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- Andersson, Louise
(författare)
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Continuous Preventive Bridge Maintenance : Effect of High Pressure Washing on Concrete Bridges
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Sweden, as in many other countries, preventive maintenance of structures andbridges is considered important. It provides several benefits such as prolonged lifespan or service life, less need for repair, and hopefully reduced costs and lowerenvironmental impact.A large part of Sweden’s bridge stock is getting quite old. The idea that small actionscan improve and/or prolong the status of the bridge and postpone needs for repairor prevent damage with a reduction in life cycle cost is generally in the owner’sinterest. One such preventive maintenance measure is the annual washing ofbridges. While clear positive effects have been observed on the expansion joints,drainage system, and the bridge’s visual appearance, an important question is howthe washing affects chloride ingress, mainly from de-icing salts, in reinforcedconcrete bridge members. The hypothesis is that the high-pressure washing cleansaway the contaminants on the surface and in the long run reduces the chloridecontent. While the practical experience has been positive in Sweden, no research hasyet been done concerning the effect of high-pressure washing on chloride ingress inconcrete bridges.A study has been conducted on the preventive bridge maintenance practice of theSwedish Transport Administration (STA) and Swedish municipalities. This work hasbeen based on a literature review, a survey of municipalities’ bridge maintenance,and practical participation with contractors during annual maintenance. Field andlaboratory tests were carried out on the effect of washing on chloride ingress in twotypes of concrete. A field station was installed on an edge beam of a bridge and wasfollowed over three years’ exposure including winter seasons, winter maintenance,and annual washing in June. Also, an accelerated test method was developed in thelaboratory to simulate the yearly exposure and test the effect of high- pressurewashing in a long-term simulation over just a few weeks.The practical aspects of bridge maintenance seem to be quite similar betweenSweden and in other countries. However, in terms of descriptions of and availablemeans for maintenance and repairs, there seem to be larger differences. For the fieldstation, the results after one year’s exposure do not show anything more than theanticipated difference in chloride ingress between the two concrete types understudy. For year two, a slight difference indicated that washed samples had a reducedchloride content. For year three, however, there was no distinct difference betweenivwashed and unwashed samples. The reasons for this need to be further investigatedand examined. This will be done in the continuous tests of field exposure.The laboratory test method has been developed and successively improved. The shape and levels of chloride ingress are reasonable and comparable with fieldsamples. However, there is a need to examine the effect of natural rain exposurewhich might have the same or greater effect of diluting the chloride content aswashing the surface once a year. Other factors also need to be considered, such aswhen and how often the maintenance is performed. A first step to be able to examinethis has been completed through the development of the accelerated test method.
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- Butt, Ali Azhar, et al.
(författare)
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Environmental friendly wax modified mastic asphalt
- 2009
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Konferensbidrag (refereegranskat)abstract
- Mastic asphalt products (Gussasphalt) require high working temperatures, and harder requirements concerning bitumen fumes and carbon dioxide emissions. Consequently, the need of a new means of producing and placing mastic asphalt at lower temperatures is particularly large. One way of reducing asphalt mixture temperature is by using special flow improving additives like wax. This technique has successively been tried for polymer modified mastic asphalt used for bridge decks and parking areas in Sweden. However, there still are uncertainties about possible negative impact on crack susceptibility at lower temperatures due to wax additives.In this study, 4% montan wax (Asphaltan A) was used for one particular polymer modified mastic asphalt product. Type and amount of wax additive was selected based on results from earlier studies. The impact on binder, binder/filler mixtures and mastic asphalt from production was tested in the laboratory, focusing on low temperature performance. The bending beam rheometer (BBR) was used for determining low temperature creep compliance and the tensile stress restrained specimen test (TSRST) for determining fracture temperatures. Binder properties were determined using dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy and conventional tests (softening point, penetration, elastic recovery, breaking point, viscosity and storage stability). Aging was performed using the rolling thin film oven test (RTFOT) at 200°C.As expected, the addition of wax to the polymer modified binder showed a viscosity reduction at higher temperatures, corresponding to a similar positive effect of more than 10°C on production and laying temperature for the mastic asphalt. DMA and BBR results showed some increase in stiffness and a more elastic response of the wax modified binder at medium and low temperatures. The TSRST fracture temperature was 5 °C higher for the mastic asphalt containing wax, indicating however no dramatic negative impact on crack susceptibility.
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- Dar, Pe'er, et al.
(författare)
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Cell-free DNA screening for prenatal detection of 22q11.2 deletion syndrome.
- 2022
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Ingår i: American journal of obstetrics and gynecology. - : Elsevier BV. - 1097-6868 .- 0002-9378. ; 227:1
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Tidskriftsartikel (refereegranskat)abstract
- Prenatal screening has historically focused primarily on detection of fetal aneuploidies. Cell-free DNA (cfDNA) now enables noninvasive screening for subchromosomal copy number variants, including 22q11.2 deletion syndrome (22q11.2DS or DiGeorge syndrome), which is the most common microdeletion and a leading cause of congenital heart defects and neurodevelopmental delay. Although smaller studies have demonstrated the feasibility of screening for 22q11.2DS, large cohort studies with postnatal confirmatory testing to assess test performance have not been reported.To assess the performance of SNP-based cfDNA prenatal screening for detection of 22q11.2DS.Patients who had SNP-based cfDNA prenatal screening for 22q11.2DS were prospectively enrolled at 21 centers in 6 countries. Prenatal or newborn DNA samples were requested in all cases for genetic confirmation with chromosomal microarray. The primary outcome was sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of cfDNA for detection of all deletions, including the classical deletion and nested deletions that are ≥500kb, in the 22q11.2 low copy repeat A-D region. Secondary outcomes included the prevalence of 22q11.2DS and performance of an updated cfDNA algorithm that was evaluated blinded to pregnancy outcome.Of 20,887 women enrolled, genetic outcome was available in 18,289 (87.6%). Twelve 22q11.2DS cases were confirmed in the cohort, including five (41.7%) nested deletions, yielding a prevalence of 1:1524. In the total cohort, cfDNA reported 17,976 (98.3%) as low risk for 22q11.2DS and 38 (0.2%) as high-risk; 275 (1.5%) were non-reportable. Overall, 9 of 12 cases of 22q11.2 were detected, yielding a sensitivity of 75.0% (95% CI: 42.8, 94.5); specificity of 99.84% (95% CI: 99.77, 99.89); PPV of 23.7% (95% CI: 11.44, 40.24) and NPV of 99.98% (95% CI: 99.95, 100). None of the cases with a non-reportable result was diagnosed with 22q11.2DS. The updated algorithm detected 10/12 cases (83.3%; 95% CI: 51.6-97.9) with a lower false positive rate (0.05% vs. 0.16%, p<0.001) and a PPV of 52.6% (10/19; 95% CI 28.9-75.6).Noninvasive cfDNA prenatal screening for 22q11.2DS can detect most affected cases, including smaller nested deletions, with a low false positive rate.
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- Dar, Pe'er, et al.
(författare)
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Cell-free DNA screening for trisomies 21, 18 and 13 in pregnancies at low and high risk for aneuploidy with genetic confirmation
- 2022
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Ingår i: American journal of obstetrics and gynecology. - : Elsevier BV. - 1097-6868 .- 0002-9378. ; 227:2
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Tidskriftsartikel (refereegranskat)abstract
- Cell-free DNA (cfDNA) non-invasive prenatal screening for trisomy (T) 21, 18, and 13 has been rapidly adopted into clinical practice. However, prior studies are limited by lack of follow up genetic testing to confirm outcomes and accurately assess test performance, particularly in women at low-risk for aneuploidy.To compare the performance of cfDNA screening for T21, T18 and T13 between women at low and high-risk for aneuploidy in a large, prospective cohort with genetic confirmation of results.A multicenter prospective observational study at 21 centers in 6 countries. Women who had SNP-based cfDNA screening for T21, T18 and T13 were enrolled. Genetic confirmation was obtained from prenatal or newborn DNA samples. Test performance and test failure (no-call) rates were assessed for the cohort and women with low and high prior risk for aneuploidy were compared. An updated cfDNA algorithm, blinded to pregnancy outcome, was also assessed.20,194 were enrolled at median gestational age of 12.6 weeks (IQR:11.6, 13.9). Genetic outcomes were confirmed in 17,851 (88.4%): 13,043 (73.1%) low-risk and 4,808 (26.9%) high-risk for aneuploidy. Overall, 133 trisomies were diagnosed (100 T21; 18 T18; 15 T13). cfDNA screen positive rate was lower in low- vs. high-risk (0.27% vs. 2.2%, p<0.0001). Sensitivity and specificity were similar between groups. The positive predictive value (PPV) for the low and high-risk groups was 85.7% vs. 97.5%, p=0.058 for T21; 50.0% vs. 81.3%, p=0.283 for T18; and 62.5% vs. 83.3, p=0.58 for T13, respectively. Overall, 602 (3.4%) patients had no-call result after the first draw and 287 (1.61%) after including cases with a second draw. Trisomy rate was higher in the 287 with no-call results than patients with a result on a first draw (2.8% vs. 0.7%, p=0.001). The updated algorithm showed similar sensitivity and specificity to the study algorhitm with a lower no-call rate.In women at low-risk for aneuploidy, SNP-based cfDNA has high sensitivity and specificity, PPV of 85.7% for T21 and 74.3% for the three common trisomies. Patients who receive a no-call result are at increased risk of aneuploidy and require additional investigation.
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| 7. |
- Edwards, Ylva, et al.
(författare)
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Beläggningssystem på betong i parkeringshus och garage : en översikt
- 2012
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Rapport (refereegranskat)abstract
- Skador i form av rostande armering i olika typer av parkeringshus och garage uppstår enligt CBIs erfarenheter huvudsakligen i bjälklag, ramper och i de nedre delarna av väggar och pe-lare. Men denna typ av skador kan undvikas med rätt betongkvalitet, tillräckligt tjocka täck-skikt över armeringen och väl fungerande tätskiktsbeläggning. _x000D_ _x000D_ Det finns olika typer av beläggningar för parkeringshus. Mest vanligt är polymermodifierad gjutasfalt (PGJA) på tätskiktsmatta, men även betongpågjutningar förekommer. Sedan 2000-talets början har det blivit allt vanligare med olika typer av härdplastbaserade beläggningar. En anledning till detta är att beläggningen kan utformas i valfri färgsättning vilket ger stora estetiska möjligheter. Det är emellertid viktigt att valet av en sådan förhållandevis tunn be-läggning inte görs utan att krav samtidigt ställs på beläggningens egenskaper. Slitage, sprick-bildning och vidhäftningsförluster utgör de största problemen och utmaningarna för parker-ingsdäck. Beträffande beläggningens slitstyrka utsätts denna för dubbdäcksslitage i svenska parkeringshus, vilket inte är fallet i de flesta andra länder. Detta måste beaktas vid val av be-läggning och inte minst provningsmetod för bestämning av nötningsresistens hos belägg¬ningen i fråga. Beständighet mot klorider och andra på ett parkeringsdäck förekommande kemikalier är en annan viktig egenskap som måste redovisas._x000D_ _x000D_ I denna rapport beskrivs bland annat några av de olika typer av härdplastbaserade belägg-ningssystem som marknadsförs till parkeringshus och garage i Sverige, samt ges viss grund-läggande information om uppbyggnad, egenskaper och krav som kan ställas på systemen. Bitumenbaserade system, i huvudsak med tätskiktsmatta och gjutasfalt, behandlas också, lik-som specifikationer. Exempel på beläggningar på marknaden listas och en bilaga med refe-rensobjekt och exempel på förekommande skador avslutar rapporten._x000D_ _x000D_ I slutsatserna konstateras bland annat att:_x000D_ • En relevant och för parkeringsdäck anpassad kravspecifikation bör tas fram för att under-lätta för såväl beställare som tillverkare och entreprenörer. Bestämning av slitstyrka är centralt._x000D_ • Det finns behov av ytterligare forskningsinsatser inom området beläggningssystem på betong i parkeringshus och garage. Val av system, inverkan av betongkvalitet, underhålls- och reparationsåtgärder samt uppföljningar av befintliga system bör tas upp. En annan åt-gärd kan vara att även använda katodiskt skydd.
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