| 1. |
- Andersson, Patrik, 1974, et al.
(författare)
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Framtidsbilder för samhällsbyggnad
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Framtidsbilder för samhällsbyggnad 2020De kommande 15 åren står institutionen för Bygg- och miljöteknik inför stora förändringar. Därför har institutionen initierat projektet Framtidsbilder 2020 där man engagerat en framtidspanel bestående av elva yngre disputerade forskare. Arbetet inleddes med ett breddgruppsmöte där 110 personer representerande institutionens personal och studenter deltog. Vid mötet identifierades ett antal trender och osäkra utvecklingar som påverkar framtiden inom samhällsbyggnadsområdet. Deltagarna bidrog också med idéer till en önskvärd utveckling, vilket har sammanställts och utgör grunden till en gemensam önskvärd framtid/vision för institutionen. Materialet från breddgruppsmötet har bearbetats av Framtidspanelen och resulterat i fyra scenarier som beskriver hur samhällsbyggnadsområdet kan se ut år 2020. Syftet med framtidsbilderna är att de ska vara vägledande för institutionens beslut och förhållningssätt under de kommande åren.Fyra scenarierTurning TorsoSamhället präglas av en ekonomi som är på uppgång, och av ett nytänkande och öppet samhälle. Materiell status och individualism är viktigt. Detta leder till en hög arbetsbelastning samt krav på exklusiva varor av hög kvali-tet. Det finns en stor medvetenhet om miljöpåverkan och klimatförändringar och lösningarna för att klara energiförsörjningen är innovativa.Eco-metropolenDet sveper en grön våg genom dagens samhälle. Under de senaste 15 åren har vi insett att jorden skall vara en bebolig plats även åt dem som kommer efter oss. Vi söker ständigt efter nya, mer förfinade metoder att tillvarata de resurser vi har. Samhället och individen är i balans. Ekonomin är god och vi är miljömedvetna, trygga och integrerade. Nytänkande premieras och icke- materialistiska värderingar står högt i kurs. Vi tänker individuellt, men agerar mer än gärna för kollektivets bästa. Utbildning är gratis TrädgårdsstadenEtt samhälle där vi lärt oss hantera stress, men känner oss otrygga och helst umgås i slutna sociala sammanhang. Vi bor enkelt inne i stan, eller gärna på landsbygden nära storstäderna. Minskade behov av högutbildade i samhället gör att vi har svårt att rekrytera studenter till teknikutbildningar. Det traditionella tankesättet leder till kulturkrockar med företag och personer från andra länder.Gated communitiesFörsämrad ekonomi och ökad egoism har lett fram till ett stressat, otryggt och segregerat samhälle. Accelererande klimatförändringar och ökad miljö-påverkan skrämmer oss, men trots det åtgärdar vi inte problemen, utan koncentrerar oss på konsekvenserna. Arbetslöshet i samhällsbyggnadssek-torn leder till sänkt status för samhällsbyggaren. Vi har därför svårt att rekrytera studenter, och även forskningen har låg status.
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| 2. |
- Alén, Claes, 1949, et al.
(författare)
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Slitsmurar som permanenta konstruktioner
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Slitsmursteknik är internationellt en vanligt förekommande metod. Den användes framförallt vid djupa schakter för källare och infrastrukturkonstruktioner i innerstadsbebyggelse. Ett annat användningsområde är som tätskärm vid dammar eller deponier. När slitsmuren användes vid djupa schakter utnyttjas den normalt också i den permanenta konstruktionen, vilket ökar metodens ekonomiska konkurrenskraft. Vid tät stadsbyggnad har metoden stora fördelar tack vare sin begränsade omgivningspåverkan (buller, damm, deformationer etc) jämfört med spontslagning och sin goda ekonomi när den kan utnyttjas som permanent konstruktion.I Sverige har slitsmurar använts endast vi ett fåtal tillfällen och då endast som temporär konstruktion. De senaste exemplen är Götatunneln i Göteborg och Citytunneln i Malmö.Med ett ökat undermarksbyggande i våra större städer har intresset ökat för att också utnyttja slitsmuren i den permanenta konstruktionen och därigenom öka den ekonomiska nyttan och även ta mindre mark i anspråk under byggandetI avsikt att utreda möjligheten att kunna acceptera slitsmuren i permanenta konstruktioner tog Vägverket under år 2004 initiativet till ett branschgemensamt utvecklingsprojekt med Vägverket, Banverket och SBUF som finansiärer. Projektet skall resultera i en rekommendation om vilka begränsningar och förändringar som erfordras för att kunna utnyttja tekniken . Alternativt skall projektet utmynna i ett motiverat avstyrkande av tekniken. Behov av ytterligare utvecklingsarbete skall också identifierats.För projektets genomförande har en projektgrupp tillsatts representerande expertis inom de olika områden som är relevanta för slitsmurar. En referensgrupp med representerande för myndigheter, utförare , konsulteroch högskolor har sammankallats vid två tillfällen. Enskilda personer i referengruppen har intervjuats i speciella frågeställningar.Efter inledande litteraturstudier och seminarier i samband med en slitsmurskonferens arrangerad av Vägverket och Banverket har arbetet koncentrerats på följande områden:-Slitsmurens beständighet, framför allt frågeställningar beträffande krav på material ochutförande, konstruktiva lösningar samt sprickviddsbegränsninagr -Geotekniska frågeställningar speciellt med koppling till påverkan på slitsmurens täthet, kvalitet och beständighet.-Inverkan av stödvätska på den färdiga slitsmurskonstruktionens egenskaper -Internationella erfarenheter; brukare och entreprenörer har intervjuats om erfarenheter i driftsskedet och under utförandet. Arbetet och analyser har baserat på litteraturstudier, enkätsvar från beställare och entreprenörer, intervjuer med experter och myndigheter samt egna erfarenheter avslitsmursarbeten inom projektgruppen.För utredning av stödvätskans inverkan på den färdiga slitsmuren har fältförsök utfört vid Citytunnelprojektet i Malmö. Projektgruppen finner att man med dagens kunskaper kan rekommendera slitsmurar för permanent bruk under vissa förutsättningar t.ex:-Betongens vct skall vara mindre än 0,50-Vid konstruktioner med miljöbelastning motsvarande vägmiljö samt vid krav på torr inomhusmiljö bör en inre betongvägg utföras innanför slitsmuren.-Sprickvidden i permanentskedet bör inte överstiga 0,2mm. -Möjlighet finns att åstadkomma frostbeständig betong där så erfordras.-Den tillåtna vidhäftningsspänningen mellan betong och armering reduceras med 20 %. Vissa frågeställningar bör belysas ytterligare för att eventuellt kunna öka potential och ekonomi för permanenta slitsmurar t.ex:-Ett mer nyanserat sätt att formulera sprickviddskrav för att på ett relevant sätt kunna hantera vattentäthet, beständighet och omgivningspåverkan både i permanent- och utförandeskedet.-Vidhäftningens beroende av stödvätskan-Storlek av belastningar som användes vid dimensionering av slitsmurar-Påverkan på betongens hållfasthet och täthet av stödvätska, tillsatsmedel och arbetsutförande.-Påverkan av slitsmurens täthet på omgivningen.Viktiga faktorer för att uppnå ett bra kvalitet på den permanenta slitsmuren är bl.a:-Arbetesutförandet och erfarenheten hos slitsmursentreprenören är av avgörande betydelse för en bra kvalitet.-Samverkan mellan projektör, entreprenör och beställare är viktigt för att uppnå ett bra resultat. -Armeringens utformning och detaljlösningar vid anslutande bjälklag bör ägnas speciell omsorg. För tätt armerade konstruktioner i syfte att uppnå täta konstruktioner kan motverka sitt syfte.-Stödvätskans egenskaper och hantering har en avgörande inverkan på slutproduktens kvalitet.
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| 3. |
- Correia, Vera, et al.
(författare)
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Effect of the addition of GGBS on the frost scaling and chloride migration resistance of concrete
- 2020
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- Ground Granulated Blast-furnace Slag (GGBS) can partially replace cement in concrete to improve certain properties. However, some concerns regarding its performance have been raised. This research aimed at investigating the properties of concrete with GGBS, with special focus on its frost scaling and chloride ingress resistance. Concretes with different amounts of GGBS, different efficiency factors, and different air contents have been tested. The effects of other factors, namely the curing temperature, the use of superplasticizer and carbonation, have also been investigated. The results showed that the frost resistance generally decreases with the increase of the amount of GGBS. However, this research showed that it is possible to produce frost resistant concrete with up to 50% of GGBS by changing some properties of the mix (such as increasing the air content). The results also showed a significant improvement of the chloride ingress resistance for concrete with high additions of GGBS.
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| 4. |
- KNUTSSON, ANNA, 1983, et al.
(författare)
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Freeze/Thaw durability of concrete with fly ash
- 2011
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Ingår i: Nordic Concrete Research. ; Publication No. 43, s. 141-144
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Konferensbidrag (refereegranskat)abstract
- This paper presents results from a study of frost resistance of air entrained concrete with additions of fly ash. In this study, concrete with different additions of fly ash were cured at different ages and elevated temperature prior to the standard frost scaling test. The equivalent water-binder ratio was fixed at 0.45, with efficiency factors of either 0.4 or 1.0. The results show that properly air entrained concrete with fly ash achieved a frost resistance similar or even better than that of Portland cement concrete. Curing for longer ages or at elevated temperature did not improve the freeze/thaw durability.
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| 5. |
- Lindvall, Anders, 1971, et al.
(författare)
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A Procedure for Verification of Models used to predict Chloride Ingress into Concrete
- 2006
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Ingår i: 2nd fib Congress June 5-8, 2006 - Naples, Italy. - 8889972068 ; 2, s. 454-455
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Konferensbidrag (refereegranskat)abstract
- There are several mathematical models available which predict chloride ingress into concrete. A requirement for all these models is that the predictions both have good precision, i.e. have small scatters, and accuracy, i.e. correspond well with measured data. In this paper a procedure to investigate the precision and accuracy of prediction models, used to predict chloride ingress into concrete, is described. The procedure involves determination of the areas, which the measured and predicted profiles, including their scatters, cover in chloride ingress diagrams. The uncertainties in the measured profiles depend on variations in concrete properties, exposure conditions and uncertainties in the measuring techniques, while the uncertainties in the predicted profiles depend on the uncertainties of the input data in the models. The precision of the models is evaluated by studying the areas of the predicted profiles. If the areas are small the precision is good and vice versa. The accuracy of the models can be evaluated by comparing the areas where the measured and predicted profiles are overlapping each other with the total area of the measured and predicted profiles. The quotient between the overlapping and total areas gives a picture of the accuracy where large and small quotients mean good and bad accuracy respectively.Three predictions models are evaluated with the proposed procedure, namely the ClinConc model (physical model), DuraCrete model (empirical model) and the Error-function model (empirical model). The evaluation has been made in four different exposure conditions; marine submerged, splash and atmospheric conditions and along thaw-salted roads. The verification has been made both for short and long term exposure. The results from the verification are combined into success ratios by multiplying them with weight factors. The weight factors are used to show the relevance of each verification, where verifications made in marine submerged conditions and with long term data are considered more relevant than the other verifications. The final results show that the ClinConc model gives both better precision and accuracy compared with the other models. There were large variations in the accuracy between the different exposure conditions, where the best accuracy for all models was achieved in marine submerged conditions. An explanation to this observation is the difficulties to define appropriate boundary conditions in exposure conditions where the concrete is not constantly exposed to seawater.Finally examples are given service life designs made with the evaluated models for concrete exposed in marine submerged and atmospheric conditions. The service life is defined to be ended when reinforcement corrosion is initiated. The predictions have been made with both mean value and pessimistic approaches, where in the latter all influencing parameters are put in such way that a lower limit of the service life is achieved, to illustrate how uncertainties influence service life predictions. The results show that there are significant differences between predictions made with mean value and pessimistic approaches. This is especially the case if the predicted profiles are flat. The predictions made with the empirical models can, however, be questioned since these are made far beyond the data the models are verified against.
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| 6. |
- Lindvall, Anders, 1971
(författare)
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Chloride ingress data from field and laboratory exposure - Influence of salinity and temperature
- 2007
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Ingår i: Cement and Concrete Composites. - : Elsevier BV. - 0958-9465. ; 29:2, s. 88-93
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Tidskriftsartikel (refereegranskat)abstract
- Marine exposure conditions provide an aggressive environment for reinforced concrete structures, mainly due to the occurrence of chloride-induced reinforcement corrosion. There are several influencing factors, but despite a lot of research little is known about the influence from variations in the exposure conditions. Therefore an exposure programme has been made, where concrete specimens, made from one single concrete composition, have been exposed at 12 marine locations around the world, along with a parallel study under laboratory conditions. The specimens have been constantly submerged during the exposure to get well-defined exposure conditions. The purpose was to get a quantitative measure of how different exposure conditions influence the durability of reinforced concrete, measured in terms of chloride ingress into the concrete. The results indicate that the exposure conditions (salinity and temperature of seawater), as expected, influenced the chloride ingress. This is further analysed and discussed in the paper. (c) 2006 Elsevier Ltd. All rights reserved.
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| 7. |
- Lindvall, Anders, 1971
(författare)
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Chloride ingress data from field exposure, at twelve different marine exposure locations, and laboratory exposure
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Concrete specimens, made from one single concrete composition and under identical conditions, have been exposed at different exposure sites around the world. The exposure has mainly been made in marine submerged conditions, i.e. below the surface of the water, to get well-defined exposure conditions. Specimens have also been exposed in marine tidal conditions and along a thaw-salted road. Parallel with the field exposure specimens have been exposed in salt-solutions, with different chloride concentrations and temperatures, in the laboratory. Four or five specimens have been exposed on each site to get a measure of the scatter in chloride ingress. The duration of all exposures has been approximately one year.After finalised exposure the specimens have been analysed for chloride and calcium content (acid-soluble) in depth intervals from the surface. The analyses have been made on dust-samples achieved by means of profile grinding of cores drilled from the specimens. The chloride ingress has been measured as chloride ingress profiles, where the quotient between chloride and binder content is given in depth-intervals. The binder content has been estimated from the analysed calcium content, since the content of acid soluble calcium in the aggregates in the exposed concrete composition is negligible. Additionally chloride-binding isotherms (as free-bound and free-total chloride content) have been determined for the concrete composition used in the exposure programme.The measured chloride ingress profiles have been evaluated with the error-function solution of Ficks second law to derive apparent chloride diffusion coefficients, DF2, and surface chloride contents, Csa. Two additional parameters have been collected to describe non-Fickian behaviour of the profiles, thicknesses of the convection-zones (where the profiles do not fit to the error-function), xc, and surface chloride contents for the diffusion-zones, Csc. Additionally the areas below the chloride ingress profiles have been determined to get an estimate of the amount of chlorides that have penetrated into the concrete.In this report the exposure programme is summarised. The concrete specimens (concrete composition and dimensions) and the exposure locations (geographical locations and exposure conditions) are described. The measurement techniques are briefly described and the results are presented as chloride ingress profiles. Furthermore parameters evaluated from and areas below the profiles are presented. The parameters and areas have also been statistically analysed to get mean values and standard deviations.
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| 8. |
- Lindvall, Anders, 1971
(författare)
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Chloride Ingress in a Swedish Road Environment
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Concrete blocks have been exposed up to five winters at a field station along the motorway Rv40 west of Borås, some 60 km from the Swedish west coast. The concrete mixes are made from a number of Nordic cements and other types of binders (fly ash, silica fume and blast furnace slag) and admixtures. The concrete blocks have been periodically investigated for chloride ingress, frost and salt attack, moisture content and reinforcement corrosion. In this report the chloride ingress measured for three of the exposed concrete mixes, with w/b=0.40 and 0.75 and with an addition of silica fume, is presented. The exposure environment has been documented with data from a meteorological station at the field station together with information about spread of de-icing salt and records of water, snow and ice around the blocks.The chloride ingress is measured as chloride ingress profiles, where the quotient between the chloride and calcium content is given in depth-intervals from the surface. The results show the following:Chloride ingress during a year. There is a build up of chlorides in the concrete during a winter. The build up seems to be more rapid for vertical surfaces but the maximum ingress depths are higher for horizontal surfaces. During the summer there is a redistribution of chlorides, with a transport into the concrete and a decrease of the surface chloride content.Effect of age at the first exposure to chlorides. The age of the concrete at first exposure to chlorides seems to have a decisive effect on the achieved chloride ingress. If the concrete is young at the first exposure to chlorides the result will be a comparable higher chloride ingress, while a lower chloride ingress is achieved if the concrete is older at the first exposure to chlorides. The reason for this is probably that the pore-structure of the concrete is not fully densified, since the cement hydration has not reached its final level. The results indicate that a difference in age of one to two weeks at the first exposure to chlorides may give a significant different chloride ingress.Development in time for chloride ingress. The major part of the chloride ingress takes place during the first winter. After that only a slow increase in the chloride ingress has been observed. If an apparent diffusion coefficient, DF2, is determined special attention should be paid to the definition of the exposure time (total time or time of exposure to chlorides?).Effect of surface orientation on chloride ingress. The surface orientation (horizontal/vertical) does not seem to have any significance on the chloride ingress into concrete with low w/b (w/b=0.40). However, for concrete with high w/b (w/b=0.75) the chloride ingress and the penetration depths are higher for vertical surfaces.Effect of concrete composition. The concrete composition has a significant influence on the achieved chloride ingress, where, as expected, the w/b is the dominating factor. A low w/b gives a low chloride ingress and vice-versa. However, the effect on chloride ingress from use of silica-fume in the concrete is unclear sometimes silica-fume concrete has lower and sometimes higher chloride ingress compared to Portland cement concrete. Probable explanations could be the slower degree of reaction and lower chloride binding in silica-fume concrete compared to Portland cement concrete, which means that the age of the concrete at first exposure to chlorides is important. It is obvious that more research is needed to better explain the effect of silica-fume in concrete.
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| 9. |
- Lindvall, Anders, 1971
(författare)
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DURACRETE - Probabilistic preformance based durability design of concrete structures
- 1998
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Ingår i: Proceedings - 2nd International PhD Symposium in Civil Engineering. - 9634205607 ; , s. 93-99
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Konferensbidrag (refereegranskat)abstract
- The presented project is a first attempt to make probabilistic performance based durability designs of concrete structures. The performance based durability design is based upon realistic models that describes the future behaviour of the concrete and the environment. To make calculations it is necessary to quantify the parameters included in the chosen models. In this paper two models that describes the behaviour of concrete are presented and it is shown how the environmental parameters in the models are statistically quantified.
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| 10. |
- Lindvall, Anders, 1971
(författare)
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Environmental Actions and Response - Reinforced Concrete Structures exposed in Road and Marine Environments
- 2001
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The expenses for repair, maintenance and remediation of existing concrete structures have significantly increased. A large proportion of these expenses are due to problems related to a lacking durability of the structure. Thus, to reduce these expenses it is required to make a design of the service life of the structure in which the service life is explicitly specified.In this Licentiate thesis it is described how the service life of concrete structures can be determined. The factors that have an influence on the service life of a concrete structure are described. Furthermore it is described how the service life can be mathematically modelled and which techniques that can be used to determine the service life. Three principal factors that influence the service life of a concrete structure have been identified: (1) Material properties, (2) Execution during construction and (3) Environmental actions. Lots of efforts have been made to get a better understanding of how the material properties and to some extent the execution during construction influence the service life. However, very little has been made to clarify, which influence the environmental actions has on the service life.The deterioration of concrete can be predicted with two principal types of mathematical models namely physical models, which are based on theories of transport in porous materials, and empirical models, which are based on observations from structures. A few examples of different prediction models dealing with chloride penetration, carbonation and corrosion of the reinforcement are shown. It is also briefly described how a prediction of the service life can be made, with a performance based design methodology and probabilistic methods. To achieve reliable results with these prediction models it is required to have knowledge about boundary and initial conditions, e.g. how the environmental conditions vary inside and at the surface of the structure.Predictions of the service life can be made with two different methodologies: deem-to-satisfy rules, based on rules of thumb, and performance-based design. Usually probabilistic methods are used to predict the service life in a performance based design. However these kinds of predictions require extensive statistical quantifications of the parameters in the mathematical models. These statistical quantifications require good knowledge about which parameters that influence the deterioration of concrete, e.g. concrete composition, environmental actions at the surface of the structure and/or the response from the concrete.The environmental actions on a concrete structure have a decisive influence on the service life of the structure. The description of the environmental actions can be divided into four different levels depending on the dimensional scale. The objective is to determine the environmental actions at the surface of the concrete structure in terms of temperature, humidity and chloride conditions and the concentration of carbon dioxide. Furthermore the response from the material is of interest, e.g. how moisture and temperature distributions are distributed in a concrete structure. It is described how the environmental actions at the surface of concrete structure can be derived and what the response from the concrete is described.Finally a study of the response concrete structures exposed in road environments is presented. Seven bridges in and around Göteborg, around 30 years old, have been examined to determine the chloride penetration, moisture conditions and resistance against freeze/thaw actions. The analyses have been made on cores taken from selected positions on the bridges. The results from the study show large variations in chloride penetration between the examined bridges and even on a single part of a bridge, e.g. a column. A large part of these variations are assumed to arise due to variations in environmental actions at the surface of the bridges.
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