Bridges are an important part of the infrastructure. For the bridges to have the longest possible service life with minimum repairs, the maintenance is of great importance. One type of bridge maintenance that is rarely researched is the continuous preventive maintenance. The continuous preventive maintenance consists of removal of vegetation, cleaning of bridge joints and drainage systems as well as high-pressure washing of the structure. The effects of washing is heavily discussed but not properly researched. A study on the effectiveness of washing concrete is therefore being conducted. A field experiment has been initiated where concrete specimens are installed on an edge beam of a road bridge. The specimens are of two recipes where one represents an old bridge with rather high water-cement ratio and the other one represents a new bridge with a low water-cement ratio. 50% of the specimens are washed annually, while the others are not. Each year samples are collected and tested for a chloride profile. The results for the first year of exposure have been determined. They are promising but are still only very preliminary. The effect of washing, if any, will be visible after a longer exposure.

Electroosmosis is an electrokinetic phenomena which is applied in some technical fields. It is also applied large scale for transport of moisture out of basements. We see the method of electroosmosis as an opportunity for solving moisture problems in basements. However, there is a need to develop both the technology for the method and the understanding about what to expect out of it. Better methods are needed to predict whether the method will work in a particular case. © The Authors.

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.

This report is a summary of the present level of knowledge with regard to aggregates in concrete. It focuses on the composition of aggregates and the mineral and petrographical variations which affect the quality and properties of the aggregates. _x000D_ _x000D_ The report starts with a brief description of how aggregates reacts in fresh, new and hardened concrete. This information provides the basis for understanding why it is important to require a certain quality from aggregates in concrete. After that there is a chapter about the different types of rocks and their composition. The description is a brief summary of the geological know-how required to understand the variations of aggregates and the underlying reasons for many of the positive and negative properties of concrete. _x000D_ _x000D_ The second half of the report, from chapter 5 onwards, mainly deals with how to examine and describe aggregates. The description is based on the standards which are being drawn up in Europe, the so-called CEN-standards. As soon as they are ready, they will be used as Swedish standards. The regulations covering aggregates in concrete, which are based on international experience, are more comprehensive and slightly more detailed than those we have been used to in Sweden. _x000D_ _x000D_ Finally, the report contains a list of all the test methods which can be used to identify components in aggregates which can be deleterious to concrete.

Cement-based materials are fundamentally unstable in a long time perspective. With time the concrete will change properties both as a consequence of recrystallisation and chemical interaction with the environment.The hydration products are stabilized by the high pH within the concrete. Thus, when the cement paste has equilibrated with the environment new phases will form. Not only reactions inside the cement paste are of interest in this context. It is also important to consider reactions with the aggregate phase and in particular reactions with the silica component in the aggregate phase due to the high pH from alkali hydroxides and subsequent reactions of the alkali silica hydrate phases. This has been a special subject of research at CBI. The rate of the chemical reactions in concrete in general is governed by a combination of dissolution mechanisms, diffusion and permeability/porosity. The main controlling factor is the dissolution of calcium hydroxide (portlandite) which buffers and controls the pH in the cement paste. Another important factor is the permeability of the concrete. During the first period the permeability will decrease as a consequence of continued hydration and recrystallization of the cement paste. _x000D_ _x000D_ One of the main difficulties with a conceptual model for concrete degradation is the change in the geochemical environment with time.The degradation process must be treated as a sequence of different degradation mechanisms. During the first period the concrete will alter as a result of contact with atmospheric gases especially carbon dioxide which will carbonate the surface. Later the degradation will mainly be governed by the composition of the groundwater with which it will try to equilibrate. Thus the composition of both the groundwater and the concrete will change. Considering the groundwater chemical conditions at repository depths (500 m), it is possible that with time the groundwater will change composition from normal to saline. This may in fact be an advantage because the solubility of the cement paste components decreases. However, the concrete itself will influence the groundwater composition and create an aureole with increased pH around it. Most of the components in both the fresh and saline water will not be harmful to concrete. One of the problems may be the chlorine anions, as this anion may substitute for sulphate in some of the cement phases. This will not degrade the concrete but the sulphates in the cement may be released to the groundwater. The end product of the concrete, after leaching and after the pH buffer capacity has been lost, will be a mix of metastable calcium silicate hydrates, zeolite and clay minerals. _x000D_

Denna rapport omfattar slutrapporteringen av forskningsprojektet - Ny provningsmetodik för bedömning av bindemedlets korrosionsskyddande förmåga i betong – Underlag till LCA och livslängdsbedömning. I rapporten redovisas resultat från elektrokemiska undersökningar utförda på laboratorium och korrosionsprovningar i fält. Undersökningarna har genomförts av Swerea KIMAB, RISE CBI Betonginstitutet (väst och öst) samt Chalmers. Projektets mål har varit att genom en nationell samling av expertis ta fram en ny provningsmetodik som på ett enkelt och tillämpbart sätt ska utvärdera olika bindemedels korrosionsskyddande förmåga i betong. I denna undersökning har framför allt tiden till initiering av korrosion (gropfrätning) från det att kloriderna har nått stålytan och tills gropfrätning har initieras på stålytan undersökts. Tre olika accelererade elektrokemiska mätmetoder har använts och jämförts:

 Potentiostatisk mätmetod

 Potentiodynamisk mätmetod

 Galvanostatisk mätmetod

Den framtagna provningsmetodiken med framställning av provkroppar har visat sig fungera väl. För att minska spridningen är det emellertid viktigt att använda en homogen och rengjord stålyta utan glödskal. Glödskalet avlägsnas lämpligast genom slipning eftersom betning kan bygga upp ett passivskikt på stålytan. För att undvika att betongrester fastnar på stålytan ska släta provstänger användas.

Sammanfattningsvis kan sägas att resultaten från laboratorie- och fältmätningarna samt analyser av bindemedlens korrosionskänslighet genom TG- och XRD-analyser visade att denna kombination av mätningar ger ett bra verktyg att bedöma den korrosionsskyddande förmågan hos olika bindemedel. En sammanställning av rangordningen för bindemedlens korrosionsskyddande förmåga redovisas i tabellen nedan.

Den korrosionsskyddande förmågan hos de undersökta bindemedlen rangordnas från en sammanvägning av de olika provningsmetoderna:

 bra < 1,5 och

 1,5 ≥mindre bra ≤2,5 och

 dåligt > 2,5.

Som rangordningen visar i tabellen så har bindemedel med slagg och portlandcement med hög C 3A en bra korrosionsskyddande förmåga. Detta beror till största delen på kapaciteten att bilda Friedels salt från monosulfat under härdningsprocessen. Bindemedel som har en låg korrosionsskyddande förmåga har ett lågt C3A-innehåll och en inblandning av flygaska och/eller silika. Det medför dessutom en utspädningseffekt på förmågan att bilda Friedels salt.

In order to investigate if alkali-silica reaction (ASR) have an influence on the frost resistance of concrete both field and laboratory concretes were examined under the microscope and tested. Water absorption/desorption tests and freeze-thaw tests were carried out on laboratory concretes and water absorption tests on field concrete. _x000D_ _x000D_ The laboratory concrete samples were prepared with a deleterious amount of a reactive natural aggregate. At the same time reference samples with unreactive material were prepared. The concretes were prepared with an air-entrainment agent and contained two different air void contents, 4.6 % and 7.5 %, and W/C ratios of 0.40 and 0.55 respectively. Prior to the testing the concretes which contained reactive material had developed ASR expansion and cracking. For the concretes which developed cracks due to ASR expansion, it is shown that the frost resistance is significantly decreased. This is more pronounced for the concrete with the lower W/C ratio and air-void content. This concrete also had a lower level of critical water saturation when affected by ASR. It was found that the expansion during freeze-thaw testing is directly proportional to the initial crack widths caused by ASR. _x000D_ _x000D_ A petrographic examination of core samples from field structures which showed cracking due to both ASR and frost attack was carried out. In the microscope it was observed that the already existing ASR cracks had induced frost attack. The cement paste along vertical ASR- cracks contained portlandite filled air-voids with radiating micro cracks typical for frost attack. This indicates that open cracks provide new surfaces from which frost attack can progress. In the microscope it is possible to distinguish between cracking caused by ASR and frost attack. The geometry and spacing of the cracks as well as the alteration products are different. _x000D_ _x000D_ The microscope examination also showed that frost action induces cement deterioration. This is brought by micro cracking followed by leaching of calcium hydroxide and sulphates from cement components. Dissolution and leaching is caused by water movements during recurrent cycles of freezing and thawing which eventually leads to the breakdown of cement gel components. The dissolved constituents precipitates in cracks and air voids as secondary products such as portlandite and ettringite. Observations were made of micro cracks radiating out from air voids which has been filled with portlandite. This can be taken as evidence for expansion of water in air voids during freezing. Massive deposits of portlandite and ettringite in cracks and air-voids seem to be significant for frost attack. The solubility of calcium hydroxide is higher at lower temperatures and temperature gradients control whether calcium hydroxide is dissolved or precipitated. Portlandite mobilisation is marginal in concretes only affected by ASR but significant in concretes affected by frost attack. In concretes only affected by ASR ettringite crystallisation in open spaces is commonly observed but is far from the amounts observed in concretes affected by frost attack.