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Reliability of Non-Destructive Testing Methods for Detecting Steel Rebar in Existing Concrete Structures

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Reliability of Non-Destructive Testing Methods for Detecting Steel Rebar in Existing Concrete Structures Eindhoven University of Technology MASTER Reliability of non-destructive testing methods for detecting steel rebar in existing concrete structures Selek, I. Award date: 2015 Link to publication Disclaimer This document contains a student thesis (bachelor's or master's), as authored by a student at Eindhoven University of Technology. Student theses are made available in the TU/e repository upon obtaining the required degree. The grade received is not published on the document as presented in the repository. The required complexity or quality of research of student theses may vary by program, and the required minimum study period may vary in duration. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain EINDHOVEN UNIVERSITY OF TECHNOLOGY Reliability of non-destructive testing methods for detecting steel rebar in existing concrete structures Final Thesis A-2015.113 I.SELEK Author: Name Ibrahim Selek Student number 0717873 Academic year 2014 – 2015 Education Architecture, building and planning Faculty Structural Design Mail address [email protected] Publication: Version Final colloquium Date 15-10-2015 Place Eindhoven Supervisors: 1st supervisor prof.ir. S.N.M. (Simon) Wijte 2nd supervisor prof.dr.ir. T.A.M. (Theo) Salet 3th supervisor ir. M. (Maarten) Swinkels 2 Acknowledgment Handing in my master thesis is the final step in completing the Master of Science program to become a Structural Engineer at Eindhoven University of Technology. Foremost, I would like to express my sincere gratitude to my graduation committee, namely: prof.ir. Simon Wijte, prof.dr.ir. Theo Salet and ir. Maarten Swinkels, for their helpful guidance. Writing this master thesis was a rewarding and interesting process, which would not be possible without the help and support of my graduation committee. Secondly, I would like to thank the five consultants, namely: Theodoor Gijsbers, Mürsel Şahin, Bas Bruins Slot, Ronald van Boekel and Hamid Soori, for measuring and analyzing the specimens. This research would not be possible without reinforced concrete specimens. Therefore, I would like to thank Dikkerboom Betonbroing B.V. and Hurks Prefabbeton B.V. for providing reinforced concrete specimens. I also want to thank Julia Zanona and Niels Arendsen from Hilti for their time and sharing their experiences and knowledge with me. Finally, I would like to thank SGS Intron for the continuous support, interest and immense knowledge during my graduate internship period. I would also like to thank my friends and family for their support during this challenging and stressful period. 3 Abstract In the year 2011, the Netherlands was shocked by a disaster in the city Leeuwarden. One of the cantilevered reinforced concrete gallery plates of the Antillenflat collapsed due to the higher external loading than calculated, less accurate construction and corrosion of the rebar`s. After the Antillenflat disaster, many other apartments, mainly built in the period 1950 – 1970, with cantilevered reinforced concrete gallery plates are considered as hazardous in the Netherlands. These hazardous gallery plates are mainly inspected for the cover depth and rebar diameter with the use of non-destructive testing methods. The graduation project provides information about the reliability of non-destructive testing methods by determining the amount of rebar`s, cover depth and rebar diameter in existing concrete structures. Analyzing the results of the rebar diameter measurements was not unambiguous as was the case with the analysis of the cover depth measurement. There is no guideline given by the manufacturer in order to analyze the rebar diameter measurement results. Therefore, the Block Analysis Method is introduced in the project in order to analyze the rebar diameter measurement results. Several test cases are measured with the use of the covermeter (Hilti Ferroscan PS200) and the Ground Penetrating Radar (Hilti PS1000). The measured amount of rebar`s were fully in line with the real amount of existing rebar`s. Accuracy of the cover depth measurements were also in line with the given range for accuracy, which is provided by the manufacturer. Furthermore, the accuracy of the cover depth measurements significantly increases when the rebar diameter of the measured structure is known. Giving an advice for the rebar diameter measurement with the use of the Block Analysis Method results in an accuracy of ±0.36mm, but the standard deviation is 3.06mm. The standard deviations of the rebar diameter measurement results are significantly large, which means that the spread of the measurement results are spread over a large area. This large spread gives the impression of unreliable measurement results. Furthermore, the accuracy of the measurement results decreases when the rebar diameters is larger than or equal to 20mm. Partly destructive testing the measured structure provides substantial local insight into the rebar diameters and cover depth. Combining non-destructive testing with partly destructive testing results in more reliable knowledge about the analyzed structure and increases the reliability of non-destructive rebar diameter measurement results. 4 The large spread of the measurement results is probably caused by the unexpected effect of concrete on the measurement results. The covermeter creates an electromagnetic field in the reinforced concrete element, measures the disruption of the created electromagnetic field and translates this information to measured cover depth and rebar diameter. Presence of magnetic elements in the concrete element disturbs the created electromagnetic field. Manufacturers of covermeters assumed that only the presence of steel elements effect the disruption of the created electromagnetic field. The influence of the electrical resistivity of concrete on the conduction of the electromagnetic field and the influence of the magnetic permeability of concrete on the disruption of the electromagnetic field are neglected. However, this study gives the impression that the neglected electrical resistivity and magnetic permeability of concrete causes the large spread of the rebar diameter measurement results. 5 Contents 1. Introduction ...................................................................................................................... 8 2. Reinforced concrete ........................................................................................................ 11 2.1 Importance of reinforced concrete ............................................................................ 11 2.2 Structural calculation reinforced concrete................................................................. 12 3. Non-destructive testing methods ................................................................................... 15 3.1 Covermeter Testing Method...................................................................................... 16 3.2 Ground Penetrating Testing Method ......................................................................... 19 3.3 Radiographic Testing Method ................................................................................... 21 4. Devices ............................................................................................................................. 23 4.1 Covermeter Hilti Ferroscan PS200 and GPR Hilti PS1000 ...................................... 23 4.2 Measurement preconditions ...................................................................................... 24 4.2.1 Quickscan measurement .................................................................................... 25 4.2.2 Imagescan measurement .................................................................................... 28 4.3 Declared accuracy Hilti Ferroscan PS200 ................................................................. 30 5. Analyzing methods ......................................................................................................... 32 5.1 Quick Analysis Method for rebar diameter measurement ........................................ 32 5.2 Block Analysis Method for rebar diameter measurement ......................................... 33 5.3 Line Analysis Method for rebar diameter measurement ........................................... 34 6. Test cases ......................................................................................................................... 36 6.1 London City Island .................................................................................................... 37 6.1.1 Specimen I ......................................................................................................... 38 6.1.2 Specimen II ........................................................................................................ 39 6.1.3 Specimen III ....................................................................................................... 40 6.2 Apartment Eikenstraat Leeuwarden .......................................................................... 41 6.2.1 Specimen IV......................................................................................................
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