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This paper investigates the performance of pre‐tensioned tendons deliberately exposed to higher than normal impressed current cathodic protection (ICCP) to replicate accidental over‐polarisation. Plain ungalvanised tendons, 5.4 mm O, were pre‐stressed in moulds and cast in mortar. Two levels of pre‐tensioning were investigated, low (~30% ultimate tensile strength [UTS]) and high level (~80% UTS). Three different degrees of corrosion with target losses of cross‐sectional area of 0%–1%, 2%–4% and 4%–7%, respectively, were employed to replicate in situ conditions. ICCP was applied to the tendons at two levels of polarisation, normal protection (ICCP‐N) in the range of −650 to −750 mV and overprotection (ICCP‐O) ranging between −850 and −1300 mV, both versus Ag/AgCI/0.5‐M KCI for an extended period. After ICCP, the tendons were removed from the mortar and slow strain tensile tests were conducted. The results show that ICCP at both normal and overprotection had no significant influence on the elastic modulus, yield, 0.2% proof stress and ultimate strength of the tested tendons. Although ductility was reduced, fracture occurred after reaching the ultimate strength.

The influence of the long term effects of impressed current cathodic protection (ICCP) on the bond strength is investigated. A total of 16 pull-out specimens were divided into four series and the steel bars pre-corroded to target degrees of 0 % (control), 1 %, 2 % and 5 % weight loss. Four levels of ICCP current density ranging from approximately 0 (control) to over 1000 µA/cm2 were applied to each series. These are considerably higher than the levels typically used in practice, which rarely exceed 2 µA/cm2, but were used to replicate long term application within a reasonable timescale. Following pull-out tests, the values of bond load were determined. The analysis accounts for the accelerated ICCP by relating the total charge to the steel reinforcement in coulombs (current x time) to the bond values and migration of chloride ions. The results show that although some loss in bond is evident from the ICCP, an optimised current density can be applied to a real structure without affecting the as-designed bond strength in the long term e.g. ≤ 0.65 µA/cm2 for an ICCP duration of 70 years. Application of the same current density reduces the chloride concentration from around the steel irrespective of the degree of corrosion.

Circular concrete tanks and containment bunds constructed by the pre-load method involves pre-stressing the concrete by repeatedly wrapping layers of highly tensioned tendons. Each layer is covered with gunite. Corrosion may lead to rupture and an explosive type failure is avoided if the gunite is able to absorb the transfer stress. Zinc galvanizing is used to increase the tendons resistance to corrosion but its smoothness can influence bond characteristics, as can corrosion if extensive. This paper investigates the pre-stress transfer of ruptured pre-load tendons in gunite, both in the uncorroded and corroded state. Laboratory testing was conducted where tendons were pre-loaded in custom-built stressing moulds (to 1000 MPa) and simulated gunite applied. Different degrees of accelerated corrosion were applied to the tendons (0–10%). The bond stress at transfer was determined by measuring the contraction of the tendon during release of the pre-stress (replicating a broken tendon). The results show that a low bond stress was found either as a result of the smooth zinc coating (uncorroded tendons) or due to higher levels of corrosion. These results were compared to design equations from Eurocode 2 and recommendations are made for reducing the bond coefficient $$ \upeta_{p1} $$ , the coefficient that takes into account the type of tendon and the bond situation. Analysis is subsequently conducted to determine the transfer stress in the gunite by modelling single and double tendon ruptures and establishing the magnitude of compressive stress which, if excessive, may lead to an explosive type failure of the gunite.

Cathodic protection (CP) has been successfully employed to protect steel-framed masonry buildings from corrosion related damage. When a CP system is installed to protect the structural members, other metallic items which are within the fabric of the structure but are not in direct electrical continuity may suffer from stray current interactions, resulting in accelerated corrosion of the discontinuous items. Therefore, these must be considered when CP systems are designed prior to installation. This paper presents both experimental and numerical studies into the risk and extent of stray current corrosion in steel-framed masonry structures when subject to impressed current cathodic protection. The objective is to allow CP systems to be optimised so that interference is minimised without compromising the technical or cost benefits of this method of corrosion control.

The present paper presents the influence of resistivity on the current and potential distribution of cathodic protection (CP) systems for steel framed masonry structures. The work involves both experimental measurements and boundary element analysis and follows on from earlier experiments employing sand as a simple model for masonry encasement that has been reported elsewhere. Factors such as the size and type of masonry, moisture content and width of mortar joints will affect the resistance of the path through which the CP currents pass and thereby influence the distribution onto the steel surface. To represent such variations in resistance, it has been necessary to construct a small scale specimen replicating, as far as possible, actual applications on steel framed structures. The results from the laboratory specimen and numerical modelling are in sufficient agreement to confirm the validity of the modelling approach and allow the results to be employed for the purposes of design and development.

Reinforced concrete beams are normally designed as under-reinforced to provide ductile behaviour i.e. the tensile moment of resistance, M t(0) is less than the moment of resistance of the compressive zone, M c . The degree of under-reinforcement (M t(0)/M c ratio) can depend upon the preferences of the designer in complying with design and construction constraints, codes and availability of steel reinforcement diameters and length. M t(0)/M c is further influenced during service life by corrosion which decreases M t(0). The paper investigates the influence of M t(0)/M c on the residual flexural strength of corroded beams and determines detailing parameters (e.g. size and percentage of steel reinforcement, cover) on M t(0)/M c . Corroded reinforced concrete beams (100 mm × 150 mm deep) with varying M t(0)/M c ratios were tested in flexure. The results of the investigation were combined with the results of similar work by other researchers and show that beams with lower M t(0)/M c ratios suffer lower flexural strength loss when subjected to tensile reinforcement corrosion. Cover to the main steel does not directly influence M t(0)/M c and, thus, the residual flexural strength of corroded beams is not normally affected by increased cover. A simplified expression for estimating the residual strength of corroded beams is also given.

Guidance for highway bridge and structure maintenance management in the UK is provided by the code of practice (CoP) 'Management of Highway Structures'. With regards to inspection of reinforced concrete beams in accordance with the code, the professional judgement of the bridge engineer is required to assess the extent and severity of deterioration with help from a library of different defects. The Extent of the defects is rated A – E whilst the Severity is scored 1 – 5, giving an Extent and Severity score for each element, known as the element condition score. However, the Code does not provide information on the corresponding levels of corrosion in the steel reinforcement in the damaged beam. The purpose of this paper is to relate the element severity scores for a range of damaged reinforced concrete beams to approximate levels of corrosion of the main steel, thereby giving the bridge inspector an understanding of the seriousness of corrosion for each of the five Severity scores.

A novel technique has been proposed and researched in which carbon fibre reinforced polymers (CFRP) are employed to provide both structural strengthening and electrochemical corrosion protection to reinforced concrete (RC) elements suffering from corrosion related damage. CFRPs fabric or rod was used for both flexural strengthening of pre-corroded reinforced concrete beams and operated in a dual functional capacity as an impressed current cathodic protection (ICCP) anode. After a period of ICCP operation at high current density (>64mA/m2 of steel surface area for rod and >128mA/m2 of steel surface area for fabric), the beams were subjected to flexural testing to determine the load-deflection relationship. The potential decays of the steel met recognised ICCP standards and the CFRP remained effective in strengthening the corroded reinforced concrete beams. The ultimate strength of the dual function CFRPs reduced slightly when compared with control reinforced specimens used for strengthening only. This is attributed to the application of the ICCP at high current densities influencing the bond at the concrete/CFRP interface. A number of methods for maintaining and enhancing bond are presently being investigated, together with the optimisation of current densities for operating the CFRP anodes

Cathodic protection has been proven to be one of the most widely applicable and cost-effective solutions for tackling steel corrosion in reinforced concrete. In this study, the possible use of carbon fibre composites, which are primarily used to strengthen concrete members, has been investigated as impressed current cathodic protection anodes. Carbon fibre anodes have been assessed in both concrete and calcium hydroxide solution. Two bonding mediums incorporating epoxy and geopolymer have also been investigated. The results demonstrate that epoxy resin can be used for bonding carbon fibre fabric anodes to reinforced concrete structures while geopolymer is more effective for bonding carbon fibre reinforced polymer (CFRP) rod into preformed grooves in the concrete surface. The dissolution of carbon fibre anode appears to stablise after a period of time, dependent upon the size and shape of the anode and applied voltage and current. Based on the present results, a maximum current density of 128 mA/m2 of reinforcing steel area is recommended for the operation of CFRP fabric anode and 64 mA/m2 of reinforcing steel area for that of CFRP rod anode.

Many high-profile steel-framed masonry buildings are susceptible to extensive damage as a result of corrosion of the steel frame. This has resulted in serious consequences with respect to serviceability, safety, aesthetics and heritage. Cathodic protection (CP) is a proven method for preventing and protecting buried and submerged steel and reinforced concrete structures from corrosion. More recently, the method has been introduced to prevent and control corrosion in steel-framed masonry structures. However, despite several sizeable CP installations around the world, there are no formal guidelines for the design, installation and operation of such systems and much of the\ud knowledge is based on empirical observations. This paper presents both experimental and numerical studies on the cathodic protection of representative steel framed masonry structures. These studies are considered essential in the understanding of the mechanisms of cathodic protection and the design of optimised cathodic protection systems for such structures.