| 1. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Corrosion-induced cracking and bond behaviour of corroding reinforcement bars in SFRC
- 2017
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Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080569 ; , s. 123-126
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Konferensbidrag (refereegranskat)abstract
- In this study, an experimental programme has been carried out to investigate the influence of fibres on the onset of corrosion-induced splitting cracks. Cylindrical lollipop specimens with a centrally positioned Ø16 mm bar and varying cover depths from 40 to 64 mm were subjected to accelerated corrosion. A constant current of 100 μA/cm2 was impressed through the specimens and the electrical resistance between each rebar and an external copper mesh acting as cathode was monitored. The fibres, due to their confining effect, contributed to delay crack initiation, improve the post-peak bond behaviour and retain the initial splitting strength for corrosion levels of up to 8%.
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| 2. |
- Ghasemi, Yahya, 1982-, et al.
(författare)
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A method for obtaining optimum packing of aggregates for concrete at the onset of flow
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium. - Oslo, Norway : Nordic Concrete Federation. - 9788282080569 ; , s. 361-365
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Konferensbidrag (refereegranskat)abstract
- Particle packing models have been studied extensively during past decades and led to development of some complex and relatively accurate predictions of packing of granular materials. While the models are capable of calculating the packing density for different volumetric share of constitutes, the concept of optimum packing remains unclear. The study aims to define optimum packing based on particle packing theory and excess water layer theory .The approach makes it also possible to calculate amount of paste that is required to put a concrete mixture at the onset of flow. Some pilot tests conducted in the laboratory showed good agreement with calculated data.
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| 3. |
- Hösthagen, Anders, et al.
(författare)
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Thermal Crack Risk Estimations of Concrete Walls : Temperature and Strain Measurements Correlated to the Equivalent Restraint Method
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium. - Oslo, Norway : Nordic Concrete Federation. - 9788282080569
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Konferensbidrag (refereegranskat)abstract
- Self-induced non-elastic deformations in hardening concrete, caused by restrained volume changes due to thermal dilatation and moisture deformations, often leads to cracking. In crack risk analyses, determination of the degree of restraint is vital. One model to estimate the restraint and calculate the thermal crack risk is the Equivalent Restraint Method, ERM. The method has previously been analyzed but needs to be further examined and validated. Recordings of tunnel sections were performed and compared to calculated values by ERM. Satisfying correlation between theoretically estimated and observed temperatures, strains and time of through cracking was achieve which is promising for future implementation and testing of the method.
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| 4. |
- Jansson, Helen, 1964, et al.
(författare)
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Carbonation of concrete with mineral additions
- 2017
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Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080569 ; , s. 101-104
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Konferensbidrag (refereegranskat)abstract
- This study investigated how mineral addition, fly ash and slag (GGBS), influences carbonation, and how carbonation affects chloride migration and transport properties in mortar. Accelerated carbonation, Rapid Chloride Migration (RCM), capillary absorption tests (NT Build 368) and compressive strength tests (SS-EN 196-1) were conducted in a comparative study of mortar mixtures with different levels of mineral addition and w/b ratios. Carbonation rate increased and compressive strength was reduced with increased amount of mineral addition. The results also showed an interdependence between different deteriorating processes. Carbonation reduced the porosity, rate of reaching saturation and connectivity of the pore structure.
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| 5. |
- Lövgren, Ingemar, 1972
(författare)
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The influence of carbonation and age on salt frost scaling of concrete with mineral additions
- 2017
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Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080569 ; , s. 141-144
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Konferensbidrag (refereegranskat)abstract
- Resistance to salt frost scaling is tested by accelerated methods such as CEN/TS 12390-9. However, it has been shown that ageing and coupled deterioration mechanisms, like carbonation or leaching, can alter the frost resistance e.g. for concrete with high amount of slag (GGBS). This paper presents results from a laboratory study of concrete which have been exposed to accelerated carbonation at 1% CO2-concentration at different ages. The results show that exposing the specimens to accelerated carbonation at a young age result in an increased scaling and a carbonation depth corresponding to 10 year natural exposure. By increasing the age before the accelerated carbonation exposure the scaling is significantly reduced and the salt frost scaling resistance correlates better with field observations.
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| 6. |
- Nilforoush, Rasoul, et al.
(författare)
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Tensile breakout capacity of cast-in-place headed anchors in concrete
- 2017
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Ingår i: XXIIIth Symposium on Nordic Concrete Research & Developement. - Oslo, Norway. - 9788282080569 ; , s. 235-238
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Konferensbidrag (refereegranskat)abstract
- The influence of member thickness, size of anchor head, and orthogonal surface reinforcement on the tensile breakout capacity of cast-in-place headed anchors was studied both numerically and experimentally. The aim of this paper is to form a background for developing improved methods for the design of new fastening systems as well as the assessment of the current anchorage systems in practice. Numerical and experimental results showed that the tensile breakout capacity of anchor bolts increases by increasing the member thickness or if surface reinforcement is present. Furthermore, the anchorage capacity increases with increasing the anchor head size.
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| 7. |
- Nilimaa, Jonny, 1986-, et al.
(författare)
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Validation of the Swedish Crack Risk Estimation Models
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium. - Oslo : Nordic Concrete Federation. - 9788282080569 ; , s. 321-324
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Konferensbidrag (refereegranskat)abstract
- Thermal cracking may occur during the early hardening process of concrete as a result of the exothermic reactions between water and cement. An approach for thermal crack risk estimation and prevention was introduced in the Swedish design guidelines BRO 94. This paper studies and validates the current safety levels existing concrete structures. Three slab-frame structures were analysed and the preliminary crack risk estimations were compared to the actual cracking and post-estimations were carried out, using actual parameters. This paper shows that all the studied walls with a strain ratio over 70% were affected by thermal cracks.
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| 8. |
- Persson, Martin, et al.
(författare)
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Interface stresses in concrete bridge deck overlays subjected to differentialshrinkage
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium. - Oslo, Norway : Nordic Concrete Federation. - 9788282080569
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Konferensbidrag (refereegranskat)abstract
- Concrete overlays on bridge decks are expected to be more durable as compared with the more common asphalt solution. Besides stresses due to traffic load and temperature variations at service, the overlays are exposed to stresses due to long term shrinkage. Of interest is to evaluate the concrete overlay due to the shrinkage induced stresses at the composite interface. Three strategies have been employed to gain knowledge on the stresses; 1) use of non-destructive test systems via field observations, 2) a numerical study on a concrete composite slab tested in laboratory, 3) recordings of realistic shrinkage and climate data on a reference bridge using vibrating strain gauges and humidity probes in the newly cast concrete overlay. The data were used as input data for a linear elastic finite element model. This article demonstrates this last phase of the work.
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| 9. |
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| 10. |
- Sayahi, Faez, et al.
(författare)
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Effect of Water-Cement Ratio on Plastic Shrinkage Cracking in Self-Compacting Concrete
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium. - Oslo, Norway : Nordic Concrete Federation. - 9788282080569
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Konferensbidrag (refereegranskat)abstract
- Plastic shrinkage cracking is a mechanical phenomenon that occurs in the first few hours after casting the concrete in its mould. It is commonly believed that rapid and excessive moisture loss of the fresh concrete, mainly due to evaporation, plays a decisive role in the early age shrinkage. However, it is not always possible to justify all the plastic shrinkage incidents based on water evaporation solely. Instead, it seems that and interconnected correlation between evaporation, capillary pressure and hydration rate may offer better explanation. In this paper effect of water-cement (w/c) ratio on plastic shrinkage cracking of self-compacting concrete (SCC) is investigates. Four recipes with different w/c ratios (0.38, 0.45, 0.55 and 0.67) are tested by using Ring test method (NT BUILD 433). During the experiments evaporation, capillary pressure and internal temperature of the specimens were recorded from 60 minutes after casting up to 18 hours, at which the length and width of the cracks were measured. The results show lower risk of cracking when w/c ratio is between 0.45 to 0.55. However, the specimens with 0.38 and 0.67 w/c ratio experienced higher cracking tendency, especially the latter, in which severe cracking was observed.
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