Jesé Mangual

Corrosion Damage Quantification of Prestressing Strands Using Acoustic Emission

AbstractSteel degradation due to corrosion in prestressed concrete bridges has been of major concern as it presents a threat to the integrity of structures adjacent to marine environments or where deicing salts are regularly used. To assess the potential for monitoring of the corrosion process, an accelerated corrosion testing program has been conducted. A series of specimens with dimensions 114×114×508  mm (4.5×4.5×20  in.) were subjected to constant potential application through the embedded steel strand while being continuously monitored with acoustic emission (AE). Depassivation of the strand was detected by monitoring the fluctuations in applied anodic current. Half-cell potential measurements assessed the probability of corrosion, and all results obtained were compared to acoustic emission data. The mass loss of the corroded strands was correlated to acoustic emission intensity analysis to quantify the degree of damage. Results show that acoustic emission is as sensitive as half-cell potential for d...

Acoustic-Emission-Based Characterization of Corrosion Damage in Cracked Concrete with Prestressing Strand

An accelerated corrosion study to assess the feasibility of acoustic emission (AE) for the detection of active corrosion in prestressing strand is described. Concrete prisms with an embedded steel strand were corroded by supplying a constant potential between the strand and a copper plate while the specimens were immersed in a 3% sodium chloride (NaCl) solution. Corrosion was detected using the half-cell potential (HCP), steel section loss, and visual inspection, and the results were compared to AE data. The location of active corrosion was determined experimentally based on the characteristic wave speed. An intensity analysis approach was used to plot the relative significance of the corrosion damage and a classification chart is presented. Results indicate that AE is a useful, nonintrusive technique for the detection and quantification of corrosion damage and may be developed as a structural prognostic tool for maintenance prioritization.

Assessing Corrosion Damage in Post-Tensioned Concrete Structures Using Acoustic Emission

AbstractThe ingress of chlorides into posttensioned (PT) concrete structures is a leading cause of corrosion of the prestressing strands. This reduces the strength, durability, and service life of the structure and may result in catastrophic failure. A structural health monitoring (SHM) method is needed to improve the maintenance procedures associated with this method of construction. To evaluate the potential of acoustic emission monitoring for this application, long term corrosion monitoring tests were performed on specimens that were representative of internal and external posttensioning methods. Corrosion was induced in the specimens by adding chlorides to the grout and by performing wet/dry cycling with NaCl solution. The corrosion process was monitored by half-cell potential measurements (HCP) and acoustic emission (AE). Results show that AE has the ability to detect corrosion damage in the PT specimens with similar accuracy to HCP measurements. Furthermore, intensity analysis of the AE data shows t...

Assessment of corrosion rate in prestressed concrete with acoustic emission

Acoustic Emission (AE) sensing was employed to assess the rate of corrosion of steel strands in small scale concrete block specimens. The corrosion process was accelerated in a laboratory environment using a potentiostat to supply a constant potential difference with a 3% NaCl solution as the electrolyte. The embedded prestressing steel strand served as the anode, and a copper plate served as the cathode. Corrosion rate, half-cell potential measurements, and AE activity were recorded continuously throughout each test and examined to assess the development of corrosion and its rate. At the end of each test the steel strands were cleaned and re-weighed to determine the mass loss and evaluate it vis-á-vis the AE data. The initiation and propagation phases of corrosion were correlated with the percentage mass loss of steel and the acquired AE signals. Results indicate that AE monitoring may be a useful aid in the detection and differentiation of the steel deterioration phases, and estimation of the locations of corroded areas.

Monitoring corrosion in prestressed concrete beams using acoustic emission technique

Early detection of corrosion can help reduce the cost of maintenance and extend the service life of structures. Acoustic emission (AE) sensing has proven to be a promising method for early detection of corrosion in reinforced concrete members. A test program is presented composed of four medium-scale prestressed concrete T-beams. Three of the beams have a length of 16 ft. 4 in. (4.98 m), and one is 9 ft. 8 in. (2.95 m). In order to corrode the specimens a 3% NaCl solution was prepared, which is representative of sea salt concentration. The beams were subjected to wet-dry cycles to accelerate the corrosion process. Two of the specimens were pre-cracked prior to conditioning in order to examine the effect of crack presence. AE data was recorded continuously while half-cell potential measurements and corrosion rate by Linear Polarization Resistance (LPR) were measured daily. Corrosion current was also being acquired constantly to monitor any change in the concrete resistivity. Results indicate that the onset of corrosion may be identified using AE features, and were corroborated with measurements obtained from electrochemical techniques. Corroded areas were located using source triangulation. The results indicate that cracked specimens showed corrosion activity prior to un-cracked specimens and experienced higher corrosion rates. The level of corrosion was determined using corrosion rate results. Intensity analysis was used to link the corrosion rate and level to AE data.

Characterization of corrosion damage in prestressed concrete using acoustic emission

The corrosion of reinforced concrete structures is a major issue from both a structural safety and maintenance management point of view. Early detection of the internal degradation process provides the owner with sufficient options to develop a plan of action. An accelerated corrosion test was conducted in a small scale concrete specimen reinforced with a 0.5 inch (13 mm) diameter prestressing strand to investigate the correlation between corrosion rate and acoustic emission (AE). Corrosion was accelerated in the laboratory by supplying anodic current via a rectifier while continuously monitoring acoustic emission activity. Results were correlated with traditional electrochemical techniques such as half-cell potential and linear polarization. The location of the active corrosion activity was found through a location algorithm based on time of flight of the stress waves. Intensity analysis was used to plot the relative significance of the damage states present in the specimen and a preliminary grading chart is presented. Results indicate that AE may be a useful non-intrusive technique for the detection and quantification of corrosion damage.

Damage detection in prestressed pile to bent cap connections

South Carolina is one of the most seismically active states in the eastern U.S. Due to this high level of seismic activity, structural health monitoring is important to ensure a high level of confidence in the states infrastructure. The University of South Carolina (U.SC) is currently studying the behavior of prestressed pile to bent-cap connections that are typical of construction used in the state. Bent caps are generally constructed with multiple piles. In these tests single pile specimens were created for both interior and exterior piles. Interior specimens were subjected to a constant compressive load while exterior specimens experienced both compressive and tensile loads. Acoustic Emission (AE) sensing was utilized on fullscale test specimens to investigate the feasibility of detecting and characterizing damage in these connections during a seismic event. Seven full-scale prestressed concrete piles have been embedded into cast-in-place (CIP) reinforced concrete bent caps and tested under reverse cyclic loading. AE data has been gathered with eight strategically placed AE sensors. Preliminary analysis of the data indicates that AE is promising method with respect to the detection of damage prior to detection by visual observation. AE activity is used to detect both the onset and location of cracking and to characterize the extent of damage at later stages of degradation. One focus of the work is to minimize the amount of AE data recorded for the development of wireless systems having low power consumption.