Long‑term phase changes in cathodically protected marine reinforced concrete bridge

The application of cathodic protection (CP) gains increasing interest for maintaining the structural integrity of coastal concrete bridges facing premature degradation due to reinforcement corrosion. The present investigation was undertaken to obtain field experience on the long-term performance of impressed current cathodic protection (ICCP) installed on a Norwegian marine concrete bridge. Cores with and without anode ribbons from five protection zones were extracted 16–17 years after installation of ICCP. The cores were investigated by visual inspection and using µ-XRF for elemental distribution. µ-XRF measurements showed decreased intensities for calcium and sulfur around anode ribbons in some samples. Chloride accumulation at anode ribbons was observed in three of five cores, leading to lower ingress depth in the concrete but also a higher maximum chloride content near the anode compared to the cores without anode ribbons. The anode ribbons appeared intact. Phase changes around the anode ribbon were investigated with XRD, TGA and pH measurement. The ICCP had induced neutralization (pH 7) of the overlay mortar in the vicinity of some of the anode ribbons, resulting in the decomposition of hydration products like portlandite and the formation of gypsum, leading to a weaker material

Service life and life cycle cost modelling of cathodic protection systems for concrete structures

Cathodic protection (CP) of reinforcing steel has been applied successfully to concrete structures with corrosion damage for more than 25 years. Performance and maintenance data are reported from an inventory of CP systems in The Netherlands installed on about 100 structures between 1987 and 2010. The large majority provides corrosion protection for a long time. Degradation of components and overall systems seems to occur in limited numbers. Failure of components and total systems as a function of age is quantified. On the average, the time until minor repairs of parts is necessary is about 15 years. Global failure of the anode, which necessitates near complete replacement of the system, is rare. Based on the statistical analysis of field data, the cost of maintaining a CP system is predicted using a life cycle cost model

The steel–concrete interface

Although the steel–concrete interface (SCI) is widely recognized to influence the durability of reinforced concrete, a systematic overview and detailed documentation of the various aspects of the SCI are lacking. In this paper, we compiled a comprehensive list of possible local characteristics at the SCI and reviewed available information regarding their properties as well as their occurrence in engineering structures and in the laboratory. Given the complexity of the SCI, we suggested a systematic approach to describe it in terms of local characteristics and their physical and chemical properties. It was found that the SCI exhibits significant spatial inhomogeneity along and around as well as perpendicular to the reinforcing steel. The SCI can differ strongly between different engineering structures and also between different members within a structure; particular differences are expected between structures built before and after the 1970/1980s. A single SCI representing all on-site conditions does not exist. Additionally, SCIs in common laboratory-made specimens exhibit significant differences compared to engineering structures. Thus, results from laboratory studies and from practical experience should be applied to engineering structures with caution. Finally, recommendations for further research are made

Kloridmotstand for mørtler med slaggsement : Varige konstruksjoner 2012-2015

Denne rapporten tilhører Prosjekt 3: Fremtidens bruer. Prosjektet skal bidra til at fremtidige bruer bygges med materialer bedre tilpasset det miljøet konstruksjonene skal stå i. Prosjektet skal bygge på etablert kunnskap om skadeutvikling og de sårbare punktene som identifiseres i Prosjekt 1: Tilstandsutvikling bruer, og skal omhandle både materialer, utførelse og kontroll. Prosjektet skal resultere i at fremtidige bruer oppnår forutsatt levetid med reduserte og mer forutsigbare drift- og vedlikeholdskostnader.Et eksperimentelt program ble gjennomført for å studere egenskaper til fem mørtelblandinger med: CEM III / B (to typer); en CEM III / A (med 50% slagg) med silikastøv ; og en CEM I og en CEM II / A-V (flygeaskesement), begge med silikastøv. Rapid Chloride Migration (RCM) og elektrisk motstand ble testet i aldere mellom to dager og ett år. RCM- verdier viste konsistent nedgang og resistivitet viste økning mellom to dager og ett år. Forsøkene vil pågå i 3 år. Hensikten er å gi et bedre grunnlag til å vurdere bruk av slaggsementer i Norge som et virkemiddel for å oppnå mer bestandige betongkonstruksjoner. Rapporten inneholder data opp til 1 år. Varige konstruksjoner består, i tillegg til et overordnet implementeringsprosjekt, av fire prosjekter: Prosjekt 1: Tilstandsutvikling bruer Prosjekt 2: Tilstandsutvikling tunneler Prosjekt 3: Fremtidens bruer Prosjekt 4: Fremtidens tunnelerStatens vegvesen Vegdirektorate

Cathodic protection of reinforcement in concrete – experience and development over 30 years

This paper presents developments over 30 years in the field of cathodic protection of steel reinforcement in concrete in The Netherlands and elsewhere. From the late 1980s major developments have been: application to large numbers of precast elements corroding due to mixed-in chloride with drilled in titanium anodes and conductive coatings; analysis of working life of systems and components and end-of-life considerations; application to prestressed structures; new anode types including galvanic systems with associated life and design considerations; numerical modelling and preventative applications. Presently, CP has become a fully accepted method of securing safety and serviceability of buildings and infrastructure. Major successes and lessons learned will be presented. Technical and non-technical developments are highlighted and some recent innovative CP systems are discussed

Cathodic protection of reinforcement in concrete – experience and development over 30 years

This paper presents developments over 30 years in the field of cathodic protection of steel reinforcement in concrete in The Netherlands and elsewhere. From the late 1980s major developments have been: application to large numbers of precast elements corroding due to mixed-in chloride with drilled in titanium anodes and conductive coatings; analysis of working life of systems and components and end-of-life considerations; application to prestressed structures; new anode types including galvanic systems with associated life and design considerations; numerical modelling and preventative applications. Presently, CP has become a fully accepted method of securing safety and serviceability of buildings and infrastructure. Major successes and lessons learned will be presented. Technical and non-technical developments are highlighted and some recent innovative CP systems are discussed.</jats:p

Cathodic protection of steel in concrete – experience and overview of 30 years application

This paper presents an overview of 30 years' experience with cathodic protection of steel in concrete in The Netherlands. Principles and practical aspects of CP and its design and installation are presented. Three phases have passed from the late 1980s until present: pioneering, development and maturity. In the first period CP was mainly applied to precast elements corroding due to mixedin chlorides. The parties involved worked together to draw up a Technical Guideline. In the second period, application to bridges came up, including post-tensioned structures, which was then innovative. Furthermore, galvanic anode systems were introduced. In the third period, CP became a fully accepted method of securing durability and safety. Renewed collaboration led to a database that allowed analysis of various aspects of CP system working life, including shortcomings in early systems. Major successes and lessons learned will be presented. Technical and non-technical developments are highlighted and some recent innovative CP components and systems are discussed

Forensic Investigation Concerning Inspection and Diagnosis of Condition of Water Storage Systems in the Gulf

Sandberg were asked to visit and comment on a sizeable project in the Gulf involving water storage towers, ground reservoirs and ancillary buildings in contemplation of legal proceedings. The structures had been built by a contractor but some problems had occurred in construction due to the high temperatures and issues with the concrete placement. The main issue that needed to be resolved was whether the problems that occurred were within acceptable limits for that type of construction and what repair recommendations were appropriate. The Client for the project had rejected the structures and was aiming for demolition and reconstruction which was a draconian step, given the level of problems – all of which were easily repairable. A significant amount of misdiagnosis had occurred with dark flecks on the surface of reservoirs being attributed to corrosion of reinforcement, for example, when in fact they were due to mould growth on the surface of the concrete and were literally surface deep only. There were also significant questions to be answered as to what constituted an acceptable level of leakage from water storage towers. An issue was also present with very severe corrosion to some reinforcing bars close to ground level in several ground reservoirs, despite the reinforcement being epoxy coated. It was considered highly likely that this damage was in fact due to stray current corrosion from current leakage from the cathodically protected water pipelines that delivered water to the facilities in question.This paper will discuss the inspection and diagnosis of the problems and the feasibility and need for appropriate repairs