Cover zone properties influencing acoustic emission due to corrosion

The deterioration of reinforced concrete is a serviceability problem world-wide. The cover zone plays an important role in the durability and serviceability of concrete and provides the initial barrier to aggressive species. The research presented investigates the potential of acoustic emission (AE) as a means of identifying corrosion at an early stage, before any significant cover damage has occurred. The purpose of part of the study was to identify the influential cover zone factors that affect the magnitude of the acoustic emission measurements per gram of steel loss. Prisms with various combinations of strength, cover thickness, aggregate and rebar diameters were studied to ascertain the important variables likely to be encountered on reinforced structures. The experimental results confirmed that early corrosion, verified by internal visual inspection and mass loss, can be detected by AE and before any external signs of cracking. They also show that the most influential parameter affecting the AE measurement is concrete strength, being exponentially related to the AE Energy. Material properties such as cover thickness had a negligible effect on AE Energy during the initial stages of reinforcement corrosion, whereas from this initial work, the rebar diameter indicated a promising relationship with AE Energy per gram of steel loss

Condition monitoring of reinforced concrete structures at risk from reinforcement corrosion

The corrosion of reinforced concrete structures is a major issue in the UK and worldwide, both structurally and from a maintenance management aspect. Damage induced by the corrosion of the steel can dramatically reduce the designed service life of the structure through loss of bond between the steel and concrete, or from localised loss of section of the corroding rebars. Failure to manage the maintenance of reinforced concrete may result in the premature replacement of the structure or in extreme cases, structural failure. Avoiding such scenarios can be aided through improved detection and monitoring of corrosion in concrete. In addition, combining this with a condition management tool, capable of benchmarking, index testing and prioritising areas of the concrete structure(s) for remedial action, would provide robust facilities management techniques for structural assets. This paper suggests how the results of a novel non-destructive corrosion detection technique, currently being developed, could be incorporated into a condition-monitoring tool for the facilities management of structures. The development of protocols based on laboratory and field data enable the formation of a condition-monitoring tool forming part of a longterm maintenance strategy for estate owners and managers

Influence of diurnal and seasonal temperature variations on the detection of corrosion in reinforced concrete by acoustic emission

Chloride rich reinforced concrete prisms were coupled to chloride free prisms and exposed to diurnal and seasonal temperature cycles typical of those found in the UK. Acoustic Emissions (AE) and galvanic currents were continuously monitored and correlated with ambient temperature. AE and galvanic currents were found to emulate the evolution of temperature in the diurnal cycles, although no specific relationship between AE and galvanic current could be obtained. The influence of seasonal variations in galvanic current had no obvious influence on AE Energy per second over the range of corrosion rates studied. The findings suggest that AE is more sensitive to short term (diurnal) changes in corrosion rates than the longer (seasonal) effects. It was hypothesised that this is due to transitory changes in the internal microclimate of the concrete

Electrochemical behaviour of steel reinforced concrete during accelerated corrosion testing

Corrosion of reinforcing steel presents a major durability issue worldwide and is the focus of much research activity. The long time periods involved in replicating reinforcement corrosion within laboratories has resulted in a number of accelerated test methods being developed. The basis of this research presented in this paper was to examine the impressed current technique often used to induce reinforcement corrosion. The suitability of the technique to model chloride induced corrosion was investigated by examining the electrochemical nature of the test method. Corrosion was induced in prisms of differing characteristic strengths and cover thicknesses by applying a current for between 3 and 17 days. The gravimetrical and theoretical mass losses are compared and a modified expression based on Faraday’s law relating the electrical current to the mass loss is also proposed which accounts for the localised nature of chloride-induced corrosion. It was found that the technique is a suitable method to simulate reinforcement corrosion

Risk-based investigation of steel reinforcement corrosion using the AeCORR technique

The use of a non-destructive acoustic evaluation technique as a Risk Based Inspection tool to detect the corrosion of steel reinforcement in concrete is presented in this paper. It offers the potential to save time and money for facilities owners and users. Recent research has demonstrated that AE has the ability to identify corrosion activity in concrete before conventional NDT methods, enabling faster intervention and increasing the repair options available. Monitoring a structure using the AeCORR technique, currently being researched and under development in the field, can create a digital map of part of a structure enabling an unbiased reference point for that structure for future maintenance tests as well as being able to distinguish areas of active corrosion. This paper reviews the principles and development of the new AeCORR technique for detecting and estimating the scale of corrosion induced damage and its ability as a tool to index test parts of structures

Determining the corrosion state of steel reinforcement in concrete

The corrosion of reinforced concrete structures is a major issue in the UK and worldwide from both a structural view and maintenance management aspect. Early detection of this degradation process will provide the owner with the optimum number of repair options whilst minimising repair costs. This paper reports on the new non-destructive corrosion detection technique for reinforced concrete – AeCORR, specifically targeted towards detecting active corrosion damage occurring within the concrete during the very early stages of the degradation process. An overview of the technique is provided together with a recent case study

Regional cerebral oxygenation monitoring - intraoperative management in a patient with severe left ventricular dysfunction

Intraoperative near-infrared spectroscopy cerebral oxygenation monitoring assists intraoperative decision-making in environments without extracorporeal membrane oxygenation (ECMO), left ventricular assist device (LVAD) or access to cardiac transplantation. We report a case of an anomalous left coronary artery arising from the pulmonary artery (ALCAPA), undergoing cardiac surgery. A 4-month-old infant presented in extremis with cardiac failure. We discuss the pathophysiology and challenging intraoperative management of ALCAPA with extensive ischaemia and myocardial infarction

The influence of impact-based severe weather warnings on risk perceptions and intended protective actions

This paper presents the results of an online survey of the New Zealand public (n = 1364), conducted in 2015, that tested the influence of impact-based severe weather warnings on risk perceptions and intended protective actions. We used a hypothetical severe weather event involving strong winds, with 50% of participants receiving an impact-based warning, and 50% receiving a more traditional phenomenon-based warning (which in this case is when the wind speed is expected to be higher than a given number). Our results indicate that impact-based warnings may be more effective than phenomenon-based warnings in influencing the recipient's perception of the hazardous event (their sense of threat, concern, and understanding of the potential impacts), but this does not translate to a higher level of action. Characteristics of gender, age, and location of residence were also influences on risk perceptions and intended actions. However, experience with having been affected by strong winds in the past was not a strong influence on intending to respond. Our findings support the inclusion of information about hazards, impacts, and ‘what to do’ information in a warning message

Soluble α2-macroglobulin receptor is increased in endotracheal aspirates from infants and children after cardiopulmonary bypass

ObjectiveCytokine dysregulation contributes to the systemic inflammatory response after cardiopulmonary bypass. Clearance of cytokine binding proteins may be important in the resolution of inflammation. Our aim was to determine whether the cytokine binding protein α2-macroglobulin and its soluble receptor were upregulated in endotracheal aspirates from infants and children undergoing cardiopulmonary bypass.MethodsSeventy tracheal aspirates were collected before and after cardiopulmonary bypass from 35 infants and children undergoing surgical correction of congenital heart defects. α2-Macroglobulin and the soluble α2-macroglobulin receptor were identified by Western blot. With the use of multi-analyte cytokine profiling, pro-inflammatory and anti-inflammatory cytokines were quantified, normalized to total protein, and expressed as ratios. Paired t tests and Wilcoxon signed-rank tests were performed between prebypass and postbypass samples. Correlations were examined among α2-macroglobulin, soluble α2-macroglobulin receptor, cytokine ratios, and the clinical variables of cardiopulmonary bypass, aortic crossclamp, and circulatory arrest times.Resultsα2-Macroglobulin increased by 50% (mean densitometry increase 82,683 ± 184,594, P = .012), and soluble α2-macroglobulin receptor increased by 17% (mean densitometry increase 506,148 ± 687,037, P = .0001) after cardiopulmonary bypass. The ratio of interleukin-8/interleukin-4 increased by 136% (P = .0001), and interleukin-8/interleukin-10 increased by 102% (P = .001). The increase in soluble α2-macroglobulin receptor was positively correlated with the ratios of interleukin-8/interleukin-4 and interleukin-8/interleukin-10. There were no statistically significant positive correlations between the increase in α2-macroglobulin or soluble α2-macroglobulin receptor and measured clinical variables.ConclusionsWe report for the first time the upregulation of α2-macroglobulin and soluble α2-macroglobulin receptor in tracheal aspirates after cardiopulmonary bypass in infants and children. Soluble α2-macroglobulin receptor correlates with increased α2-macroglobulin and a disproportionate increase in pro-inflammatory to anti-inflammatory cytokine ratios

Alkaline Phosphatase Treatment of Acute Kidney Injury in an Infant Piglet Model of Cardiopulmonary Bypass with Deep Hypothermic Circulatory Arrest

Acute kidney injury (AKI) is associated with prolonged hospitalization and mortality following infant cardiac surgery, but therapeutic options are limited. Alkaline phosphatase (AP) infusion reduced AKI in phase 2 sepsis trials but has not been evaluated for cardiac surgery-induced AKI. We developed a porcine model of infant cardiopulmonary bypass (CPB) with deep hypothermic circulatory arrest (DHCA) to investigate post-CPB/DHCA AKI, measure serum/renal tissue AP activity with escalating doses of AP infusion, and provide preliminary assessment of AP infusion for prevention of AKI. Infant pigs underwent CPB with DHCA followed by survival for 4 h. Groups were treated with escalating doses of bovine intestinal AP (1, 5, or 25U/kg/hr). Anesthesia controls were mechanically ventilated for 7 h without CPB. CPB/DHCA animals demonstrated histologic and biomarker evidence of AKI as well as decreased serum and renal tissue AP compared to anesthesia controls. Only high dose AP infusion significantly increased serum or renal tissue AP activity. Preliminary efficacy evaluation demonstrated a trend towards decreased AKI in the high dose AP group. The results of this dose-finding study indicate that AP infusion at the dose of 25U/kg/hr corrects serum and tissue AP deficiency and may prevent AKI in this piglet model of infant CPB/DHCA