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Silfwerbrand J.L.,Swedish Cement and Concrete Research Institute CBI | Silfwerbrand J.L.,KTH Royal Institute of Technology
American Concrete Institute, ACI Special Publication | Year: 2010

During the last decade, the Swedish Road Administration (SRA) has transferred resources from corrective to preventive bridge maintenance. Presently, 10 to 15 percent of the budget is devoted to preventive maintenance whereas corrective maintenance, repair, and reconstruction comprise the remaining 85 to 90 percent. This reallocation has resulted in considerable efficiency gains but further savings are likely to be large. Preventive maintenance aims at measures to maintain the function of the bridge structure. Frequent measures include water washing, cleaning, vegetation removal, crack repair, material refill, and stretching of bridge railings. SRA has defined a series of technical requirements to harmonize the preventive bridge maintenance. Several technical requirements state that a structural element or element part "should be 95 percent clean". SRA has also developed methods to verify that the technical requirements are fulfilled. However, the scientific basis for the relationship between the technical requirements and the function of the bridge structure is unknown or weak. The verification methods are not always unquestionable. The paper contains a critical review of the technical demands for preventive bridge maintenance in Sweden. Do they adequately promote durability and long-lasting service life? Are the prescribed requirement levels appropriate? Could the technical requirements be replaced by other and better requirements? How do they look like in an international comparison? There is a general belief that performance-specified contracts would be more cost-effective than other contract types. Do the Swedish demands facilitate or obstruct performance-specified contracts for bridge maintenance? The questions are discussed in the paper that also contains a summary of a Swedish pilot study conducted at the Swedish Cement and Concrete Research Institute.


PubMed | Swedish Cement and Concrete Research Institute CBI, Geological Survey of Sweden, Sahlgrenska University Hospital and KTH Royal Institute of Technology
Type: | Journal: Journal of environmental radioactivity | Year: 2016

The reference level for effective dose due to gamma radiation from building materials and construction products used for dwellings is set to 1mSv per year (EC, 1996, 1999), (CE, 2014). Given the specific conditions presented by the EC in report 112 (1999) considering building and construction materials, an I-index of 1 may generate an effective dose of 1mSv per year. This paper presents a comparison of the activity concentrations of (4)(0)K, (226)Ra and (232)Th of aggregates and when these aggregates constitute a part of concrete. The activity concentration assessment tool for building and construction materials, the I-index, introduced by the EC in 1996, is used in the comparison. A comparison of the I-indices values are also made with a recently presented dose model by Hoffman (2014), where density variations of the construction material and thickness of the construction walls within the building are considered. There was a 16-19% lower activity index in concretes than in the corresponding aggregates. The model by Hoffman further implies that the differences between the I-indices of aggregates and the concretes final effective doses are even larger. The difference is due, mainly to a dilution effect of the added cement with low levels of natural radioisotopes, but also to a different and slightly higher subtracted background value (terrestrial value) used in the modeled calculation of the revised I-index by Hoffman (2014). Only very minimal contributions to the annual dose could be related to the water and additives used, due to their very low content of radionuclides reported.


Dose M.,Swedish Cement and Concrete Research Institute CBI | Silfwerbrand J.,KTH Royal Institute of Technology | Jelinek C.,Geological Survey of Sweden | Tragardh J.,Swedish Cement and Concrete Research Institute CBI | Isaksson M.,Gothenburg University
Journal of Environmental Radioactivity | Year: 2016

The reference level for effective dose due to gamma radiation from building materials and construction products used for dwellings is set to 1 mSv per year (EC, 1996, 1999), (CE, 2014). Given the specific conditions presented by the EC in report 112 (1999) considering building and construction materials, an I-index of 1 may generate an effective dose of 1 mSv per year. This paper presents a comparison of the activity concentrations of 4 0K, 226Ra and 232Th of aggregates and when these aggregates constitute a part of concrete. The activity concentration assessment tool for building and construction materials, the I-index, introduced by the EC in 1996, is used in the comparison. A comparison of the I-indices values are also made with a recently presented dose model by Hoffman (2014), where density variations of the construction material and thickness of the construction walls within the building are considered. There was a ~16-19% lower activity index in concretes than in the corresponding aggregates. The model by Hoffman further implies that the differences between the I-indices of aggregates and the concretes' final effective doses are even larger. The difference is due, mainly to a dilution effect of the added cement with low levels of natural radioisotopes, but also to a different and slightly higher subtracted background value (terrestrial value) used in the modeled calculation of the revised I-index by Hoffman (2014). Only very minimal contributions to the annual dose could be related to the water and additives used, due to their very low content of radionuclides reported. © 2016 Elsevier Ltd.


Bellopede R.,Polytechnic University of Turin | Castelletto E.,Polytechnic University of Turin | Schouenborg B.,Swedish Cement and Concrete Research Institute CBI | Marini P.,Polytechnic University of Turin
Environmental Earth Sciences | Year: 2016

The bowing phenomenon is so relevant that two projects, EU funded, from 1999 studied it and a European Standard to assess the resistance to thermal and moisture cycles (influencing bowing) has been recently adopted. In particular, according EN 16306: 2013, measurements of bowing and flexural strength should be performed before and at the end of the ageing cycles. Additional non-destructive tests are recommended, but are not compulsory for the standard. Moreover, Annex A of EN 16306 contains guidance on the limit values for the selection of marble types suitable for outdoor uses, especially façade applications. Eleven varieties of marble have been tested by means of this laboratory ageing test. Non-destructive tests such as the measurements of ultrasonic pulse velocity (UPV), adjacent grains analysis, open porosity, and water absorption have been executed together with the conventional flexural strength test. The results obtained from image analysis on thin sections indicate that the AGA index may not always be correlated with the other tests: amount of bowing, loss of flexural strength, or loss of UPV. Some consideration of the decrease in mechanical resistance and the bowing in relation to the variety of marble tested and the limit values indicated in Annex A of EN 16306 can be noted. It is known that bowing and rapid strength loss occur in some varieties of marble when used as exterior cladding and other exterior applications. Additional conclusions have been drawn: bowing and flexural strength correlate well and can be used to assess the suitability of the marble to be employed in outdoors. © 2016, Springer-Verlag Berlin Heidelberg.


Berg F.,Chalmers University of Technology | Johansson D.,Chalmers University of Technology | Lundgren K.,Chalmers University of Technology | Plos M.,Chalmers University of Technology | Zandi Hanjari K.,Swedish Cement and Concrete Research Institute CBI
Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management | Year: 2012

Corrosion of reinforcement is one of the most common causes of deterioration in reinforced concrete bridges. Anchorage, prior to shear and bending moment resistance, is the main uncertainties in the evaluation of the structural behavior of corroded reinforced concrete bridges. Thus, to assess the remaining load-bearing capacity of deteriorated existing bridges, models to estimate the remaining bond and anchorage capacity are needed. Most of our knowledge on the structural behavior of corroded reinforced concrete structures is based on experimental investigations of artificially corroded concrete specimens. In this study, the anchorage capacity of naturally corroded steel reinforcement was investigated experimentally. The test specimens were taken from edge beams of a bridge, Stallbackabron, in Sweden. Since the dimensions and the amount of reinforcement were given on beforehand, it was only the test set-up which could be chosen freely. A test set-up consisting of a four point bending test indirectly supported with suspension hanger was considered to be the best alternative with the least disturbance and influence of the natural damages. Detailed design was done by using a non-linear finite element method. It was seen that the edge beams needed to be strengthened with transverse reiforcement, else they would have failed in a local failure at the suspension hole or in shear. The technique adopted for the strengthening was an internal mounting of steel reinforcement using epoxy as adhesive. The bond and anchorage behavior was examined in tests through measurements of applied load, free-end slip and mid-span deflection. A first test showed that additional measures were needed to ensure anchorage of the strengthening bars. In subsequent tests, they were therefore anchored at the top of the beam with hexagonal nuts and flat steel plates. In two following tests, the beams failed in a splitting induced pull-out failure, i.e. anchorage failure was achieved as wanted. © 2012 Taylor & Francis Group.


Gram A.,Swedish Cement and Concrete Research Institute CBI | Silfwerbrand J.,Swedish Cement and Concrete Research Institute CBI | Lagerblad B.,Swedish Cement and Concrete Research Institute CBI
Cement and Concrete Research | Year: 2014

In the mix design process of cementitious suspensions, an adequate rheology of the cement paste is crucial. A novel rheological field test device for cementitious fluids is presented here and investigated theoretically, by computer simulation and by lab tests. A simple flow stoppage test with a timed spread passage point provides accurate rheological parameters according to the Bingham material model. Values for yield stress and plastic viscosity are obtained for a test specimen of no more than 19.75 · 10- 6 m3 of fluid. This volume is equivalent to 19.75 g of water at room temperature. Such a small volume allows reliable tests even for small amounts of fillers. Promising results show that both yield stress and plastic viscosity can be determined by this simple test. This novel rheological test method also enables the correlation of different rheological equipment used by different laboratories. © 2014 Elsevier Ltd.

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