Feasibility of defect detection in concrete cylinders by means of Muon Scattering Radiography (MSR)

Construction Pathology, Rehabilitation Technology and Heritage Management September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 1 CODE 125 FEASIBILITY OF DEFECT DETECTION IN CONCRETE CYLINDERS BY MEANS OF MUON SCATTERING RADIOGRAPHY (MSR) Orio, Aitor1; Martínez, Pablo2; Díez, Carlos1; Gómez, Pablo1 1:Muon Tomography Systems S.L, e-mail: [email protected], web: https://www.linkedin.com/in/aitororioalonso/ e-mail: [email protected], web: https://www.linkedin.com/in/carlosdiezgonzalez/ e-mail: [email protected], web: https://www.linkedin.com/in/pablo-gómez-garcía-b695b4113/ 2: Universidad de Cantabria -CSIC, Isntituto de Física de Cantabria (IFCA) e-mail: [email protected], web: www.cern.ch/pablom ABSTRACT Cosmic muons are elementary particles created in the atmosphere due to the incidence of cosmic rays. These particles reach the surface of the Earth with an approximately constant flux. Muons traverse all objects, and they can be used to create density maps of their interior especially in the case of dense and large objects. To perform a Muon Scattering Radiography (MSR), it is necessary to measure the trajectory of muons before and after crossing the target. The denser the target is, the larger the muon trajectory deviation. The main objective of this research is to establish MSR as a Non-Destructive Testing technique to test the deterioration and defects of concrete structures, where other inspection techniques are difficult or impossible to apply. MSR can detect density changes, cracks and voids in very large objects thanks to its large penetration power. In addition, this technique is fully nondestructive and can be used in applications where delicate structures are involved, such as monuments or ancient buildings, since it does not require any contact with the target. This work focuses on the study of feasibility of the detection of subtle defects in small concrete structures using MSR. Specifically, it is proposed to use muon detectors based on multiwire proportional chambers to collect the data samples. This study used unreinforced concrete cylindrical-shaped samples of 15 cm of diameter and 30 cm of height. Scenarios with different cracks are measured to show the power of the technique. A specific reconstruction algorithm which optimizes the detection capabilities is proposed. Results show that the detection and imaging of full transverse cracks of about 1 cm of aperture is possible with this technique. KEYWORDS: Non-Destructive Testing; Concrete inspection; Muon Scattering Radiography; Cosmic rays; Multiwire Proportional Chambers. 1. INTRODUCTION From the beginnings of Muon Radiography (MR) in the early 1950s, both absorption and scattering of muons has been used to inspect structures inside archaeological constructions and in more modern buildings of civilian use, completing successful experiments that have shown important information about them. In these measurement and analysis campaigns, shafts, voids and cavities have been found and also important information about the stability of constructions and the state of structural elements has been extracted. MR can be applied measuring the absorption or the scattering of muons. The Muon Absorption Radiography (MAR) is adequate for measurement campaigns involving big targets due to REHABEND 2022. September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 2 its capability of scanning big areas in relation to the detector dimensions. This method only needs one detector to measure the incoming muons that have crossed the target. The density map of the scanned area is created counting the number of muons, knowing that they are absorbed when crossing big amounts of dense material. On the other hand, Muon Scattering Radiography (MSR), is appropriate to detect medium and small size targets. In this case, two detectors are needed to measure muon trajectories before and after the target, scanning smaller areas but obtaining the deviation of muons, information which allows to perform more precise reconstructions. These deviations are produced by the Multiple Scattering which suffer charged particles when traversing matter [1]. The larger the muon trajectory deviation is, the denser the measured object. The first application of MR was carried out in 1955 and it involved the MAR inspection of the overburden of a tunnel with a movable detector [2]. This same application has been repeated recently in a UK railway [3]. In the latter campaign, a hidden shaft in the tunnel overburden has been discovered. In relation to the application of MSR in world heritage buildings, studies and laboratory experiments have been done to confirm the feasibility of measuring and assessing the state of reinforcement elements in the dome of Florence Cathedral Santa Maria del Fiore [4] [5]. In the field of archaeology, MAR was applied for the first time in the 1960s, at the Chephren’s Pyramid in Giza (Egypt). The objective was to investigate the existence of hidden chambers, and it was concluded that chambers of these dimensions do not exist in Chephren’s Pyramid [6]. The campaign of measurements performed in the Pyramid of the Sun built by the Aztecs at Teotihuacan (Mexico) had the same objective. A lower density area in the southern side was reported, concluding that its probable cause was a structural weakness [7] [8]. In a Mayan site in Belize, called La Milpa, MAR has also been applied to search hidden chambers [8] [9]. Recently, a big void has been discovered in the Great Pyramid of Giza. The discovery has been confirmed by three different muography teams inside the ScanPyramids project and using different detection technologies [10]. The discovery of a cavity in the Mount Echia, in Naples (Italy), is another example of the potential of MAR to obtain information about these sorts of archaeological constructions [11] [12] [13]. To sum up, MR is a valid technique to explore the state of buildings and structures in a non-destructive way and it can work better compared to other techniques in certain environments and applications. In this paper, a feasibility study about the detection of cracks in cylindrical-shaped concrete made samples is presented. Samples of a diameter of 15 cm with full transverse cracks of 2 cm and 1 cm of aperture, and without crack, have been measured by means of MSR. To perform these experiments, the detection hardware of the company Muon Systems has been used. Muon Systems is an enterprise specialized in Industrial Muon Scattering Radiography which also has published studies of the application of this technique in the fields of manufacturing industry [14] and hydrology [15]. 2. DEVELOPMENT In the following subsections, the detectors, the concrete samples and the scenarios used in the experiments are described. The reconstruction algorithm that has been applied to obtain density maps of the concrete samples is also explained. 2.1. Experimental setup The detectors used in this research were composed of four Multi Wire Proportional Chambers and each one has two perpendicular layers with 224 wires, all of them separated by 4 mm. In the lower part of the detector, there are three chambers, but one of them is not activated. This hardware can be seen in Figure 1 and detects four points of muon trajectories, two points before and another two points after the target. With these points, way-in and way-out trajectories can be reconstructed, and muon deviations can be REHABEND 2022. September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 3 calculated. The synchronization electronics identify a muon when signals are obtained at the same time (technically, in a small space of time) in all the chambers. This condition distinguishes signals produced by muons from signals produced by other charged particles which could activate the detection wires. Figure 1: The detectors of Muon Systems located inside a grey structure with the concrete samples placed between them. Two concrete samples (A and B) have been used to perform the experiments. Both are cylindricalshaped, with a diameter of 15 cm and a height of 30 cm. Their mass, volume and density are specified in the Table 1. Table 1: Mass, volume and bulk density of the two samples used in the experiments. Sample Mass (Kg) Volume (cm3) Density (g/cm3) A 11.35 5300 2.14 B 12.90 5300 2.43 The detection scenarios have been created with these two concrete samples. The first one, which is represented in the left photograph of Figure 2, consists of a unique concrete cylinder (sample A) that represents an intact concrete structure. On the other hand, the second scenario, illustrated in the right photograph of Figure 2, as well as in Figure 1, recreates a cracked concrete structure with the two concrete cylinders. This scenario has been used to measure cracks of an aperture of 2 cm and 1 cm. The purpose of the study presented in this document is to analyse the 20 central centimetres along the longitudinal axis of the cylinders and to find out if the cracks are detected. Since the length of the samples is 30 cm, the analysed area will cover a smaller area comparing to the dimensions of a unique sample. Construction Pathology, Rehabilitation Technology and Heritage Management September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 4 Figure 2: In the left, the scenario that recreates an intact concrete structure. In the right, the scenario used to recreate cracked concrete structures. 2.2. Proposed reconstruction algorithm The reconstruction algorithm used to obtain the results shared in this paper was tested in previous studies with simulations of these scenarios. The simulations were based on the Geant4 software, a standard in Particle Physics [16]. One of the most used algorithms in Muon Radiography is POCA (Point of Closest Approach) and its output is a unique interaction point for each muon [17]. In these previous studies, the POCA algorithm was also evaluated, and limitations in relation to an accurate reconstruction of muon events with small deviations were noticed. These limitations cause the loss of useful information for the detection of small defects in medium density and medium size objects like the concrete samples used in this experiment. Being aware of this, an alternative reconstruction algorithm has been developed. The new algorithm is based on the analysis of the deviations of all muons crossing the target. Since the relative position of the concrete samples in relation to the muon detectors is known, it is possible to identify which muons cross the space where the sample is located. In Figure 3, the points where muons probably enter and go out of this space are shown, coloured in red and green respectively. These calculations have been done according to the detected trajectories and the data plotted in the figure has been extracted from one of the measurements carried out with concrete samples. In this application the purpose is to detect vertical cracks, hence a particular way to divide the sample space has been used, allocating muons in vertical sections of a width of 1 cm depending on the zone where they cross the estimated location of the concrete made sample. Figure 3: Entrance (red) and exit (green) points of the measured muons in relation to the sample location. REHABEND 2022. September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 5 In the reconstruction of the measurements, smaller muon deviations are expected in the areas where a crack is located. According to the Multiple Scattering suffered by muons, their deviations projected on a plane result in a 0 mean gaussian distribution, and the width of the distribution provide a measure of the amount of scattering suffered by them. The performed measurements have been analysed reconstructing images with statistic magnitudes of the width of muon deviation distributions that cross each vertical section. Specifically, the median of the absolute value of deviations has been calculated. This statistic measure behaves in a robust way in measurements with noisy events that present big deviations. The aforementioned events can be caused by electronic noise, as well as by low momentum muons and fake muons [18]. 3. RESULTS By means of the scenarios mentioned in subsection 2.1, three measurements have been made: a first measurement of a concrete structure without crack, and a second and a third one, with full transverse cracks of 1 cm and 2 cm of aperture, respectively. Both cracks were approximately centred in the detection space. The reconstructions obtained using the algorithm described in subsection 2.2 are presented in Figure 4. The origin of coordinates is referenced in the centre of the scanned space, determined by the position of the detectors. Both cracks have been detected, imaging them slightly off centred, almost 1 cm to the positive side of the longitudinal axis. These deviations on sample positions have been confirmed in the laboratory with precise measurements. It must be noticed that the vertical sections where the cracks are located have statistically smaller muon deviations compared to all others. In the case of the 2 cm crack, these differences are clearer. The data taking time for each measurement was 15 hours. Figure 4: Reconstructions of the concrete structure without crack (left), with 1 cm crack (centre) and with 2 cm crack (right). The scanned space is signalled in blue. To confirm these results, a fourth measurement has been done. In this case, a 2 cm crack has been set up, but moving its location 3 cm to the negative side of the longitudinal axis compared with the previous cracks. In the reconstruction of this fourth measurement, the crack has been clearly imaged once again, but its aperture seems to be of 1 cm. Also, the highest deviations are obtained in the negative side of the X axis, where the concrete sample B is located, the heavier one (Figure 5). The highest deviations in the REHABEND 2022. September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 6 reconstructions of the previous measurements of 1 cm and 2 cm cracks highlight the location of sample B, as well (Figure 4). Figure 5: Concrete structure with 2 cm crack, moved 3 cm to the negative side of the longitudinal axis. 4. DISCUSSION The cracks and their locations have been detected in all the measurements. However, the estimation of the aperture of the crack of the fourth measurement has not been correct. The reconstruction shows it as a 1 cm crack. This effect can be produced if a vertical section of 1 cm width is centred within a crack of 2 cm of aperture. In this situation, three vertical sections will be affected by it, but the central section will reflect the lowest deviations. Also, statistical fluctuation and background noise can influence the results. Regarding the efficiency of the measurements, the presence of background noise has been identified. This situation has required the filtering of the detected events, losing part of the muon flux passing through the detectors. However, the results are promising and if the efficiency is improved, the necessary data taking time will be directly reduced. To avoid these issues, future work (explained in section 5) is going to be developed to increase efficiency, precision and reconstruction resolution. 5. CONCLUSIONS The absence of concrete cylindrical sections of 1 cm and 2 cm width have been detected by means of Scattering Muon Radiography. In other words, even the absence of approximately 0.4 Kg of concrete is reflected in muon deviations and the detectors built by the company Muon Systems can measure it. The reconstruction algorithm applied has located the cracks and has estimated their aperture. In addition, the higher density of one of the samples has been clearly imaged in the measurements. The density of the lighter sample is 2.14 g/cm3 (sample A), while the density of the heavier sample is 2.43 g/cm3. It must be mentioned that the proposed algorithm adequately exploits the information contained in all muon events, even in the less deviated, which are difficult to reconstruct properly with POCA algorithm. Future work involves improvements in the detection system to obtain a better resolution that, in this case, will allow the measurement of smaller cracks in the same data taking time. Efficiency, event reconstruction and detection are going to be improved with the use of new hardware configurations and innovative algorithms. A hardware with six detection chambers, which means to have a redundant point for the reconstruction of each muon trajectory, and Smart Tracking algorithms are going to be used to REHABEND 2022. September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 7 remove noise from measurements and reconstruct the muon events in a better and more efficient way. Also, to improve the reconstruction of the target, maximum likelihood estimation and machine learning algorithms are going to be applied. Muon Scattering Radiography is a promising Non-Destructive Testing technique applicable in concrete structures and capable of finding small defects in centimetre scale. These detection capabilities along with its penetration power make the technique useful in civil constructions and buildings. Future progress in the detection hardware and reconstruction algorithms can significantly improve the performance of the technique. 6. ACKNOWLEDGMENTS The support of the Spanish Ministry of Science and Innovation is highly appreciated. This ministry has funded the work of the first author through the program of Industrial Doctorates (Reference: DIN2018009886). The funding and support of the project of Muon Systems by Centro para el Desarrollo Tecnológico Industrial (CDTI) and the Government of the Basque Country is also regarded, as well as the availability of the concrete samples provided by Grupo de Tecnología de la Edificación de la Universidad de Cantabria (GTED-UC). 7. BIBLIOGRAPHY [1] Particle Data Group. 34. Passage of Particles Through Matter. https://pdg.lbl.gov/2021/web/viewer.html?file=%2F2021/reviews/rpp2020-rev-passage-particlesmatter.pdf (accessed: September 2021). [2] George E.P. Cosmic rays measure overburden of tunnel. Commonwealth Engineer; 1955: pp. 455457. [3] Thompson LF, Stowell JP, Fargher SJ, Steer CA, Loughney KL, O’sullivan EM, Gluyas JG, Blaney SW, Pidcock RJ. Muon tomography for railway tunnel imaging. Physical Review Research. 2020;2:23017. https://doi.org/10.1103/PhysRevResearch.2.023017 [4] Guardincerri E, Durham JM, Morris C, Bacon JD, Daughton TM, Fellows S, Morley DJ, Johnson OR, Plaud-Ramos K, Poulson DC, Wang Z. Imaging the inside of thick structures using cosmic rays. AIP Advances. 2016;6(1). https://doi.org/10.1063/1.4940897 [5] Guardincerri E, Bacon JD, Barros N, Blasi C, Bonechi L, Chen A, D’Alessandro R, Durham JM, Fine M, Mauger C, Mayers G, Morris C, Newcomer FM, Okasinski J, Pizzico T, Plaud-Ramos K, Poulson DC, Reilly MB, Roberts A, Saeid T, Vaccaro V, van Berg R. Imaging the dome of Santa Maria del Fiore using cosmic rays. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 2019;377:20180136. https://doi.org/10.1098/rsta.2018.0136 [6] Alvarez LW, Anderson JA, el Bedwei F, Burkhard J, Fakhry A, Girgis A, Goneid A, Hassan F, Iverson D, Lynch G, Miligy Z, Moussa AH, Mohammed-Sharkawi, Yazolino L. Search for hidden chambers in the pyramids. Science. 1970;167(3919):832-839. https://doi.org/10.1126/science.167.3919.832 [7] Aguilar S, Alfaro R, Belmont E, Cadena R, Grabski V, Ibarra T, Lemus V, Manzanilla L, MartinezDavalos A, Menchaca-Rocha A, Moreno M, Sandoval A. Searching for cavities in the Teotihuacan REHABEND 2022. September 13-16, 2022. Granada, Spain REHABEND 2022 Congress 8 Pyramid of the Sun using cosmic muons: preliminary results. Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011. 2011;4:325-328. [8] Melesio L. The pyramid detectives. Physics World. 2014;27 (12):24-27. [9] Maya Muon Research Group. Maya Muon. http://www.hep.utexas.edu/mayamuon/ (accessed: September 2021) [10] Morishima K, Kuno M, Nishio A, Kitagawa N, Manabe Y, Moto M, Takasaki F, Fujii H, Satoh K, Kodama H, Hayashi K, Odaka S, Procureur S, Atti D, Bouteille S, Calvet D, Filosa C, Magnier P, Mandjavidze I, Riallot M, Marini B, Gable P, Date Y, Sugiura M, Elshayeb Y, Elnady T, Ezzy M, Guerriero E, Steige V, Serikoff N, Mouret JB, Charlès B, Helal H, Tayoubi M. Discovery of a big void in Khufu’s Pyramid by observation of cosmic-ray muons. Nature. 2017;552(7685):386-390. https://doi.org/10.1038/nature24647 [11] Saracino G, Amato L, Ambrosino F, Antonucci G, Bonechi L, Cimmino L, Consiglio L, Alessandro RD’, de Luzio E, Minin G, Noli P, Scognamiglio L, Strolin P, Varriale A. Imaging of underground cavities with cosmic-ray muons from observations at Mt. Echia (Naples). Scientific Reports. 2017;7, 1181. https://doi.org/10.1038/s41598-017-01277-3 [12] Saracino G, Ambrosino F, Bonechi L, Cimmino L, Noli P, Scognamiglio L, Strolin P. Applications of muon absorption radiography to the fields of archaeology and civil engineering. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 2019;377: 20180057. https://doi.org/10.1098/rsta.2018.0057 [13] Cimmino L, Baccani G, Noli P, Amato L, Ambrosino F, Bonechi L, Bongi M, Ciulli V, D’Alessandro R, D’Errico M, Gonzi S, Melon B, Minin G, Saracino G, Scognamiglio L, Strolin P, Viliani L. 3D Muography for the Search of Hidden Cavities. Scientific Reports. 2019;9(1). https://doi.org/10.1038/S41598-019-39682-5 [14] Martinez P, Gomez P, Diez C, Orio A. Non-destructive testing of industrial equipment using muon radiography. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 2019;377: 20180054. https://doi.org/10.1098/rsta.2018.0054 [15] Orio A, Alonso E, Gómez P, Díez C, Martínez P. Snow water equivalent measurement using Muon Radiography. https://indico.cern.ch/event/820476/contributions/4372906/ (accessed: October 2021) [16] Geant4, a simulation toolkit. https://geant4.web.cern.ch/ (accessed: October 2021) [17] Sehgal R, Sehgal ST, Dhruv M, Pant LM, Mitra Sengupta M, Roy T. PoCA point cloud filteration algorithm for muon tomography. Proceedings of the DAE international symposium on nuclear physics. 2018:V.63 [18] Bonechi L, D’Alessandro R, Giammanco A. Atmospheric muons as an imaging tool. Reviews in Physics. 2020:vol.5. https://doi.org/10.1016/j.revip.2020.100038