nets.
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| 12. |
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| 13. |
- Helsing, Elisabeth, et al.
(författare)
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A Nordic method for testing hydrophobic impregnations with regard to prevention of chloride ingress
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Chloride induced corrosion of the reinforcement is the major cause of degradation of reinforced concrete structures. In particular in the Nordic countries, the use of de-icing salts during winter, leads to severe degradation of edge beams in road bridges. Thus, in order to extend the service life and decrease maintenance costs, hydrophobic impregnations are commonly used to prevent or slow down chloride ingress into concrete. There is a harmonised European standard for hydrophobic impregnations, EN 1504-2 [1], but the property “diffusion of chloride ions” is “subject to national standards and regulations”. The transport and road administrations of Sweden, Norway and Finland use different national methods to evaluate the performance of this type of products meaning that the same CEmarked product needs to meet different requirements. Therefore, the transport and road administrations of Sweden, Norway and Finland initiated a project with the aim to establish a common Nordic method for classification of hydrophobic impregnations with regard to their capability to protect concrete from chloride ingress. The project was divided into three phases consisting on the analysis of existing test standards (national and international), a pre-study to evaluate the influence of different tests parameters and a round robin test involving three laboratories (one in each country). A thorough comparison of the existing methods and review of relevant literature made it possible to define which test parameters could be used in the formulation of the new method and which ones required further studies. It was found that the type of surface to be treated, the length of the preconditioning period, the length of the curing period and whether the surface to be impregnated should be soaked with Ca(OH)2-solution or not should be further investigated. The results of the pre-study showed that the application of the impregnation to form surfaces led to somewhat better chloride blocking effect. Despite this, it was decided to use sawn surfaces in the method, since it is much easier to obtain reproducible surface characteristics that way. The characteristics of a form surface depend on e.g. the form material, use of release agents, curing conditions. Saturation of the surface with calcium hydroxide solution before impregnation was found slightly beneficial on the chloride blocking effect compared to when such a treatment was omitted. However, since this did not contribute to the robustness of the test results, it increased the number of experimental steps and it is not representative of practice in real structures, it was decided not to incorporate such a treatment in the new method. The chloride protection slightly increases with the impregnation curing time. It was not clear which factor was most dominant; if the continuous polymerization of the hydrophobic impregnation or the continuous cement hydration. Since enough curing time is necessary for the treatment to be efficient, it was decided that the curing period before exposure to chlorides should be 28 days. With the primary objective of determining the reliability and reproducibility of the new method, a round robin exercise was carried out. Three laboratories were involved in this phase; CBI-Borås in Sweden, SINTEF in Norway and VTT in Finland. The results show that despite some differences in both materials and methods, such as the type of cement or preconditioning and curing environments, highly reproducible results were obtained. In addition, a detailed discussion on the influence of the details of the method on the chloride profiles and on the filter effect is presented. Within the round robin test, the relative humidity before and after impregnation and the dry condition of the powder samples were found to be the major parameters leading to the discrepancy of the results. In addition, handling of the wet concrete surfaces after exposure to chlorides and the time period (and temperature) between the end of the chloride exposure and powder sampling for chloride analysis were found to have surprisingly large effects on the form of the chloride profiles in the samples. Therefore, these parts of the procedures were made much more precise in the final method, in order to increase its reproducibility. The method can be briefly described as follows: Concrete specimens are prepared by sawing 100 mm cubes into two halves, three cubes per test series. The sawn surfaces are defined as exposure faces. Three halves are treated with the hydrophobic impregnation to be tested and the other three halves are kept as untreated references. The specimens are exposed submerged in 15% NaCl-solution for 56 days. After exposure, the chloride ingress is determined by profile grinding and the total amount of penetrated chlorides is calculated. The chloride blocking effect of the hydrophobic impregnations, expressed as the Filter Effect, FE, which is determined as 1 minus the ratio between the amount of penetrated chlorides in treated and in non-treated concrete specimens. The results obtained in both the pre-study and round robin exercise were compared to those obtained with the existing national methods in order to establish proper requirement levels with the new method. Despite the many differences between the methods, it was found that a filter effect of approximately 0.65 correlates well with the existing requirement in the Swedish method and in the Norwegian method. However, given limited data available and also considering data from field investigations, a level of 0.60 is proposed as appropriate for a really well performing hydrophobic impregnation. The method was accepted as a Nordtest method in December 2015 with the denomination NT Build 515.
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| 14. |
- Helsing, Elisabeth, et al.
(författare)
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Kortversion av SVU-rapport 2022:5 ”Klimatförbättrad betong för dricksvattenanläggningar”
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This RISE report is a short version of SVU report 2022:5 “Klimatförbättrad betong för dricksvattenanläggningar” (Low carbon concrete for drinking water infrastructure). The purpose of the project was to clarify if the carbon footprint of concrete for drinking water infrastructure can be lowered by replacing Portland cement with supplementary cementitious materials (SCM) accepted for use in concrete without influencing the quality of the drinking water negatively with regard to trace substances and PAH. In addition to reviewing the literature, leaching tests and LCA analyses were conducted on thirteen concretes mixes with varying binder compositions. The results show that it is possible to replace up to 50 % of the cement with the SCMs, ground granulated blast furnace slag (GGBS), silica fume and fly ash. All this may be GGBS and up to 35 % fly ash may be used. This is valid under condition that a drinking water facility which in its entirety is new drinking goes through a tuning period of some days up to a week during which the water quality is monitored before water is delivered to clients. Leaching of some substances is somewhat increased and others are decreased by the replacement of the cement, however the changes are so small that the content in the drinking water in a real facility is only marginally influenced. Which type of binder to use should be decided based on other these materials influence on other concrete properties, for instance on the strength development. The decrease of the carbon footprint is roughly proportional to the cement replacement ratio.
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| 15. |
- Helsing, Elisabeth, et al.
(författare)
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Vidareutveckling av provningsmetod för klotterskyddsprodukter för betongytor
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Further development of a test method for anti-graffiti products for concrete surfaces Modified test methods for the performance of anti-graffiti coatings are presented in this report. As a base a test method applied in Sweden since is used which involves outdoor exposure of concrete slabs on which the coatings are applied followed by application of the graffiti and cleaning. The modifications are based on a review of methods existing in other countries, discussions with producers of anti-graffiti coatings and a test program carried out at RISE in Borås. The tests were carried out with two sacrificial coatings and some permanent coatings. In the latter case the graffiti is applied and cleaned ten times. In the existing method, the outdoor exposure is said to be three months. However, it was found that when this exposure takes place, in winter or in summer, greatly influenced the protective capability of the coating. In this project the influence of three different exposures were investigated; three month summer exposure, three month winter exposure and twelve month exposure. The test showed that the three-month summer exposure and the twelve-month exposure gave comparable results. Hence prolonging the exposure period is not necessary. However, very deviating results were obtained after the three-month winter exposure. The evaluation of the protective capability is started with a visual inspection against certain specified assessment criteria on remaining stains and visible marks of graffiti. If the coating met the assessment criteria for the visual inspection, assessment criteria on colour changes measured with a colour measuring device shall also be met. Separate assessment criteria for measured colour changes are used for sacrificial and for permanent anti-graffiti coatings. For a sacrificial coating, the assessment criterium is given in relation to the original concrete surface, while for a permanent coating the assessment criterium is formulated in relation to the exposed surface. It was found that the performance requirement on changes in gloss was irrelevant. In the revised method the selection of colour types and water temperature and pressure used in pressure washing has been modified to be consistent with praxis. The drying between cycles including application of graffiti and cleaning was shortened. The method is divided into two methods; one for sacrificial anti-graffiti coatings and one for permanent anti-graffiti coatings that does not require the use of chemical compounds. The latter method is not applicable to permanent anti-graffiti coatings which need the help of chemical products to give satisfactory cleaning.
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| 16. |
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| 17. |
- Lindqvist, Jan-Erik, et al.
(författare)
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Assessment of mechanical durability properties of rock materials using quantitative microscopy and image analysis
- 2003
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Rapport (refereegranskat)abstract
- This report presents a project that focuses on the assessment of mechanical durability properties using quantitative microscopy. The project was financed by SGU under grant 03-1174/98. The aim has been to develop methods for assessment and presentation of rock quality data. Both optical and SEM/BSE microscopy were applied and combined with computerised image analysis and manual methods for the quantitative analysis. The first part of the project was to produce a literature overview of image analysis as applied to rock materials. A method for assessment of resistance to fragmentation of granitic rocks comparable with the Los Angeles test has been developed. By means of a quantitative description of foliation using a foliation index, FIX, it is possible to assess the potential length-thickness ratio of the crushed aggregate. Methods developed in the main part of the project have been applied in related areas. These include crack initiation and propagation under cyclic loading and cyclic thermal stress.
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| 18. |
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| 19. |
- Malaga, Katarina, et al.
(författare)
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Alkali Resistance of Textile Reinforcement for Concrete Façade Panels
- 2014
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Ingår i: XXII NORDIC CONCRETE RESEARCH SYMPOSIUM.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Textile reinforced concrete has been proven to be a suitable solution for the production of thin and lightweight façade panels. Despite it being researched over the past decade, its long-term durability is not sufficiently characterized. This article presents experimental results from accelerated aging and direct tensile testing of various textile reinforcement alternatives according to ISO 10406-1. Based on the results, a large degeneration of the glass and basalt fibre bars was observed after 30 days of immersion. As for carbon fibre grids, no significant difference in ultimate tensile force was noted before and after immersion.
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| 20. |
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| 21. |
- Malaga, Katarina
(författare)
-
Blick för forskning
- 2014
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Ingår i: Cementa. - 0346-8771. ; :2, s. 16-19
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 22. |
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| 23. |
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| 24. |
- Malaga, Katarina
(författare)
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Consolidation of Gotland sandstone
- 2004
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Ingår i: 10th International Congress on Deterioration and Conservation of Stone.
-
Konferensbidrag (refereegranskat)
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| 25. |
- Malaga, Katarina
(författare)
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Effekten av impregnering och klotterskydd är oklar
- 2009
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Ingår i: Husbyggaren. - 0018-7968. ; 51:5, s. 36-38
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Klotter kostar runt en miljard årligen. Ett problem är att det saknas testmetoder för att avgöra om ett klotterskydd är effektivt mot klotter och smuts på en viss typ av yta. Inom kulturvård används impregnering för att förstärka byggnadsmaterial.
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| 26. |
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| 27. |
- Malaga, Katarina, et al.
(författare)
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Field exposure sites and accelerated laboratory test of marble panels
- 2004
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Ingår i: Proceedings of the international conference on Dimension Stone 2004, 14-17 June 2004, Prague, Czech Republic. - : Taylor & Francis Group plc, A.A Balkema Publishers.
-
Konferensbidrag (refereegranskat)abstract
- The use of thin marble and limestone for facade cladding has increased substantially during the last five decades. The durability of thin slabs (often only 30 mm thick) has been assumed to be satisfactory based on centuries of successful use as a structural building stone. Nevertheless, all over the world, the long-term deformation and strength loss of some claddings have led to concerns about its safe and durable use. The detailed assessment of marble and limestone within TEAM (see also www.sp.se/building/team) is used to develop a hypothesis for the observed deterioration and to develop remedial actions. This paper describes the field exposure sites, the accelerated test, and presents parts of the results. The results indicates that all marbles bow, but at different magnitudes. The marbles demonstrate diurnal and seasonal variation in bowing and dependence on the thickness and impregnation. The final evaluation of the results will be presented in 2005.
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| 28. |
- Malaga, Katarina, et al.
(författare)
-
Kartläggning av befintlig provningsverksamhet för cement och betong i Sverige och bedömning av provningsbehov vid introduktion av nya cement
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten presenterar resultat från projektet ‘Kartläggning av befintlig provnings-verksamhet för cement och betong i Sverige och bedömning av provningsbehov vid introduktion av nya cement’. Mot bakgrund av en minskad eller stoppad produktion av cement vid Cementas fabrik i Slite gav Regeringen Verket för innovationssystem (VINNOVA) den 3 november 2021 i uppdrag att kartlägga befintlig provningsverksamhet för cement och betong (N2021/02773) som finns tillgänglig för svenska aktörer och att föreslå åtgärder som kan skapa förutsättningar för en samordning vid en kraftigt ökad efterfrågan på denna verksamhet. Denna rapport behandlar hur provningsbehovet kan komma att utvecklas vid stopp i den svenska cementproduktionen i Slite vilket resulterar i ett behov av introduktion av stora volymer av ett eller flera nya cement under kort tid. Denna händelse benämns i rapporten förenklat som “cementkris”. Rapporten pekar på några förutsättningar som bör gälla för att ett cementbyte skall kunna genomföras rimligt kontrollerat. I rapporten görs det inte någon bedömning av hur byggbranschen eller samhället i stort skulle påverkas av en cementkris. Det görs inte heller någon analys av vem som tillser att produktions-bortfallet från Slite ersätts med annat cement eller varifrån detta cement kan komma. För en bedömning av provningsbehovet av betong har detta inte någon avgörande betydelse. Ett nytt cement från Kina kräver för betongtillverkaren lika mycket provning som ett nytt cement från närområdet i Europa eller för den delen Sverige. Förutsatt att cementet i sig är CE-märkt och uppfyller svenska krav.Den huvudsakliga slutsatsen är att: Under förutsättning att inte avkall får göras på de krav som ställs på cement och betong i Sverige idag krävs det att nu använda och nya cement finns tillgängliga parallellt under en övergångsperiod på minst två och ett halvt år. Detta gäller främst betong till anläggningskonstruktioner och infrastrukturprojekt där kraven på kvalitetssäkring via provning på ackrediterade laboratorier är hög. På grund av ökat provningsbehov går det inte att genomföra ett omfattande byte av cement på ett stort antal betongfabriker under kort tid utan betydande störningar och stopp i betongleveranser till svenska byggarbetsplatser, om inte nu använda och nya cement finns tillgängliga parallellt. Inom husbyggnadsområdet är behoven av provning på ackrediterade laboratorier lägre. Hur snabbt och smidigt ett byte av cement kan göras för husbyggnadsbetong avgörs i stället av möjligheterna att utföra nödvändiga interna provningar och intrimningar på fabrikerna.Om nu använda och nya cement till anläggningsbyggandet finns tillgängliga parallellt under minst två och ett halvt år är bedömningen att nödvändig ökning av provnings-kapacitet hinner byggas upp samtidigt som ett byte från nu använda till nya cement kan göras på ett rimligt kontrollerat sätt med avseende på behovet av extern provning. Detta förutsätter emellertid att samtliga nya cement är CE-märkta och uppfyller svenska krav samt en samordning av provningskapaciteten inom vissa kritiska provnings-områden. För att öka provningskapaciteten på nationell nivå inom kritiska provnings-områden krävs en noggrann planering av hur en sådan utökning skall genomföras (lokaler, utrustning, kompetens, vem som skall vara huvudman) och vem som skall bekosta en sådan ökning av provningskapaciteten.
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Malaga, Katarina
(författare)
-
Ny fasad med textilarmering
- 2012
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Ingår i: Cementa. - 0346-8771. ; :2
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 35. |
- Malaga, Katarina
(författare)
-
Ny VD
- 2014
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Ingår i: Svensk Bergs & Brukstidning. - 0039-6435. ; 93:1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 36. |
- Malaga, Katarina, et al.
(författare)
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Relevance of hydrophobic and oleophobic properties of antigraffiti systems on their cleaning efficiency on concrete and stone surfaces
- 2013
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Ingår i: Journal of materials in civil engineering. - 0899-1561 .- 1943-5533. ; 25:6, s. 755-762
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of graffiti is not entirely restricted to urban areas, but also appears frequently in rural communities and along traffic infrastructure. Besides its aesthetic and societal effects, graffiti cause considerable removal costs and subsequent costs for repairing damages caused by improper graffiti removal. Over the last two decades, strategies have been developed to combat graffiti in the built environment, including the development of protective measures in the form of antigraffiti systems (AGSs). Antigraffiti systems promise to be affordable and easily applicable for a wide range of substrates, and many products have already been on the market for many years. In practice, however, successful application of AGS and removal of graffiti depend on many factors in which the type of coating and condition of the substrate play critical roles. The optimal environmental goal is to use AGS without any cleaning chemicals except for pure water. Available studies on the behavior of the same AGS on various substrates can show completely different results concerning the cleaning efficacy and the durability of the AGS under different climatic conditions. The question of which properties of an AGS are most essential for its efficiency has still not been fully investigated. The goal of this study was to investigate cleaning efficacy in conjunction with hydrophobic and oleophobic properties of the AGS on different substrates. The results showed that hydrophobicity and oleophobicity are important for dense substrates but have a low influence on porous substrates. In this case, cleaning efficiency is majorly determined by the physical properties of the substrates.
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| 37. |
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| 38. |
- Malaga, Katarina, et al.
(författare)
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Tekniska textilier i betong
- 2010
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Ingår i: CBI-nytt. - 0349-2060. ; :2, s. 2-3
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 39. |
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| 40. |
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| 41. |
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| 42. |
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| 43. |
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| 44. |
- Malaga-Starzec, Katarina, et al.
(författare)
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Efflorescence on thin sections of calcareous stones
- 2004
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Ingår i: Journal of Cultural Heritage. - : Elsevier BV. - 1296-2074. ; 4:4, s. 313-318
-
Tidskriftsartikel (refereegranskat)abstract
- Limestone and marble, still frequently used as building materials are especially vulnerable to the destructive effects of efflorescence. The effect of interaction between five different calcareous stones and corrosive atmospheres has been investigated. A novel technique of stone degradation analysis has been used where thin sections of fresh stone materials were exposed in a corrosion chamber under controlled conditions (temperature, relative humidity (RH), SO2 and NO2 concentration). Following 1-weeks exposure; observations of the initial crystallisation were studied by light microscopy, scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The results obtained from the surface analysis clearly showed sulphation of the samples and formation of gypsum. Observations of the initial corrosion indicated differences in the location of efflorescence and its shape among and within the samples. The mineralogy, grain shape and size, mineral defects and existence of cracks and pores, all influenced the substrates reactivity. The most vulnerable areas and the places where the corrosion started on the calcitic stones were the triple grain junctions followed by grain boundaries, and on the dolomitic marble cracks and pores.
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| 45. |
- Malaga-Starzec, Katarina, et al.
(författare)
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Model study of initial adsorption of SO2 on calcite and dolomite
- 2004
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 222:1-4, s. 82-88
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Tidskriftsartikel (refereegranskat)abstract
- The rate of calcareous stone degradation is to a significant extent controlled by their surface chemistry with SO2. Initial surface sulphite is converted to a harmful gypsum upon, e.g. NO2 catalysed oxidation. However, it has been observed by scanning electron microscopy that the lateral distributions of gypsum crystals differ between calcitic and dolomitic marbles. The first-principles density functional theory is employed to understand the origin of these fundamentally different morphologies. Here, the stability differences of surface sulphite at calcite CaCO3 (s) and dolomite CaxMg1-xCO3 (s) are determined. A qualitative difference in surface sulphite stability, favouring the former, is reported. This is taken to imply that calcitic microcrystals embedded in a dolomitic matrix act as sinks in the surface sulphation process, controlled by SO2 diffusion. The subsequent formation of gypsum under such conditions will not require SO42+ (aq) ion transport. This explains the homogeneous distribution of gypsum observed on the calcitic micro-crystals in dolomite. In contrast, sulphation on purely calcitic marbles never reaches such high SO2 Coverage. Rather, upon oxidation, SO42+ (aq) transport to nucleation centres, such as grain boundaries, is required for the growth of gypsum crystals.
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| 46. |
- Mueller, Urs, et al.
(författare)
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Development of pore structure and hydrate phases of binder pastes blended with slag, fly ash and metakaolin – A comparison
- 2015
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Ingår i: ICCC 2015 Beijing.
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Konferensbidrag (refereegranskat)abstract
- Blended binder systems in concrete have been in use for many years. However, over the recent discussions on the sustainability of cement and concrete the topic became of paramount importance for the construction industry. In Sweden blended binder systems in concrete were applied fairly recently and supplementary cementitious materials (SCM) were not used largely before. In Sweden over the last 30 years engineering structures were built, with exceptions, with a low alkali, sulfate resistant Portland cement due to domestic requirements. Therefore, in context to blended binder systems durability is a major point being discussed. Most interest lays in the resistance towards frost, carbonation and chloride penetration and the experience with blended systems was limited. It is therefore the goal of this study to investigate blended binder systems over a longer hydration period of up to two years in context to durability. The results presented here will focus on the porosity and hydrate phase development within the first 90 days of hydration. In this study in total 9 different binder blends were studied. The blends included different replacement levels with granulated blast furnace slag from a Swedish producer, fly ash from a Danish power plant and commercially available metakaolin. The matrix included also one set of factory-blended cements (with interground fly ash and slag). The pore structure was investigated by mercury intrusion porosimetry (MIP), phase development by powder x-ray diffraction (XRD). The results are based on the evaluation of binder paste samples. Compared to a reference series consisting of a CEM I the slag containing series showed a continuous decrease of the total pore volume with increasing slag content over 90 days of hydration. The phase development showed a constant increase in monosulfate and hydrotalcite. The amount of these phases increased with increasing slag content. Notable was consumption of C4AF, which increased with the amount of slag and a decrease of C2S reaction. Compared to the reference Portland cement paste the fly ash containing pastes showed increased total pore volumes when the fly ash was just added. For the cement paste with interground fly ash the porosity development was the same as for the reference paste. The phase development for these series showed up to 28 days of hydration formation of ettringite, hemicarbonate and monocarbonate. After 91 days monosulfate was dominating and the amount of hemicarbonate was decreasing. The paste series with 15 % metakaolin showed a strong decrease in total pore volume compared to the reference series within 2 days. Afterwards the pore volume almost leveled to a constant value. The hydration phases included in the beginning large amounts of monosulfate, ettringite and hemicarbonate but changed after 91 days in favor to ettringite and monocarbonate. The metakaolin blend showed the lowest amounts of portlandite in all series, indicating a strong pozzolanic reactivity. The different hydrate phases, in particular AFm phases can help to explain a different behavior towards, e.g. chloride binding. The pore structure development has a large impact not only on strength development but also for ion and moisture transport as well as for carbonation in all series.
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| 47. |
- Mueller, Urs, et al.
(författare)
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Influence of hydrophobicity and oleophobicity on cleaning graffiti on concrete panels and natural stones
- 2012
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Ingår i: Concrete Repair, Rehabilitation and Retrofitting III (ICCRRR). - : TAYLOR and FRANCIS GROUP, LONDON, UK. ; , s. 269-275
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Konferensbidrag (refereegranskat)abstract
- Anti-Graffiti Systems (AGS) are meant to make the cleaning process more efficient by inserting a layer between the paint and the substrate. This layer can have a low surface energy thus make it difficult for the paint to stick to the substrate or it may be easily removed together with the paint. This paper is presenting results from a study of how hydrophobicity and oleophobicity influence the cleaning efficiency of graffiti paints from concrete and natural stones. The results demonstrated that high hydrophobicity and high oleophobicity are not guaranteeing satisfying cleaning effects. The physical properties of a substrate in combination with the characteristics of the AGS layer decide about the cleaning effect.
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| 48. |
- Mueller, Urs, et al.
(författare)
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Novel techniques for studying damage mechanisms of cementitious matrices affected by sulphate attack
- 2012
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Ingår i: fib symposium Concrete Structures for Sustainable Community. ; , s. 267-270
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Konferensbidrag (refereegranskat)abstract
- In the presented study novel methods were applied to analyse the changes of the cement phase composition due to sulphate attack. The analytical methods were based on spatial x-ray diffraction using synchrotron radiation and incoherent white x-ray radiation. The spatial resolution of the methods is ca. 10 μm and 400 μm, respectively. The specimens for phase analysis consisted of thick sections of sulphate exposed cement paste specimen. Different cement pastes showed a clear evolution in the sulphate and phase distribution. Phase analytical data was compared to chemical information acquired by SEM-EDX analysis.
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| 49. |
- Mueller, Urs, et al.
(författare)
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Potential for use of activated clays in concrete in Sweden – Roadmap
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Swedish construction industry is generating a save and affordable built environment for transport, work and living but it is faced with a huge challenge: drastic reduction of greenhouse gases and an increase of circularity in their production cycles. One material, which has inherently embodied CO2, is limestone, which is needed for the production of Portland cement, the essential ingredient in concrete. The CO2 emission during cement production can be drastically compensated by so called supplementary cementitious materials (SCM), which replace cement components causing CO2 emissions. SCM can be used by incorporating them into Portland cement or can be used directly by mixing into concrete. However, traditionally used SCM such as ground granulated blast furnace slag or fly ash are only available in limited amounts in Sweden, not matching the domestic cement production. An alternative to those more traditional SCM is activated or calcined clay, which reacts similar to blast furnace slag or fly ash. Calcined clay is created from natural clays by heating up to 700 ° - 800 °C, where it become very reactive. In this roadmap the state-of-the-art about activated clays is shown from a Swedish perspective. It also shows challenges and needs that have been formulated for a future implementation of activated clays as a component of low carbon concrete.
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| 50. |
- Mueller, Urs, et al.
(författare)
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Reactive powder concrete for facade elements : A sustainable approach
- 2016
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Ingår i: Journal of Facade Design and Engineering. - 2213-302X .- 2213-3038. ; 4:1-2, s. 53-66
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Tidskriftsartikel (refereegranskat)abstract
- Reactive powder concrete (RPC) is a fairly novel material with extraordinary strength and durability properties. Due to these properties, it is increasingly being utilized for external fa¸cade cladding thus enabling a considerable reduction in the thickness of concrete elements. Commercial RPC formulations on the market are usually expensive and less sustainable due to high cement clinker contents. In this study, improved RPC formulations with higher amounts of supplementary cementitious materials (SCMs) were developed. The formulations were combined with different types of reinforcements ranging from steel fibres to fibre textile grids primarily to enhance the ductility and tensile strength of the composite material. The results showed that even with clinker replacement levels of up to ca. 40% of the total binder amount, a satisfactory mechanical performance of the RPC mixes could still be achieved. A fairly steep strength gain rendered heat treatment unnecessary. The materials displayed good flow properties and a reasonably short initial setting time. The incorporation of carbon textile fibre grids proved to be highly effective in improving the post cracking behaviour of the RPC. The results validated a more sustainable approach for RPC applied to thin fa¸cade elements.
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