Showing papers by "Maurice B. Dusseault published in 2020"

Magnetic detection of corroded steel rebar: Reality and simulations

Abstract: Reinforced concrete (RC) is common throughout modern industrial and civil infrastructure. Adding steel reinforcing bars (“rebar”) to concrete improves tensile strength, but if exposed to adverse environmental conditions, rebar may corrode and lead to a progressively deteriorating concrete condition. Several techniques exist for assessing rebar corrosion conditions. Inspection of RC structures based on the self-magnetic concept is a Non-Destructive Testing (NDT) method that helps to quantify the steel reinforcement condition. Corrosion quantification helps to manage the human and financial risks associated with RC structural failure, premature replacement, or inadequate repair. In this study, an intact rebar and one with general corrosion are scanned with a 3D laser scanner. The captured point clouds are imported as real geometries to finite-element software, where their self-magnetic behaviors are simulated under the effect of Earth's magnetic field. Significant differences are found between the self-magnetic behavior of the corroded and intact rebars. For instance, the Y component magnetic flux density values of the intact rebar have a sinuous trend with a period of about 10 mm, equal to the distance between the rebar corrugation peaks, but no harmonic trend can be detected in the rebar with general corrosion. Self-magnetic data of the corroded and intact rebars are recorded and assessed through experiments, and the test results correlate well with the simulation outcomes.

Bridge deck assessment using infrastructure corrosion assessment magnetic method (iCAMM™) technology, a case study of a culvert in Markham city, Ontario, Canada

Abstract: Steel reinforcement corrosion can result in disastrous bridge failures over time. To manage the human and financial risks associated with such unexpected functional bridge failures, the reinforcements' condition should be quantified using Non-Destructive Testing (NDT) methods. In this case history, the condition of culvert C072's reinforced concrete (RC) bridge structure (located in the north of Markham, Ontario, Canada) is inspected. The inspection, carried out under the supervision of the Corporation of the City of Markham, used a passive magnetic-based NDT technology, the Infrastructure Corrosion Assessment Magnetic Method (iCAMM™). The inspection outcomes demonstrate that the sections close to the south and north ends of the bridge display the most-severe reinforcement anomalies: roughly, a maximum of 20% and 14% of the reinforcement's cross-sectional area loss are detected close to the bridging structure's south and north ends. Additionally, an area in the middle of the bridge is found to have a noticeable anomaly in the reinforcement. The results generated from the magnetic data, collected using an iCAMM™ scanner, are in good agreement with visual-investigation results and the culvert's historical information, such as the concrete's chloride content and compressive strength values, as well as information from a half-cell potential survey. Culvert C072's condition is considered moderately deteriorated and corrective actions are recommended.

Magnetic Data Pattern Features at Longitudinal Defect Sites in Rebars Scanned by a Passive Magnetic Inspection Technology

Abstract: Reinforced concrete is a versatile modern construction material. Despite its advantages as a composite material, corrosion of the embedded reinforcing steel leads to infrastructure deterio...

Effects of a Fracture on Ultrasonic Wave Velocity and Attenuation in a Homogeneous Medium

Abstract: Nondestructive ultrasonic testing is commonly used to assess damage in infrastructure mostly based on elastic wave velocity. This study focuses on understanding the effects of a thin fracture not only on ultrasonic elastic wave velocity but also on attenuation. Experiments are performed to quantitatively assess the effects of a thin fracture within polymethylmethacrylate (PMMA) specimens. Wave velocity and attenuation are measured across the width of these homogeneous specimens using the ultrasonic pulse velocity method. Seventeen specimens are tested for three different conditions (intact, with a hole, and with a fracture) for two different thicknesses. First, specimens made of two PMMA blocks with an intact fused interface are tested; then, specimens with a small hole (created for generating stress concentration) perpendicular to the interface and milled ends are tested; and, finally, specimens with an induced fracture at the fused interface are tested. Four additional specimens, two with fused (but weak) interfaces between blocks and two solid blocks, are tested during fracture growth under uniaxial strain-controlled test conditions. In fact, wave attenuation can cause the first arrival to be undetected and overestimated by up to 10 %. This error in the selection of the first arrival could be misinterpreted as a change in wave velocity when fractures are present in the material. Although wave velocity shows marginal reduction, less than 4 %, when a thin fracture is present, wave energy attenuates by up to 60 %. This work demonstrates quantitatively that wave attenuation measurements from selected frequency bands in the Fourier spectra can be used to identify the presence of thin fractures using ultrasonic testing.