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Corrosion processes of steel in concrete contaminated with chlorides take place as macrocell corrosion as well as self‐corrosion (i.e., microcell corrosion). While macrocell corrosion can be detected by element current measurement, self‐corrosion cannot be precisely determined electrochemically. This results in deviations in corrosion investigations between the mass losses calculated coulometrically from macrocell current measurements and the actual, corrosion‐related gravimetric mass losses. This is relevant in practice as part of corrosion monitoring. In the following, a simple approach is presented by considering this self‐corrosion current mathematically in the macrocell current measurement. The empirical regression functions determined for this purpose can be applied to a large number of different influencing parameters and allow the determination of the cumulative steel degradation at time‐varying macrocell current densities under consideration of different safety levels. This allows a much more accurate estimation of the actual corrosion‐induced mass losses during corrosion monitoring than previously possible. [ABSTRACT FROM AUTHOR]

Corrosion Monitoring in Reinforced Concrete Structures – New Research Results Corrosion of reinforcing steel caused by de‐icing salt and carbonation leads to considerable repair costs in middle Europe every year. The use of corrosion monitoring on reinforced concrete structures opens up new possibilities for interpreting whether damage has already occurred and how quickly it is progressing. Thus, the penetration of the depassivation front into a chloride‐loaded structure can be determined, or, if corrosion is already taking place, the magnitude of the damage progress can be estimated. By installing appropriate sensors in existing structures, the repair success can be verified after completion of repair work in accordance with procedure 8.3 of TR IH. To date, however, there is no code of practice for corrosion monitoring. In 2018, a leaflet B12 of the DGZfP was published for the first time, which can serve as a guideline. In addition, a broad WIPANO research project called "KoMICS" on open questions on corrosion monitoring has been carried out in Germany over the past three years. The findings of this project will be incorporated into a DAfStb Guidline, which is currently being edited. Relevant findings of the investigated task part of the research project at the Munich University of Applied Sciences HM are presented below. [ABSTRACT FROM AUTHOR]

LIBS and electrolyte resistance investigations – Components of an in‐depth structural diagnosis of chloride‐contaminated reinforced concrete Chlorides can lead to damaging pitting corrosion at the reinforcement in reinforced concrete components, which is not necessarily visible from the outside. In order to select an appropriate repair method as specifically as possible the degree of damage and the damage potential of the components have to be identified. Besides conventional methods of building diagnostics two additional investigation methods are also being applied more often. For example, valuable additional information on the chloride distribution within the structure can be generated through targeted investigations with LIBS (Laser induced Breakdown Spectroscopy) analysis. By determining the electrolyte resistance, components can also be assessed with regard to the water content and tightness and thus with regard to the damage potential. The application of both methods in structural diagnostics are presented below. Finally, it is shown how, depending on the repair method carried out according to the Technical Rule "Maintenance of Concrete Structures (TR‐IH)" of the DIBt, different NDT methods have different importances and values. In practice, this should enable a more tailor‐made structural diagnosis. [ABSTRACT FROM AUTHOR]

Translation abstract Leaching‐induced corrosion of the reinforcing steel in water‐bearing separating cracksWhen water flows through separating cracks or construction joints, the cement paste leaches out, and alkalinity is reduced. As with carbonation, this decrease in pH leads to the loss of the passive layer, which is limited to the directly adjacent area. The progress of corrosion may depend on the water exchange rate. This presented study investigates the influence of the water pressure level on test specimens with crack widths between 0.20 and 0.25 mm (mean values) on the onset of depassivation and the corrosion rate. The test specimens were exposed to demineralised water at a hydrostatic pressure of 0.04 bar, 0.20 bar or 1.00 bar and monitored for corrosion. A few days after the start of exposure, high macroelement currents flow in all test specimens. Later, due to self‐healing, the flow stops at 0.04 bar, and the macroelement currents decrease significantly. In contrast, the reduced but steady flow at 0.20 and 1.00 bar leads to a continuous corrosion progression. While a (planned) longer interruption of the water supply results in repassivation of the steel, renewed pressurisation significantly increases both the flow and corrosion rates. The leaching manifests in an increase in the pH of the effluent water and a reduced calcium concentration in the crack area. [ABSTRACT FROM AUTHOR]

Repair of chloride‐contaminated RC‐components by application of a coating – Investigations on the application limits of methods 7.7 and 8.3 The technical rule of the German Institute for Building Technology (Deutsches Institut für Bautechnik – DIBt) "Maintenance of concrete structures" (TR‐IH) introduced in January 2021 enables two methods for the repair of chloride‐contaminated structures by applying a surface protection system with chlorides remaining in the concrete (to a large extend). The repair method 7.7 "Coating of chloride‐containing concrete" may be applied if the reinforced steel is still passive and the chloride load in the concrete cover ensures a distance of the critical chloride content from the reinforced steel of 10 mm. By developing a closed solution of the diffusion‐controlled chloride redistribution after applying the coating even with partially water‐saturated concretes and a parameter study, it could be shown that the maximum remaining chloride content in the concrete cover may be 2.0 wt.‐%/cem. The repair method 8.3 "Increase of electrical resistance by coating", on the other hand, may also be applied with active reinforcement corrosion. Extensive investigations have widely confirmed the application limits mentioned in the TR‐IH and further sharpened them with regard to concrete quality and the type of surface protection system. Finally, the method is only applicable to chloride levels below 1.0 wt.‐%/cem (considering a chloride redistribution) with a low risk. [ABSTRACT FROM AUTHOR]

With the implementation of the repair method "increasing the electrical resistivity by coating" (MR 8.3), no direct repassivation of the reinforcing steel is initially intended. The success of the repair is rather linked to the change of the corrosion‐relevant parameters over time. These include an increase in the concrete resistivity due to dehydration and gradual decrease in corrosion currents and driving voltages on the reinforcing steel. Within the scope of a research project funded by the German Research Foundation (DFG), application limits for the repair principle W‐Cl could be defined. The chloride content present in the concrete at the rebar is the significant limiting factor for the application. While the corrosion activity even with moderately dehydrated specimens under diffusion‐retarding coatings at chloride contents of 1 wt% Cl−/c is in the range of the passive current density, this cannot be generally determined for chloride contents of 2 wt% Cl−/c. The type of coating has a decisive influence on the dehydration of the concrete. For example, less dense concretes under a permeable coating (acrylic dispersion/OS 4) can dry out to such an extent that the passive current density is reached. With semipermeable coatings and the presence of high chloride contents of 2 wt% Cl−/c, the repair principle W‐Cl does not lead to success according to the available test results. [ABSTRACT FROM AUTHOR]

The repair method 8.3 "Corrosion protection by increasing the electrical resistance" according to EN 1504 (or the repair principle W‐Cl according to the DAfStb directive "Protection and repair of concrete building materials") represents a technically and economically interesting method for the repair of chloride‐contaminated concrete components. The coating applied as part of the repair principle prevents further water absorption of the concrete and, due to its permeability to water vapor, allows the concrete to dehydrate. Over time, this leads to an increase in the electrolytic resistance and thus to a reduction in the rate of corrosion. The article deals with the basic principles underlying this repair principle, deals with the current regulatory situation, and shows the responsibility of the expert planner. Groundbreaking studies on the effectiveness of the repair principle were carried out by Prof. Raupach, to whom this article is dedicated, and are summarized in this paper. The objective of the new studies, which build on the aforementioned research, is to establish universally accepted application limits, for example, the level of the remaining chloride concentration, for the low‐risk use of this repair method. [ABSTRACT FROM AUTHOR]

The repair principle IR – state of knowledge, regulatory consequences, current research While the repair principle IR (increasing resistivity) has become a standard procedure for the repair of carbonation‐induced reinforcement corrosion, its applicability to chloride‐induced reinforcement corrosion is still under discussion. In many cases, IR may display economic advantages at first glance, but its application is linked with an increased risk of failure. This contribution presents the fundamentals of the repair principle IR in case of chloride‐induced corrosion and the current state of knowledge both for uncracked and cracked concrete. Regulatory consequences that arise from the higher failure risk are being discussed. Corrosion monitoring is introduced as a possible means to monitor the performance of the repair measure. Finally, case studies illustrate both the risks of this repair principle and the benefits when applied successfully. [ABSTRACT FROM AUTHOR]

Abstract: New research results for the protection of building components under paving The use of permeable paving for parking areas e.g. is now one of the most common variants in single‐storey underground car parks without ground water or the ground floor of parking garages to avoid the relatively expensive to be coated and reinforced concrete floor slabs as a roadway. If a load‐bearing floor slab is not used, the loads are discharged into the ground via single and strip foundation under the paving slab. Accordingly, the entrained meltwater entrained by cars passes through the permeable pavement to the components lying in the ground. In order to ensure the durability of the reinforced concrete components under the pavement surface in the event of exposure to chloride, the planner must take appropriate measures. The studies presented by the University of Applied Sciences Munich on parking garages show that there can be significant chloride contamination both on the rising components and on the foundations. Furthermore, the permeability of paving coverings scatters strongly. The laboratory studies carried out by a DBV‐sponsored research project show that the coating of reinforced concrete components can be damaged by the installation of the plaster pavement. Furthermore, it was found that not all coating systems defined in accordance with RL‐SIB provide a practical outsourcing that sufficiently protects the reinforced concrete components against corrosion. In the laboratory tests, flexible sealing slurries or OS 5b systems – which have been tested for permanently occurring chloride‐containing water – proved to be most suitable and can be recommended. [ABSTRACT FROM AUTHOR]

Recycling concrete with reinforcement made of basalt fibre polymers: investigations on the composite and tensile load‐bearing behaviour The use of recycling concrete is subject to restrictions in Germany, which prevent its use in environmental conditions containing de‐icing salt of exposure classes XD3 and XS3. To overcome these normative barriers, the Munich UAS is conducting research on the use of alternative reinforcement materials that completely eliminate reinforcement corrosion induced by chlorides. In this regard, non‐corrosive fibre composite bars, made of basalt, are employed, which offer ecological advantages over reinforcements made of stainless steel, glass fibre or carbon. The investigations presented here on the composite and tensile load‐bearing behaviour of basalt fibre‐reinforced polymers have arisen as part of a current research project examining the use of this type of reinforcement in bridge caps made of recycling concrete. In addition to preliminary concrete technology studies on the use of up to 100 % recycled aggregates, composite specimens made of recycled concrete and basalt fibre reinforced polymer were tested to provide insights on the load‐bearing behaviour under static and cyclic conditions. [ABSTRACT FROM AUTHOR]

Load bearing base plates of underground car parks - Aspects in the planning and possibilities for an effective reinforcement design There is a certain insecurity existent among planners of load bearing base plates for underground car parks: on the one hand they try to meet the requirements in regard to water impermeability and durability against chloride exposure by fulfilling strict requirements in regard to maximum crack width and late restraints. This leads to high reinforcement contents of the base plates, as shown in a parameter study. On the other hand the planner is obliged to plan economically. A possible way out of this dilemma is shown in the draft of the DBV fact sheet 'Car Parks' and the watertight guideline: the design principle (EGS) 'planning cracks' allows the reduction of the minimum reinforcement by e. g. targeted placement of crack-inducing elements and reinforcement design. Another discussed aspect of this paper is to verify the tightness against chloride ingress of different concrete mixtures. It is proven that the approach of the standard to ensure the durability by using high strength concrete is not constructive. It is rather to suggest to reduce the strength of the concrete with choosing a suitable binder. [ABSTRACT FROM AUTHOR]

Research of production and maintenance costs for alternative concepts to ensure the durability of parking buildings There is currently an intense discussion about how to ensure the durability of parking buildings. Without having carried out a comprehensive cost analysis for the alternatives for durability concepts costs are nevertheless used as an argument for or against a certain execution. In this publication the costs of various execution concepts are compared on the basis of a virtual two-storey underground garage with standard dimensions for the two major components of 'suspended ceiling' and 'baseplate'. For instance the cost analysis includes the production costs for the minimum reinforcement in dependence of the examined surface protection or of the waterproofing system respectively. Furthermore the costs for maintenance, inspection and repair among other aspects are compared in dependence of the surface protecting system for a service life of 50 years. This cost approach takes into account consists of market fluctuations as well as scheduled maintenance cycles by considering medium, minimum and maximum costs. For the suspended ceiling the following coating or waterproofing systems respectively are examined: surface protection system 'OS 11'; 'mastic asphalt (single/double layer) with asphalt sheeting '; 'mastic asphalt (single/double layer) with surface protection systems OS 10' and 'PMMA' protecting surface system. For the base plate two load cases are investigated: 'water exchange zone' (WW) and 'water pressure' (WD) in combination with the following surface protection systems: 'OS 11', 'mastic asphalt (single/double layer) with asphalt sheeting' and 'OS 8 with accompanying crack treatment'. For the ongoing maintenance costs, engineering values are chosen in accordance to the current state of knowledge. It is expected that current research projects are going to provide scientific results in the near future allowing an update of this cost analysis. [ABSTRACT FROM AUTHOR]

Bei der Planung von Tiefgaragen‐Bodenplatten muss infolge der starken Chlorideinwirkung ein besonderes Augenmerk auf die Dauerhaftigkeit der Konstruktion gelegt werden. Dabei ist auf eine ausreichend hohe Betondeckung mit einem möglichst chloriddichten Beton zu achten, bzw. ein Oberflächenschutzsystem ist aufzubringen. Weiterhin sind Maßnahmen zu ergreifen, dass in Risse keine Chloride eindringen. Diese Prinzipien sind in den vorhandenen Regelwerken vorgegeben. Im Entwurf des neuen DBV‐Merkblattes werden darüber hinausgehend Entwurfsgrundsätze vorgegeben, aus denen sich dann Ausführungsvarianten ableiten lassen. Für die Umsetzung der Entwurfsgrundsätze bei der Ausführung von Tiefgaragen‐Bodenplatten werden drei Beispiele aufgezeigt. From the design principles for RC‐ground slabs in underground car parks to the durable execution Planning of underground floor slabs, special attention must be paid on the durability of the construction as a result of the severe chloride exposure. This durability has to be ensured by a thick concrete cover with a chloride dense concrete or by the application of a surface protection system. Further measures have to be taken to prevent chlorides to penetrate into cracks. These measures are specified within the existing rules and regulations. In the design of new DBV Guide to Good Practise, Design Principles are provided, from which construction alternatives can be derived. For the implementation of the Design Principles at the construction of underground floor slabs three examples are given. [ABSTRACT FROM AUTHOR]

Kathodischer Korrosionsschutz (KKS) von Stahlbetonbauteilen ist gerade bei Parkbauten ein etabliertes Instandsetzungsverfahren. Dabei weist dieses Verfahren gegenüber einer herkömmlichen Instandsetzung (durch Entfernen des chloridbelasteten Betons) einige technische und wirtschaftliche Vorteile, aber auch Nachteile auf, welche bei der Wahl des Instandsetzungskonzeptes zu berücksichtigen sind. KKS ist dabei als “Allgemein anerkannte Regel” der Technik zu werten, auch wenn meist eine Zustimmung im Einzelfall erlangt werden muss. Während es für die Anwendung bei Stahlbetonbauteilen in der Fläche oder an Stützen‐ und Wandfußbereichen zahlreiche Anwendungsbeispiele und Bemessungsregeln gibt, sind häufig besondere Konstruktionselemente oder Detailpunkte vorhanden, die eine Planung und Anwendung von der “Stange” unmöglich machen. Für einige dieser Detailpunkte werden Lösungsmöglichkeiten vorgestellt und diskutiert; u. a. der Schutz der unteren Bewehrungslage bei Trennrissen von Zwischendecken durch Installation des KKS‐Systems auf der Oberseite der Decke. Weiterhin wird vorgestellt, wie Stützen, die statisch stark ausgelastet sind und einen hohen Schädigungsgrad der Bewehrung aufweisen, in einer Kombination aus Bewehrungsergänzung und KKS instand gesetzt werden können. Unzugängliche Bereiche können durch Stabanoden geschützt werden. Abschließend werden die Ausführung geschlitzter Anoden und der Umgang bei Einbauteilen vorgestellt. Repairing of parking structure by using Cathodic Protection – Possible execution of complex points of detail Cathodic Protection (CP) of reinforced concrete members is an established repair method in parking buildings. Compared to a traditional repair (by removal of the chloride‐contaminated concrete) this corrosion protection concept has some technical and economic advantages but also disadvantages, which have to be taken into account at the choice of the repair concept and which also have to be discussed with the client. CP is as generally accepted rule technology, even though an approval in the individual case must be obtained mostly. While there are numerous application examples and rules for the application on the surface of decks or on column and wall feet, special construction elements or points of detail are common in reinforced concrete members making a planning and application “off the peg” impossible. For some of these points of detail solutions are presented and discussed: this is on one hand protecting the rear reinforcement layer of false ceilings with separating cracks by installing the CP‐system on the top of the ceiling. On the other hand is presented as columns with high static loads, which have a high degree of damage of the reinforcement, can be repaired using a combination of reinforcement addition and cathodic protection. Furthermore bar anodes can be used to protect inaccessible places. The CP of metallic installation parts have to be planned with a special attention on a proper current distribution. Here results of a sample are presented. Finally, the application of slotted anodes for the repair of underground car parks are presented. This design allows a CP repair without having to change the component dimension and applying an additional load. [ABSTRACT FROM AUTHOR]

Die Ausführung von unbeschichteten, direkt befahrenen Bodenplatten ist eine nach den aktuellen Normen und Merkblättern anerkannte Bauweise, wenn zum einen ein möglichst chloriddichter Beton bei ausreichend hoher Betondeckung verwendet wird. Zum anderen sollten Maßnahmen ergriffen werden, um die Rissbildung zu vermeiden bzw. sollte eine 'begleitende Rissbehandlung' im Rahmen der Wartung durchgeführt werden. Die Erfahrungen an insgesamt vier durch einen Fachplaner gutachterlich begleiteten Bauvorhaben zeigen, dass sowohl die Chloriddichtheit nachweisbar erreicht werden kann, als auch eine weitestgehende Rissfreiheit, selbst nach mehreren Wintern, eingehalten ist. Entscheidend für den Erfolg der rissfreien Konstruktion ist, dass bereits in den frühen Planungsphasen eine zwängungsarme Auflagerung berücksichtigt wird. Zudem sind auch ein ausreichendes Gefälle sowie die Konzeption von Entwässerungseinrichtungen frühzeitig planerisch zu berücksichtigen. Die Ausführungsqualität der Bodenplatte kann mittels zerstörungsfreier Betondeckungsmessungen und durch Bestimmung der Chloridbelastung überprüft werden. Letztlich konnte mit den hier beschriebenen, unbeschichteten Tiefgaragen-Bodenplatten eine dauerhafte und wirtschaftliche Konstruktion gefunden werden, deren Instandhaltungsaufwand im Vergleich zu beschichteten Bodenplatten deutlich geringer sein wird. Uncoated and directly driven RC-ground slabs in underground car parks - a field report The construction of an uncoated and directly driven RC-ground slab is proven and acknowledged by standards and bulletins, if on one hand a concrete is used, which is chloride dense as possible in combination with a sufficient thick concrete cover. On the other hand actions should be taken to avoid crack initiation or an accompanied crack treatment within the scope of the maintenance should be carried out. The experience of four building projects, which were supervised by concrete technology consultants, show, that as well the chloride impermeability is verifiable achievable as hardly any cracks have been determined - even after several winter periods. Important to achieve a crack-free construction is the consideration of a bearing with reduced restraints already in early stages of the design. Also the planning of a sufficient gradient of the surface and a drainage concept has to be considered early within design. The quality of the execution of the ground slab can be checked by using non destructive concrete cover measurement and by determining the chloride contamination. Finally a durable and cost-effective construction could be achieved with the described uncoated subterranean garage ground slabs leading to a reduced maintenance expense compared to coated ground slabs. [ABSTRACT FROM AUTHOR]

Corrosion monitoring of reinforced or prestressed concrete structures has become increasingly important in recent years. Areas of application include components that are no longer accessible after completion or where potential field measurements cannot be carried out due to existing coatings. Corrosion monitoring can also be used to monitor the progress of corrosion in corroding systems, e.g. to prove the success of repair measures according to repair principle 8 in accordance with EN 1504‐9 or repair method 8.3 in accordance with the DIBt repair guideline. It also could be used to prove the functionality of cathodic corrosion protection systems in accordance with ISO 12696. Despite the increasing importance of corrosion monitoring, no guidelines or recommendations existed until 2018. This gap was closed by the English version of specification B12, "Corrosion Monitoring of Reinforced and Prestressed Concrete Structures," of the German Society for Non‐Destructive Testing, which was published in 2021. This article introduces specification B12 by explaining the basic measurement principles and illustrating the potential of corrosion monitoring in new and existing buildings. [ABSTRACT FROM AUTHOR]

Repair of car park ceilings with cathodic corrosion protection: investigations on the cathodic protection with separation cracks A repair of parking structures according to the repair principle of the cathodic corrosion protection (CP) can be an economic and gentle possibility to sustainably increase the remaining service life of the structure. RC ceilings frequently show separation cracks with penetrating chloride‐containing water and pitting corrosion of the reinforcement on the underside of the ceiling. This raises the question for the expert planner whether a CP system applied to the upper side of the ceiling can safely protect the corroding reinforcement on the underside. In practice it has been shown that proof of sufficient protection for this application is not trivial. This question was thoroughly examined in laboratory tests at the Institute for Material and Building Research of Munich University of Applied Sciences and in an underground parking garage. In summary of the investigations, it can be shown that the proof of the protection of the rear reinforcement in the separation crack can only be provided in a few of the investigated cases with the CP‐system installed solely on the upper ceiling side. The 100 mV criterion stipulated normatively in DIN EN ISO 12696 is too conservative for the proof of protection. However, if the proof of the 100 mV criterion is not successful, then corrosion and protective current measurements on subsequently electrically separated reinforcement areas can be considered more suitable for the proof of protection. [ABSTRACT FROM AUTHOR]

Influence of chloride induced pitting corrosion on the mechanical properties of reinforcing bars The durability of chloride‐exposed reinforced concrete components is mainly determined by the corrosion behavior of the reinforcing steel. If an ingress of chlorides in chritical concentration into the component has taken place, pitting corrosion can appear. The occurring, very local loss of material can lead to high cross‐sectional losses of the reinforcement in a short time. For repair planning the planner is faced with the task of specifying the type and scope of the rehabilitation. In doing so, the challenge is to determine the present cross‐sectional losses as accurate as possible. However, an exact determination of the cross‐sectional loss on the site is difficult because of the geometry of the pitting. This is why the loss of cross‐section is often estimated visually. Furthermore, the question arises whether the pittings produce notch stresses that have an influence on the load‐bearing capacity and lead to deviating strength values in comparison to a simple cross‐sectional analysis. In addition, the question of the influence on local damage on the strain behavior of the reinforcing steel is to be answered. To improve the evaluation of damaged reinforcement due to pitting corrosion, tests on reinforcing steel bars with a wide spectrum of damage due to chloride‐induced corrosion have been carried out at the Munich University of Applied Sciences. For this purpose, rebar probes of various diameters were taken both from an underground parking garage of the 1960s, as well as artificial corroded samples produced in the laboratory. The steel samples were examined on the basis of their optical appearance, the measured residual cross section, as well as the residual strain behavior and the residual static load capacity. [ABSTRACT FROM AUTHOR]

The critical chloride content Ccrit is an indicator of the corrosion resistance of reinforcing steels in concrete. In this article, several experimental methods for determining the critical chloride content Ccrit of mild and alloyed (12% Cr) steel in cementitious materials are compared. The methods used include accelerated polarization tests and tests employing more natural (unpolarized) conditions in which chloride ingress occurs by diffusion and capillary uptake. The advantages and disadvantages of the methods are discussed, in particular, against the objective of reaching a compromise between applicability to practice and feasibility in laboratory testing. [ABSTRACT FROM AUTHOR]

The critical chloride content Ccrit is an indicator of the corrosion resistance of reinforcing steels in concrete. In this article, several experimental methods for determining the critical chloride content Ccrit of mild and alloyed (12% Cr) steel in cementitious materials are compared. The methods used include accelerated polarization tests and tests employing more natural (unpolarized) conditions in which chloride ingress occurs by diffusion and capillary uptake. The advantages and disadvantages of the methods are discussed, in particular, against the objective of reaching a compromise between applicability to practice and feasibility in laboratory testing. [ABSTRACT FROM AUTHOR]

The critical chloride content Ccrit is an indicator for the corrosion resistance of reinforcing steels in concrete. In this article, several experimental methods for determining the critical chloride content Ccrit of mild and an alloyed (12% Cr) steel in cementitious materials are compared. The methods used include accelerated polarization tests and tests using more natural (unpolarized) conditions in which chloride ingress occurs by diffusion and capillary uptake. The advantages and disadvantages of the methods are discussed, in particular, with the objective of reaching a compromise between applicability to practice and feasibility in laboratory testing. [ABSTRACT FROM AUTHOR]

Investigation on tension and bonding behaviour of basalt fibre reinforced polymers in concrete structures For retrofitting of RC structures, the concrete cover of the renewed reinforcement has to be sufficient to ensure the durability. Alternative reinforcement like rebars of basalt fibre reinforced polymers (BFRP) gives the possibility to minimize the concrete cover ensuring durable structures due to their resistance against carbonation and chlorides. In this paper investigations on load‐bearing behaviour of BFRP reinforced test specimens as an excerpt from a research project on basalt fibre reinforced concrete as repairing material with shotcrete and also basalt rebars as additional strengthening reinforcement for fair faced concrete facades are presented. The tested BFRP rebars show higher tension strength and lower Young's Modulus as comparable steel reinforcement bars. In centrical tension tests on the BFRP reinforced concrete specimen longitudinal cracking due to high tension in the contact zone and a higher number and also higher widths of crosswise cracking appear. The load bearing behaviour can be confirmed by numerical simulation. The results of the investigation with the incident light microscope on prepared specimen after tension tests show an enhanced number of microcracks in the contact zone between BFRP rebar and cement matrix. In pull out tests always the concrete failed, never the BFRP rebars. The results of this investigation confirm the possibility to ensure durable concrete structures using BFRP reinforcement. Further tests have been carried out on the flexural strength behaviour, the fatigue strength and durability. At the moment BFRP rebars of various designs are tested. [ABSTRACT FROM AUTHOR]

Abstract: Corrosion Monitoring of Reinforced Concrete Structures – DGZfP Specification B12 During the last few years corrosion monitoring of reinforced or prestressed concrete structures has developed into a valuable tool to assist with the assessment of existing structures. Besides obvious applications as for instance structural elements which are not accessible after completion or which cannot be assessed by means of half‐cell potential measurement due to existing coatings, corrosion monitoring can also be very beneficial for the monitoring of the corrosion progress of corroding systems. This has gained increasing relevance e.g. for the monitoring of repair measures according to repair principle “increasing resistivity” or for the surveillance of Cathodic Protection installations (CP). Despite this increasing relevance there are up to now no guidelines or standards for corrosion monitoring in Germany. This gap shall now be bridged by the new specification B12 “Corrosion Monitoring of Reinforced and Prestressed Concrete Structures” published by the German Society for Non‐Destructive Testing DGZfP in spring 2018 [1]. This article will briefly present the specification B12, highlight the basic measurement principles and illustrate the potentials of corrosion monitoring for new and existing structures by means of case studies. [ABSTRACT FROM AUTHOR]