Applied Radiation and Isotopes 94 (2014) 8–13
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
Prompt gamma ray evaluation for chlorine analysis in blended cement concrete A.A. Naqvi a,n, M. Maslehuddin b, Zameer Kalakada c, O.S.B. Al-Amoudi c a
Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia Center for Engineering Research, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia c Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia b
H I G H L I G H T S
New data on chlorine measurements in BFS cement concrete is presented. Single chlorine gamma ray was evaluated for chlorine analysis in blended cement concrete. 6.11 MeV gamma-rays were found to be optimum one for chlorine analysis in the blended concretes.
art ic l e i nf o
a b s t r a c t
Article history: Received 16 January 2014 Received in revised form 9 June 2014 Accepted 13 June 2014 Available online 8 July 2014
Single prompt gamma ray energy has been evaluated to measure chlorine concentration in fly ash (FA), Super-Pozz (SPZ) and blast furnace slag (BFS) cement concrete specimens using a portable neutron generator-based Prompt Gamma Neutron Activation (PGNAA) setup. The gamma ray yield data from chloride concentration measurement in FA, SPZ and BFS cement concretes for 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays were analyzed to identify a gamma ray with common slope (gamma ray yield/Cl conc. wt%) for the FA, BFS and SPZ cement concretes. The gamma ray yield data for FA and SPZ cement concretes with varying chloride concentration were measured previously using a portable neutron generator-based PGNAA setup. In the current study, new data have been measured for chlorine detection in the BFS cement concrete using a portable neutron generator-based PGNAA setup for 2.86–3.10, 5.72, and 6.11 MeV chlorine gamma rays. The minimum detection limit of chlorine in BFS cement concrete (MDC) was found to be 0.03470.010, 0.03270.010, 0.03370.010 for 2.86–3.10, 5.72 and 6.11 MeV gamma ray, respectively. The new BFS cement concrete data, along with the previous measurements for FA and SPZ cement concretes, have been utilized to identify a gamma ray with a common slope to analyze the Cl concentration in all of these blended cement concretes. It has been observed that the 6.11 MeV chlorine gamma ray has a common slope of 52957265 gamma rays/wt % Cl concentration for the portable neutron generator-based PGNAA setup. The minimum detectable concentration (MDC) of chlorine in blended cement concrete was measured to be 0.03370.010 wt % for the portable neutron generator-based PGNAA. Thus, the 6.11 MeV chlorine gamma ray can be used for chlorine analysis of blended cement concretes. & 2014 Elsevier Ltd. All rights reserved.
Keywords: Single prompt gamma ray evaluation for chlorine analysis Portable neutron generator Blended cement concrete samples Monte carlo simulation
1. Introduction Corrosion of reinforcing steel is mainly caused by the diffusion of chloride ions to the steel surface. These ions either diffuse from the service environment or are present in the mixture ingredients (Maslehuddin et al., 1996; ACI Committee 222, 1989; Al-Amoudi et al., 2001). One preventive measure against reinforcement corrosion is making the concrete dense and impermeable. Pozzolanic
n
Corresponding author. E-mail address: [email protected] (A.A. Naqvi).
http://dx.doi.org/10.1016/j.apradiso.2014.06.011 0969-8043/& 2014 Elsevier Ltd. All rights reserved.
materials, such as blast furnace slag (BFS), fly ash (FA), silica fume (SF), Super-Pozz (SPZ) and others, are added to concrete as a partial replacement for Portland cement, to make it dense and impermeable, thereby slowing the diffusion of the chloride ions to the steel surface (Al-Amoudi, 2002; PCI Committee, 1994). The Prompt Gamma Neutron Activation (PGNAA) technique is a nondestructive method that can be utilized to determine the chloride concentration in bulk concrete samples (Saleh and Livingston, 2000; Paul and Lindstrom, 2000; Gardner et al., 2000; Naqvi et al., 2012a, 2012b; Chichester and Simpson Lemchak). BFS is in itself cement. However, approximately 20 to 40% cement is added to it to enhance its cementing properties. BFS is
A.A. Naqvi et al. / Applied Radiation and Isotopes 94 (2014) 8–13
known to significantly reduce the risk of damage caused by the alkali–silica reaction, provides good resistance to chloride ingress, reduces the risk of reinforcement corrosion and provides good resistance to attacks by sulfate and other chemicals. Furthermore, the process of manufacturing Portland cement is costly, and it is a major contributor of greenhouse gases, responsible for approximately 5% of all global carbon dioxide emissions. Minimization of the use of Portland cement in concrete without the loss of concrete strength is highly desirable. As shown in Table 1 (Naqvi et al., 2012a, 2012b), BFS cement is characterized by reduced iron oxide, silica and lime contents and enhanced alumina and MgO contents compared to Type I or Type II Portland cement. It contains SiO2 (27.70 wt%), Al2O3 (12.80 wt%), Fe2O3 (1.20 wt%), CaO (44.0 wt%) and MgO (8.80 wt%). While blended cements are utilized to minimize reinforcement corrosion, a non-destructive technique is required for monitoring the chloride concentration in concrete and thus decreasing the chances of reinforcement corrosion. The PGNAA technique is a non-destructive technique that can be used to analyze chloride concentration in bulk cement concrete samples (Saleh and Livingston, 2000; Paul and Lindstrom, 2000; Gardner et al., 2000; Naqvi et al., 2012a, 2012b; Chichester and Simpson Lemchak). In the PGNAA technique, the sensitivity of chlorine detection is affected by the interference between gamma rays from chlorine and calcium (Naqvi et al., 2012a, 2012b). Concrete containing different calcium concentrations is expected to lead to different chlorine detection sensitivities. As shown in Table 1, replacement of Portland cement with FA, SF, SPZ or BFS to increase the corrosion resistance also changes the calcium concentration in concrete. This in turn may affect the chloride detection sensitivity in blended cement concrete, thereby resulting in different values for the minimum detectable concentration (MDC) of chloride. Therefore, it is of interest to compare the MDC of chloride in blended cement concretes utilizing the PGNAA technique. Furthermore, it will be worthwhile to analyze various types of blended cement concretes utilizing a single energy gamma ray with a common slope. This requires a search for a single gamma ray with a common slope (gamma ray yield/Cl conc. wt%) for all cement concrete types to be analyzed using the specific PGNAA setup. In this study, a single energy gamma ray was sought for the analysis of FA, BFS and SPZ cement concrete specimens using a portable neutron generator-based PGNAA setup developed by the authors. Previously, the chloride concentration in FA and SPZ blended cement concretes was measured using a DD portable neutron generator-based PGNAA setup (Naqvi et al., 2012a, 2012b). In the present study, the chloride concentration has been measured in BFS cement concrete utilizing the portable neutron generator-based PGNAA setup (Naqvi et al., 2012a, 2012b). From the measured chloride concentration data from FA, BFS and SPZ cement concrete specimens, a single energy gamma ray with a
9
common slope for all concrete types has been determined. The two parts of the study are described in the following sections.
2. Prompt gamma ray analysis of BFS cement concrete specimens The chlorine concentration in BFS cement concrete specimens containing 0.8–3.5 wt% chloride was measured utilizing a portable neutron generator based-PGNAA setup that has been described in detail elsewhere (Naqvi et al., 2012a, 2012b). For continuity, it will also be described in detail here. The PGNAA setup mainly consists of a portable neutron generator, a cylindrical 25 cm 8 cm (diameter x height) high-density polyethylene (HDPE) moderator, a cylindrical 25 cm 14 cm (diameter x height) chlorine-contaminated BFS cement concrete specimen and a cylindrical 5 cm 5 cm (diameter height) BGO gamma ray detector. The concrete specimen was placed on one side of the neutron generator target-plane location, with the axis of symmetry aligned at a right angle to the neutron generator axis. The HDPE moderator was placed between the specimen and the neutron generator with its axis of symmetry aligned with the axis of the concrete specimen. The BGO detector views the concrete specimen at an angle of 451 with respect to its axis of symmetry, as shown in Fig. 1. To prevent undesired gamma rays and neutrons from reaching the detector, lead, tungsten, and paraffin, neutron shielding is inserted between the neutron generator, the moderator and the BGO detector, as shown in Fig. 1. The paraffin neutron shielding is made of a mixture of paraffin and lithium carbonate mixed in equal weight proportions. The cylindrical BFS cement concrete specimens were prepared by mixing 20 wt% BFS as a replacement of cement. The BFS cement concrete
Fig. 1. Schematic of the MP320 portable neutron generator-based PGNAA setup used to measure the prompt gamma-ray yield.
Table 1 Chemical composition (wt%) of Portland and Blended Cements and coarse and fine aggregates Naqvi et al., 2012a, 2012b. Compound
Type V cement
Type I cement
Fly ash
Blast furnace slag
Silica fume
Superpozz
Fine aggregate
Coarse aggregate
SiO2 Al2O3 Fe2O3 CaO CaCO3 MgO SO3 K2O Na2O
22.00 4.08 4.24 64.07 – 2.21 1.96 0.31 0.21
20.52 5.64 3.80 64.35 – 2.11 2.1 0.36 0.19
52.30 25.20 4.6 10.0 – 2.20 0.60 0.10 0.10
27.70 12.80 1.20 44.0 – 8.80 3.10 0.10 0.40
92.50 0.40 0.40 0.50 – 0.90 0.50 0.40 0.10
53.50 34.3 3.6 4.4 – 1.0 – – –
90.70 1.40 0.48 – 5.62 0.26 0.2 0.43 0.17
4.29 0.20 0.23 – 93.20 0.44 0.4 0.09 0.03
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specimens were prepared with 0.8, 2.0, and 3.5 wt% chlorine contamination following a procedure that has been described elsewhere (Naqvi et al., 2012a). The chlorine-contaminated BFS cement concrete specimens were then irradiated in the newly designed portable neutron generator-based PGNAA setup. A pulsed neutron beam of 2.5 MeV was produced via a D(d,n) reaction utilizing a MP320 portable neutron generator. The neutron generator was operated with a 70 keV deuteron beam with a pulse width of 5 ms and a frequency of 250 Hz. The pulsed neutron beam improves the signal-to-background ratio in PGNAA studies. The typical beam current of the generator was 70 μA. The thermal neutron spectra were acquired in a PC-based data acquisition system utilizing multichannel buffer modules. The prompt gamma ray data from chloride-contaminated BFS cement concrete specimens were acquired for 120 min. For background subtraction, the prompt gamma ray data were also acquired from a BFS cement concrete specimen without chloride contamination. Fig. 2 shows interference of full energy (F) and single escape (S) peaks of prompt gamma rays from the BGO detector material and BFS cement concrete specimens containing 0.8, 2.0, and 3.5 wt% chlorine above 2.66 MeV gamma ray energy. These findings are consistent with previously reported observations (Naqvi et al., 2012a, 2012b). The full energy peaks (F) of the prompt gamma rays are marked in Fig. 2. The large peak on the right end of the spectrum is the gamma ray sum peak from activation of the BGO detector, as was observed in previous measurements (Naqvi et al., 2012a, 2012b). For our large-size BGO detector, the sum peak is observed at 7.33 MeV. Several prompt gamma rays are emitted by chlorine due to the capture of thermal neutrons (Naqvi et al., 2012a, 2012b). The chlorine prompt gamma rays with energies in excess of 2.66 MeV were considered in this study. Due to the poor energy resolution of the BGO detector, chlorine prompt gamma rays with energies of 2.86–3.10, 5.72 and 6.11 MeV from BFS cement concrete could be resolved. Fig. 2 shows well-resolved full energy peaks of the concrete constituents in addition to interference between prompt gamma rays from chlorine and prompt gamma rays from the BFS cement concrete constituents and the BGO detector material, as was observed previously (Naqvi et al., 2012a, 2012b). Fig. 2 shows full energy peaks of the concrete constituents at Si (F) 3.54, Si (F) 4.94 and Ca (F) 4.42 MeV (Naqvi et al., 2012a, 2012b). Additionally, Fig. 2 also shows interference between prompt gamma rays from chlorine with prompt gamma rays from the BFS cement concrete constituents and the BGO detector
material (Naqvi et al., 2012a, 2012b). The 6.62–6.63 MeV Cl (F) peak interferes with the 6.42 MeV Ca(F) peak as well as with the 6.71 and 6.72 MeV Ge(F) peaks. The 6.62–6.63 MeV gamma rays from chlorine interfere with the 6.42 and 6.71–6.72 MeV gamma rays from Ge in the BGO detector material (Naqvi et al., 2012a, 2012b). The Cl(F) 6.11 MeV gamma ray, which interferes with the unlabeled Ca(S) 6.42 MeV gamma ray, is quite prominent in Fig. 2. Similarly, the Cl(F) 5.72 MeV gamma ray interferes with the Cl(S) 6.11 MeV gamma ray. An unresolved broad chlorine prompt gamma ray peak has been observed due to the interference of Cl(F) 2.86 and Cl(F) 3.10 MeV (Naqvi et al., 2012a, 2012b). Finally, the chlorine gamma ray yield from each of the chloridecontaminated BFS cement concrete specimens was obtained after subtraction of the normalized prompt gamma ray spectra of pure BFS cement concrete specimen, described elsewhere in detail (Naqvi et al., 2012a, 2012b). Figs. 3 and 4 show the subtracted spectra of chlorine prompt gamma rays over 2.44–4.49 MeV and 4.58–6.63 MeV, respectively, from BFS cement concrete specimens containing 0.8, 2.0, and 3.5 wt% chlorine. Three prominent chlorine full energy gamma ray peaks corresponding to 2.86–3.10, 5.72 and 6.11 MeV energies are clearly shown in Figs. 3 and 4. The counts under each peak were integrated from the spectra of three BFS cement concrete specimens containing different chlorine concentrations. Fig. 5 shows the normalized experimental yield of 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays as a function of chlorine concentration in the BFS cement concrete. Due to strong interference of the Ge peak from the BGO detector and the calcium peak of concrete with the 6.62–6.63 MeV chlorine gamma
Fig. 3. Enlarged prompt gamma-ray experimental pulse height difference spectrum after background subtraction from the three BFS cement concrete specimens, showing full energy prompt gamma-ray peaks at 2.86–3.10 MeV.
Fig. 2. Enlarged experimental pulse height spectra of prompt gamma-rays of chloride-contaminated BFS cement concrete containing 0.8, 2.0 and 3.5 wt% chlorine taken with the BGO detector (The background spectrum taken with uncontaminated BFS cement concrete is also superimposed for comparison purposes).
Fig. 4. Enlarged prompt gamma-ray experimental pulse height difference spectrum after background subtraction from the three BFS cement concrete specimens, showing full energy prompt gamma-rays peaks at 5.72 and 6.11 MeV.
A.A. Naqvi et al. / Applied Radiation and Isotopes 94 (2014) 8–13
ray peak, this chlorine peak could not be included in the chlorine analysis. Within the experimental uncertainties, the results are in excellent agreement with the normalized calculated yield of the prompt gamma rays from chlorine in BFS cement concrete (shown with a solid line) obtained through Monte Carlo simulations following a previously described procedure (Naqvi et al., 2012a, 2012b) using the code MCNP4B2 (Briesmeister, 1997). For comparison purposes, Figs. 6 and 7 show the normalized experimental yield of 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays as a function of chlorine concentration in the FA cement concrete specimen (Chichester and Simpson Lemchak) and the SPZ cement concrete specimen (Briesmeister, 1997) reported previously. The minimum detectable concentration (MDC) of chlorine in the BFS cement concrete was calculated using the procedure described in Refs. Naqvi et al., 2012a, 2012b. Table 2 shows the MDC of chlorine in the BFS cement concrete specimens determined by the portable neutron generator-based PGNAA setup for the 2.86–3.10, 5.72 and
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6.11 MeV chlorine prompt gamma rays. Also included in Table 2 are the MDCs of chlorine prompt gamma rays in plain, FA (Naqvi et al., 2012b) and SPZ (Naqvi et al., 2012a) cement concretes obtained utilizing the portable neutron generator-based PGNAA setup. The MDCs of chlorine prompt gamma rays in BFS cement concrete specimens for the portable neutron generator-based PGNAA setup were measured as 0.03470.010, 0.03270.010, 0.03370.010 wt% for 2.86–3.10, 5.72 and 6.11 MeV gamma rays, respectively. Within experimental uncertainties, the MDCs of chlorine in the BFS cement concrete measured for 2.86–3.10, 5.72 and 6.11 MeV gamma rays are in accord. The MDC values measured in the present study are also in accord with the MDC value for 6.11 MeV chlorine prompt gamma rays measured in FA and SPZ cement concretes measured using the portable neutron generator-based PGNAA setup (Naqvi et al., 2012a, 2012b). The maximum permissible chloride concentration in Portland cement concrete according to the American Concrete Institute Committee 318 is 0.03 wt% (ACI Committee 222, 1989). Within statistical uncertainty, the lower bound of the MDC of chlorine measured in the present study meets the maximum permissible limit of 0.03 wt% chloride set by ACI Committee 318 (ACI Committee 222, 1989). Based on the data presented in this study, it can be concluded that the portable neutron generator-based PGNAA setup can be used successfully for the non-destructive determination of chlorine in FA, BFS and SPZ cement concretes. An application has been filed with US Patent Office to register the portable neutron generator-based PGNAA setup for the detection of chlorine in plain and blended concrete structures in the field.
Fig. 5. integrated yields of 2.86–3.1, 5.72 and 6.11 MeV prompt gamma-rays as a function of chlorine concentration for the three BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
Fig. 7. Integrated yields of 2.86–3.10, 5.72 and 6.11 MeV prompt gamma-ray peaks as a function of chlorine concentration in the SPZ cement concrete specimens (Briesmeister, 1997). Solid line represents the calculated yield obtained through Monte Carlo simulations.
Table 2 MDC of chlorine in blended cement concrete using the portable neutron generator based PGNAA setup Naqvi et al., 2012a, 2012b. MDC of Chlorine in Blended Cement Concrete(wt%)
Fig. 6. Integrated yields of 2.86–3.1, 5.72 and 6.11 MeV prompt gamma-rays as a function of chlorine concentration in the FA cement concrete specimens (Chichester and Simpson Lemchak). Solid line represents the calculated yield obtained through Monte Carlo simulations.
Gamma-ray energy (MeV)
BFS Cement concrete (Present study)
FA cement concrete SPZ cement Naqvi et al., 2012b concrete Naqvi et al., 2012a
2.86–3.10 5.72 6.11
0.034 70.010 0.032 70.010 0.03370.010
0.0337 0.010 0.0317 0.010 0.032 7 0.010
0.032 7 0.012 0.0377 0.012 0.0357 0.012
12
A.A. Naqvi et al. / Applied Radiation and Isotopes 94 (2014) 8–13
3. Single prompt gamma ray evaluation for chlorine analysis of FA, BFS and SPZ cement concrete specimens The measured gamma ray yield vs chlorine concentration data for FA, BFS and SPZ cement concrete specimens were sorted separately for each of the 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays. Then, each gamma ray yield for the FA, BFS and SPZ cement concretes was plotted against the chlorine concentration (wt%). Figs. 8–10 show the combined yield plot of the FA, BFS and SPZ cement concrete specimens as a function of chlorine concentration for all three gamma rays. The slopes of each of the gamma ray lines for the FA, SPZ and BFS cement concrete specimens are listed in Table 3. Also listed in Table 3 are the correlation coefficients (R2) calculated for the three gamma ray lines. The error in peak counts in the difference spectra was calculated from the square root of the sum of squares of total counts and background counts in the subtracted spectra. The errors in slope and correlation coefficient in the integrated yield vs chlorine concentration were calculated using a standard least square fit. Fig. 8 shows the 2.86–3.10 MeV gamma ray yield vs Cl concentration (wt%) for the FA, SPZ and BFS cement concrete specimens. The slope is 34167500 gamma rays/Cl wt%. There is a large scatter in the data indicated by a relatively poor value of the correlation coefficient (0.83). Fig. 9 shows the 5.72 MeV gamma ray yield vs Cl concentration (wt%) for the FA, SPZ and BFS cement concrete specimens. The slope is 38397192 gamma rays/Cl wt%. There is lesser scatter in the data compared to the 2.86–3.10 MeV gamma
Fig. 8. Integrated yields of 2.86–3.10 prompt gamma-rays as a function of chlorine concentration in FA, SPZ and BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
Fig. 10. Integrated yields of 6.11 MeV prompt gamma-rays as a function of chlorine concentration in FA, SPZ and BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
Table 3 Slope (gamma-ray yield/Cl concentration in wt% ) of gamma rays for combined FA, BFS and SPZ cement concretes specimen. Gamma-ray energy (MeV)
Slope of gamma ray yield ( gamma ray yield /Cl concentration (wt%))
Correlation coefficient R2
2.86–3.10 5.72 6.11
34167 975 3839 7 192 5294 7 171
0.83 0.99 0.99
ray yield data, and the value of the correlation coefficient increased to 0.99. Finally, Fig. 10 shows the 6.11 MeV gamma ray yield vs Cl concentration (wt%) for the FA, SPZ and BFS cement concrete specimens. The slope is 52947171 gamma rays/Cl wt%. There is also less scatter in the data, indicated by the large value of the correlation coefficient (0.99). Out of these three gamma rays, only the 5.72 and 6.11 MeV gamma rays have good correlation and can be used to detect chlorine in blended concrete. Because the 6.11 MeV gamma ray has a larger slope of 52947171 gamma rays/Cl wt% compared to the 5.72 MeV gamma ray, which has a slope of 38397192 gamma rays/Cl wt%., the 6.11 MeV gamma ray is a better choice for detecting chloride in blended concrete. Due to its 38% larger slope than that of the 5.72 MeV gamma ray, the 6.11 MeV gamma ray provides better chlorine detection sensitivity in blended cement concretes.
4. Conclusions
Fig. 9. Integrated yields of 5.72 MeV prompt gamma-rays as a function of chlorine concentration in the FA, SPZ and BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
The optimum energy of a prompt gamma ray that can be utilized to determine the chloride concentration in fly ash, blast furnace slag and Super-Pozz cement concretes utilizing a portable neutron generator-based PGNAA setup has been evaluated. The chlorine concentration in BFS cement concrete was measured using 2.86–3.10, 5.72 and 6.11 MeV chlorine prompt gamma rays. The minimum detected concentrations (MDCs) of chlorine in BFS cement concrete were found to be 0.034 7 0.010, 0.0327 0.010, 0.03370.010 for 2.86–3.10, 5.72 and 6.11 MeV gamma rays, respectively. The slopes of gamma ray yield vs chlorine concentration curves for the three blended cement concrete specimens were compared for each of the three (2.86–3.10, 5.72 and 6.11 MeV) chlorine gamma rays. The gamma ray with the maximum value of common slope (gamma ray yield/Cl conc. wt%) for all the three concrete specimens was identified. It was determined that 6.11 MeV chlorine gamma ray has the best sensitivity for the detection of chlorine
A.A. Naqvi et al. / Applied Radiation and Isotopes 94 (2014) 8–13
in blended cement concrete because the value of the slope of gamma ray yield vs chlorine concentration is 38% more than that of the 5.72 MeV gamma ray. Thus, the 6.11 MeV gamma ray can be used for the chlorine analysis of FA, SPZ and BFS concrete specimens with the portable neutron generator-based PGNAA setup. The results of this study show that the portable neutron generator can be utilized for evaluating the chloride contamination in concrete in the field using 6.11 MeV chlorine prompt gamma rays. Acknowledgments The study is part of project ♯ RG1008 funded by the King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia. The support provided by the Department of Physics, Center for Engineering Research and Department of Civil and Environmental Engineering at KFUPM is also acknowledged. References ACI Committee 222, 1989. (ACI 222R-89). Corrosion of Metals in Concrete. American Concrete Institute, Detroit, USA.
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Al-Amoudi, O.S.B., 2002. Durability of Plain and Blended Cements in Marine Environments (July). Adv. Cement Res. 14 (3), 89–100. Al-Amoudi, O.S.B., Maslehuddin, M., Bader, M.A., 2001. Characteristics of silica fume and its impact on concrete in the Arabian Gulf (February). Concrete 35 (2), 45–50. Briesmeister J.F. (Ed). MCNP4B2 –A General Monte Carlo N-Particles Transport Code. Los Alamos National Laboratory Report, LA-12625. Version 4A. Los Alamos National Laboratory Report, LA-12625-M, 1997. Chichester, D.L., J.D. Simpson and M. Lemchak, Advanced compact accelerator neutron generator technology for active neutron interrogation field work, Journal of Radio Analytical and Nuclear Chemistry, 271, 629–637, 2007. Gardner, R.P., El, Sayyed, Yuanshui, Zheng, Hayden, S., Mayo, C.W., 2000. NaI detectors activation spectra for PGNAA applications. Appl. Radiat. Isot. 53, 483–497. Maslehuddin, M., Page, C.L., Rasheeduzzafar, 1996. J. Mater. Civil Eng. 8, 63. Naqvi, A.A., Kalakada, Zameer, Al-Matouq, Faris A., Maslehuddin, M., Al-Amoudi, O. S.B., 2012a. Prompt gamma ray analysis of chlorine in superpozz cement concrete. Nucl. Inst. Methods Phys. Res., A 693, 67–73. Naqvi, A.A., Kalakada, Zameer, Al-Matouq, Faris A., Maslehuddin, M., Al-Amoudi, O. S.B., 2012b. Chlorine detection in fly ash concrete using a portable neutron generator. Appl. Radiat. Isot. 70, 1671–1674. PCI Committee, 1994. Guide to using silica fume in precast/prestressed concrete products (September–October). PCI J. 39 (5), 36–45. Paul, R.L., Lindstrom, R.M., 2000. Prompt gamma ray activation analysis: fundamentals and applications. J. Radioanal. Nucl. Chem. 243, 181–189. Saleh, H.H., Livingston, R.A., 2000. Experimental evaluation of a portable neutronbased gamma-spectroscopy system for chloride measurements in reinforced concrete. J. Radioanal. Nucl. Chem. 244, 367.
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
Prompt gamma ray evaluation for chlorine analysis in blended cement concrete A.A. Naqvi a,n, M. Maslehuddin b, Zameer Kalakada c, O.S.B. Al-Amoudi c a
Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia Center for Engineering Research, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia c Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia b
H I G H L I G H T S
New data on chlorine measurements in BFS cement concrete is presented. Single chlorine gamma ray was evaluated for chlorine analysis in blended cement concrete. 6.11 MeV gamma-rays were found to be optimum one for chlorine analysis in the blended concretes.
art ic l e i nf o
a b s t r a c t
Article history: Received 16 January 2014 Received in revised form 9 June 2014 Accepted 13 June 2014 Available online 8 July 2014
Single prompt gamma ray energy has been evaluated to measure chlorine concentration in fly ash (FA), Super-Pozz (SPZ) and blast furnace slag (BFS) cement concrete specimens using a portable neutron generator-based Prompt Gamma Neutron Activation (PGNAA) setup. The gamma ray yield data from chloride concentration measurement in FA, SPZ and BFS cement concretes for 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays were analyzed to identify a gamma ray with common slope (gamma ray yield/Cl conc. wt%) for the FA, BFS and SPZ cement concretes. The gamma ray yield data for FA and SPZ cement concretes with varying chloride concentration were measured previously using a portable neutron generator-based PGNAA setup. In the current study, new data have been measured for chlorine detection in the BFS cement concrete using a portable neutron generator-based PGNAA setup for 2.86–3.10, 5.72, and 6.11 MeV chlorine gamma rays. The minimum detection limit of chlorine in BFS cement concrete (MDC) was found to be 0.03470.010, 0.03270.010, 0.03370.010 for 2.86–3.10, 5.72 and 6.11 MeV gamma ray, respectively. The new BFS cement concrete data, along with the previous measurements for FA and SPZ cement concretes, have been utilized to identify a gamma ray with a common slope to analyze the Cl concentration in all of these blended cement concretes. It has been observed that the 6.11 MeV chlorine gamma ray has a common slope of 52957265 gamma rays/wt % Cl concentration for the portable neutron generator-based PGNAA setup. The minimum detectable concentration (MDC) of chlorine in blended cement concrete was measured to be 0.03370.010 wt % for the portable neutron generator-based PGNAA. Thus, the 6.11 MeV chlorine gamma ray can be used for chlorine analysis of blended cement concretes. & 2014 Elsevier Ltd. All rights reserved.
Keywords: Single prompt gamma ray evaluation for chlorine analysis Portable neutron generator Blended cement concrete samples Monte carlo simulation
1. Introduction Corrosion of reinforcing steel is mainly caused by the diffusion of chloride ions to the steel surface. These ions either diffuse from the service environment or are present in the mixture ingredients (Maslehuddin et al., 1996; ACI Committee 222, 1989; Al-Amoudi et al., 2001). One preventive measure against reinforcement corrosion is making the concrete dense and impermeable. Pozzolanic
n
Corresponding author. E-mail address: [email protected] (A.A. Naqvi).
http://dx.doi.org/10.1016/j.apradiso.2014.06.011 0969-8043/& 2014 Elsevier Ltd. All rights reserved.
materials, such as blast furnace slag (BFS), fly ash (FA), silica fume (SF), Super-Pozz (SPZ) and others, are added to concrete as a partial replacement for Portland cement, to make it dense and impermeable, thereby slowing the diffusion of the chloride ions to the steel surface (Al-Amoudi, 2002; PCI Committee, 1994). The Prompt Gamma Neutron Activation (PGNAA) technique is a nondestructive method that can be utilized to determine the chloride concentration in bulk concrete samples (Saleh and Livingston, 2000; Paul and Lindstrom, 2000; Gardner et al., 2000; Naqvi et al., 2012a, 2012b; Chichester and Simpson Lemchak). BFS is in itself cement. However, approximately 20 to 40% cement is added to it to enhance its cementing properties. BFS is
A.A. Naqvi et al. / Applied Radiation and Isotopes 94 (2014) 8–13
known to significantly reduce the risk of damage caused by the alkali–silica reaction, provides good resistance to chloride ingress, reduces the risk of reinforcement corrosion and provides good resistance to attacks by sulfate and other chemicals. Furthermore, the process of manufacturing Portland cement is costly, and it is a major contributor of greenhouse gases, responsible for approximately 5% of all global carbon dioxide emissions. Minimization of the use of Portland cement in concrete without the loss of concrete strength is highly desirable. As shown in Table 1 (Naqvi et al., 2012a, 2012b), BFS cement is characterized by reduced iron oxide, silica and lime contents and enhanced alumina and MgO contents compared to Type I or Type II Portland cement. It contains SiO2 (27.70 wt%), Al2O3 (12.80 wt%), Fe2O3 (1.20 wt%), CaO (44.0 wt%) and MgO (8.80 wt%). While blended cements are utilized to minimize reinforcement corrosion, a non-destructive technique is required for monitoring the chloride concentration in concrete and thus decreasing the chances of reinforcement corrosion. The PGNAA technique is a non-destructive technique that can be used to analyze chloride concentration in bulk cement concrete samples (Saleh and Livingston, 2000; Paul and Lindstrom, 2000; Gardner et al., 2000; Naqvi et al., 2012a, 2012b; Chichester and Simpson Lemchak). In the PGNAA technique, the sensitivity of chlorine detection is affected by the interference between gamma rays from chlorine and calcium (Naqvi et al., 2012a, 2012b). Concrete containing different calcium concentrations is expected to lead to different chlorine detection sensitivities. As shown in Table 1, replacement of Portland cement with FA, SF, SPZ or BFS to increase the corrosion resistance also changes the calcium concentration in concrete. This in turn may affect the chloride detection sensitivity in blended cement concrete, thereby resulting in different values for the minimum detectable concentration (MDC) of chloride. Therefore, it is of interest to compare the MDC of chloride in blended cement concretes utilizing the PGNAA technique. Furthermore, it will be worthwhile to analyze various types of blended cement concretes utilizing a single energy gamma ray with a common slope. This requires a search for a single gamma ray with a common slope (gamma ray yield/Cl conc. wt%) for all cement concrete types to be analyzed using the specific PGNAA setup. In this study, a single energy gamma ray was sought for the analysis of FA, BFS and SPZ cement concrete specimens using a portable neutron generator-based PGNAA setup developed by the authors. Previously, the chloride concentration in FA and SPZ blended cement concretes was measured using a DD portable neutron generator-based PGNAA setup (Naqvi et al., 2012a, 2012b). In the present study, the chloride concentration has been measured in BFS cement concrete utilizing the portable neutron generator-based PGNAA setup (Naqvi et al., 2012a, 2012b). From the measured chloride concentration data from FA, BFS and SPZ cement concrete specimens, a single energy gamma ray with a
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common slope for all concrete types has been determined. The two parts of the study are described in the following sections.
2. Prompt gamma ray analysis of BFS cement concrete specimens The chlorine concentration in BFS cement concrete specimens containing 0.8–3.5 wt% chloride was measured utilizing a portable neutron generator based-PGNAA setup that has been described in detail elsewhere (Naqvi et al., 2012a, 2012b). For continuity, it will also be described in detail here. The PGNAA setup mainly consists of a portable neutron generator, a cylindrical 25 cm 8 cm (diameter x height) high-density polyethylene (HDPE) moderator, a cylindrical 25 cm 14 cm (diameter x height) chlorine-contaminated BFS cement concrete specimen and a cylindrical 5 cm 5 cm (diameter height) BGO gamma ray detector. The concrete specimen was placed on one side of the neutron generator target-plane location, with the axis of symmetry aligned at a right angle to the neutron generator axis. The HDPE moderator was placed between the specimen and the neutron generator with its axis of symmetry aligned with the axis of the concrete specimen. The BGO detector views the concrete specimen at an angle of 451 with respect to its axis of symmetry, as shown in Fig. 1. To prevent undesired gamma rays and neutrons from reaching the detector, lead, tungsten, and paraffin, neutron shielding is inserted between the neutron generator, the moderator and the BGO detector, as shown in Fig. 1. The paraffin neutron shielding is made of a mixture of paraffin and lithium carbonate mixed in equal weight proportions. The cylindrical BFS cement concrete specimens were prepared by mixing 20 wt% BFS as a replacement of cement. The BFS cement concrete
Fig. 1. Schematic of the MP320 portable neutron generator-based PGNAA setup used to measure the prompt gamma-ray yield.
Table 1 Chemical composition (wt%) of Portland and Blended Cements and coarse and fine aggregates Naqvi et al., 2012a, 2012b. Compound
Type V cement
Type I cement
Fly ash
Blast furnace slag
Silica fume
Superpozz
Fine aggregate
Coarse aggregate
SiO2 Al2O3 Fe2O3 CaO CaCO3 MgO SO3 K2O Na2O
22.00 4.08 4.24 64.07 – 2.21 1.96 0.31 0.21
20.52 5.64 3.80 64.35 – 2.11 2.1 0.36 0.19
52.30 25.20 4.6 10.0 – 2.20 0.60 0.10 0.10
27.70 12.80 1.20 44.0 – 8.80 3.10 0.10 0.40
92.50 0.40 0.40 0.50 – 0.90 0.50 0.40 0.10
53.50 34.3 3.6 4.4 – 1.0 – – –
90.70 1.40 0.48 – 5.62 0.26 0.2 0.43 0.17
4.29 0.20 0.23 – 93.20 0.44 0.4 0.09 0.03
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specimens were prepared with 0.8, 2.0, and 3.5 wt% chlorine contamination following a procedure that has been described elsewhere (Naqvi et al., 2012a). The chlorine-contaminated BFS cement concrete specimens were then irradiated in the newly designed portable neutron generator-based PGNAA setup. A pulsed neutron beam of 2.5 MeV was produced via a D(d,n) reaction utilizing a MP320 portable neutron generator. The neutron generator was operated with a 70 keV deuteron beam with a pulse width of 5 ms and a frequency of 250 Hz. The pulsed neutron beam improves the signal-to-background ratio in PGNAA studies. The typical beam current of the generator was 70 μA. The thermal neutron spectra were acquired in a PC-based data acquisition system utilizing multichannel buffer modules. The prompt gamma ray data from chloride-contaminated BFS cement concrete specimens were acquired for 120 min. For background subtraction, the prompt gamma ray data were also acquired from a BFS cement concrete specimen without chloride contamination. Fig. 2 shows interference of full energy (F) and single escape (S) peaks of prompt gamma rays from the BGO detector material and BFS cement concrete specimens containing 0.8, 2.0, and 3.5 wt% chlorine above 2.66 MeV gamma ray energy. These findings are consistent with previously reported observations (Naqvi et al., 2012a, 2012b). The full energy peaks (F) of the prompt gamma rays are marked in Fig. 2. The large peak on the right end of the spectrum is the gamma ray sum peak from activation of the BGO detector, as was observed in previous measurements (Naqvi et al., 2012a, 2012b). For our large-size BGO detector, the sum peak is observed at 7.33 MeV. Several prompt gamma rays are emitted by chlorine due to the capture of thermal neutrons (Naqvi et al., 2012a, 2012b). The chlorine prompt gamma rays with energies in excess of 2.66 MeV were considered in this study. Due to the poor energy resolution of the BGO detector, chlorine prompt gamma rays with energies of 2.86–3.10, 5.72 and 6.11 MeV from BFS cement concrete could be resolved. Fig. 2 shows well-resolved full energy peaks of the concrete constituents in addition to interference between prompt gamma rays from chlorine and prompt gamma rays from the BFS cement concrete constituents and the BGO detector material, as was observed previously (Naqvi et al., 2012a, 2012b). Fig. 2 shows full energy peaks of the concrete constituents at Si (F) 3.54, Si (F) 4.94 and Ca (F) 4.42 MeV (Naqvi et al., 2012a, 2012b). Additionally, Fig. 2 also shows interference between prompt gamma rays from chlorine with prompt gamma rays from the BFS cement concrete constituents and the BGO detector
material (Naqvi et al., 2012a, 2012b). The 6.62–6.63 MeV Cl (F) peak interferes with the 6.42 MeV Ca(F) peak as well as with the 6.71 and 6.72 MeV Ge(F) peaks. The 6.62–6.63 MeV gamma rays from chlorine interfere with the 6.42 and 6.71–6.72 MeV gamma rays from Ge in the BGO detector material (Naqvi et al., 2012a, 2012b). The Cl(F) 6.11 MeV gamma ray, which interferes with the unlabeled Ca(S) 6.42 MeV gamma ray, is quite prominent in Fig. 2. Similarly, the Cl(F) 5.72 MeV gamma ray interferes with the Cl(S) 6.11 MeV gamma ray. An unresolved broad chlorine prompt gamma ray peak has been observed due to the interference of Cl(F) 2.86 and Cl(F) 3.10 MeV (Naqvi et al., 2012a, 2012b). Finally, the chlorine gamma ray yield from each of the chloridecontaminated BFS cement concrete specimens was obtained after subtraction of the normalized prompt gamma ray spectra of pure BFS cement concrete specimen, described elsewhere in detail (Naqvi et al., 2012a, 2012b). Figs. 3 and 4 show the subtracted spectra of chlorine prompt gamma rays over 2.44–4.49 MeV and 4.58–6.63 MeV, respectively, from BFS cement concrete specimens containing 0.8, 2.0, and 3.5 wt% chlorine. Three prominent chlorine full energy gamma ray peaks corresponding to 2.86–3.10, 5.72 and 6.11 MeV energies are clearly shown in Figs. 3 and 4. The counts under each peak were integrated from the spectra of three BFS cement concrete specimens containing different chlorine concentrations. Fig. 5 shows the normalized experimental yield of 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays as a function of chlorine concentration in the BFS cement concrete. Due to strong interference of the Ge peak from the BGO detector and the calcium peak of concrete with the 6.62–6.63 MeV chlorine gamma
Fig. 3. Enlarged prompt gamma-ray experimental pulse height difference spectrum after background subtraction from the three BFS cement concrete specimens, showing full energy prompt gamma-ray peaks at 2.86–3.10 MeV.
Fig. 2. Enlarged experimental pulse height spectra of prompt gamma-rays of chloride-contaminated BFS cement concrete containing 0.8, 2.0 and 3.5 wt% chlorine taken with the BGO detector (The background spectrum taken with uncontaminated BFS cement concrete is also superimposed for comparison purposes).
Fig. 4. Enlarged prompt gamma-ray experimental pulse height difference spectrum after background subtraction from the three BFS cement concrete specimens, showing full energy prompt gamma-rays peaks at 5.72 and 6.11 MeV.
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ray peak, this chlorine peak could not be included in the chlorine analysis. Within the experimental uncertainties, the results are in excellent agreement with the normalized calculated yield of the prompt gamma rays from chlorine in BFS cement concrete (shown with a solid line) obtained through Monte Carlo simulations following a previously described procedure (Naqvi et al., 2012a, 2012b) using the code MCNP4B2 (Briesmeister, 1997). For comparison purposes, Figs. 6 and 7 show the normalized experimental yield of 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays as a function of chlorine concentration in the FA cement concrete specimen (Chichester and Simpson Lemchak) and the SPZ cement concrete specimen (Briesmeister, 1997) reported previously. The minimum detectable concentration (MDC) of chlorine in the BFS cement concrete was calculated using the procedure described in Refs. Naqvi et al., 2012a, 2012b. Table 2 shows the MDC of chlorine in the BFS cement concrete specimens determined by the portable neutron generator-based PGNAA setup for the 2.86–3.10, 5.72 and
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6.11 MeV chlorine prompt gamma rays. Also included in Table 2 are the MDCs of chlorine prompt gamma rays in plain, FA (Naqvi et al., 2012b) and SPZ (Naqvi et al., 2012a) cement concretes obtained utilizing the portable neutron generator-based PGNAA setup. The MDCs of chlorine prompt gamma rays in BFS cement concrete specimens for the portable neutron generator-based PGNAA setup were measured as 0.03470.010, 0.03270.010, 0.03370.010 wt% for 2.86–3.10, 5.72 and 6.11 MeV gamma rays, respectively. Within experimental uncertainties, the MDCs of chlorine in the BFS cement concrete measured for 2.86–3.10, 5.72 and 6.11 MeV gamma rays are in accord. The MDC values measured in the present study are also in accord with the MDC value for 6.11 MeV chlorine prompt gamma rays measured in FA and SPZ cement concretes measured using the portable neutron generator-based PGNAA setup (Naqvi et al., 2012a, 2012b). The maximum permissible chloride concentration in Portland cement concrete according to the American Concrete Institute Committee 318 is 0.03 wt% (ACI Committee 222, 1989). Within statistical uncertainty, the lower bound of the MDC of chlorine measured in the present study meets the maximum permissible limit of 0.03 wt% chloride set by ACI Committee 318 (ACI Committee 222, 1989). Based on the data presented in this study, it can be concluded that the portable neutron generator-based PGNAA setup can be used successfully for the non-destructive determination of chlorine in FA, BFS and SPZ cement concretes. An application has been filed with US Patent Office to register the portable neutron generator-based PGNAA setup for the detection of chlorine in plain and blended concrete structures in the field.
Fig. 5. integrated yields of 2.86–3.1, 5.72 and 6.11 MeV prompt gamma-rays as a function of chlorine concentration for the three BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
Fig. 7. Integrated yields of 2.86–3.10, 5.72 and 6.11 MeV prompt gamma-ray peaks as a function of chlorine concentration in the SPZ cement concrete specimens (Briesmeister, 1997). Solid line represents the calculated yield obtained through Monte Carlo simulations.
Table 2 MDC of chlorine in blended cement concrete using the portable neutron generator based PGNAA setup Naqvi et al., 2012a, 2012b. MDC of Chlorine in Blended Cement Concrete(wt%)
Fig. 6. Integrated yields of 2.86–3.1, 5.72 and 6.11 MeV prompt gamma-rays as a function of chlorine concentration in the FA cement concrete specimens (Chichester and Simpson Lemchak). Solid line represents the calculated yield obtained through Monte Carlo simulations.
Gamma-ray energy (MeV)
BFS Cement concrete (Present study)
FA cement concrete SPZ cement Naqvi et al., 2012b concrete Naqvi et al., 2012a
2.86–3.10 5.72 6.11
0.034 70.010 0.032 70.010 0.03370.010
0.0337 0.010 0.0317 0.010 0.032 7 0.010
0.032 7 0.012 0.0377 0.012 0.0357 0.012
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3. Single prompt gamma ray evaluation for chlorine analysis of FA, BFS and SPZ cement concrete specimens The measured gamma ray yield vs chlorine concentration data for FA, BFS and SPZ cement concrete specimens were sorted separately for each of the 2.86–3.10, 5.72 and 6.11 MeV chlorine gamma rays. Then, each gamma ray yield for the FA, BFS and SPZ cement concretes was plotted against the chlorine concentration (wt%). Figs. 8–10 show the combined yield plot of the FA, BFS and SPZ cement concrete specimens as a function of chlorine concentration for all three gamma rays. The slopes of each of the gamma ray lines for the FA, SPZ and BFS cement concrete specimens are listed in Table 3. Also listed in Table 3 are the correlation coefficients (R2) calculated for the three gamma ray lines. The error in peak counts in the difference spectra was calculated from the square root of the sum of squares of total counts and background counts in the subtracted spectra. The errors in slope and correlation coefficient in the integrated yield vs chlorine concentration were calculated using a standard least square fit. Fig. 8 shows the 2.86–3.10 MeV gamma ray yield vs Cl concentration (wt%) for the FA, SPZ and BFS cement concrete specimens. The slope is 34167500 gamma rays/Cl wt%. There is a large scatter in the data indicated by a relatively poor value of the correlation coefficient (0.83). Fig. 9 shows the 5.72 MeV gamma ray yield vs Cl concentration (wt%) for the FA, SPZ and BFS cement concrete specimens. The slope is 38397192 gamma rays/Cl wt%. There is lesser scatter in the data compared to the 2.86–3.10 MeV gamma
Fig. 8. Integrated yields of 2.86–3.10 prompt gamma-rays as a function of chlorine concentration in FA, SPZ and BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
Fig. 10. Integrated yields of 6.11 MeV prompt gamma-rays as a function of chlorine concentration in FA, SPZ and BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
Table 3 Slope (gamma-ray yield/Cl concentration in wt% ) of gamma rays for combined FA, BFS and SPZ cement concretes specimen. Gamma-ray energy (MeV)
Slope of gamma ray yield ( gamma ray yield /Cl concentration (wt%))
Correlation coefficient R2
2.86–3.10 5.72 6.11
34167 975 3839 7 192 5294 7 171
0.83 0.99 0.99
ray yield data, and the value of the correlation coefficient increased to 0.99. Finally, Fig. 10 shows the 6.11 MeV gamma ray yield vs Cl concentration (wt%) for the FA, SPZ and BFS cement concrete specimens. The slope is 52947171 gamma rays/Cl wt%. There is also less scatter in the data, indicated by the large value of the correlation coefficient (0.99). Out of these three gamma rays, only the 5.72 and 6.11 MeV gamma rays have good correlation and can be used to detect chlorine in blended concrete. Because the 6.11 MeV gamma ray has a larger slope of 52947171 gamma rays/Cl wt% compared to the 5.72 MeV gamma ray, which has a slope of 38397192 gamma rays/Cl wt%., the 6.11 MeV gamma ray is a better choice for detecting chloride in blended concrete. Due to its 38% larger slope than that of the 5.72 MeV gamma ray, the 6.11 MeV gamma ray provides better chlorine detection sensitivity in blended cement concretes.
4. Conclusions
Fig. 9. Integrated yields of 5.72 MeV prompt gamma-rays as a function of chlorine concentration in the FA, SPZ and BFS cement concrete specimens. Solid line represents the calculated yield obtained through Monte Carlo simulations.
The optimum energy of a prompt gamma ray that can be utilized to determine the chloride concentration in fly ash, blast furnace slag and Super-Pozz cement concretes utilizing a portable neutron generator-based PGNAA setup has been evaluated. The chlorine concentration in BFS cement concrete was measured using 2.86–3.10, 5.72 and 6.11 MeV chlorine prompt gamma rays. The minimum detected concentrations (MDCs) of chlorine in BFS cement concrete were found to be 0.034 7 0.010, 0.0327 0.010, 0.03370.010 for 2.86–3.10, 5.72 and 6.11 MeV gamma rays, respectively. The slopes of gamma ray yield vs chlorine concentration curves for the three blended cement concrete specimens were compared for each of the three (2.86–3.10, 5.72 and 6.11 MeV) chlorine gamma rays. The gamma ray with the maximum value of common slope (gamma ray yield/Cl conc. wt%) for all the three concrete specimens was identified. It was determined that 6.11 MeV chlorine gamma ray has the best sensitivity for the detection of chlorine
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in blended cement concrete because the value of the slope of gamma ray yield vs chlorine concentration is 38% more than that of the 5.72 MeV gamma ray. Thus, the 6.11 MeV gamma ray can be used for the chlorine analysis of FA, SPZ and BFS concrete specimens with the portable neutron generator-based PGNAA setup. The results of this study show that the portable neutron generator can be utilized for evaluating the chloride contamination in concrete in the field using 6.11 MeV chlorine prompt gamma rays. Acknowledgments The study is part of project ♯ RG1008 funded by the King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia. The support provided by the Department of Physics, Center for Engineering Research and Department of Civil and Environmental Engineering at KFUPM is also acknowledged. References ACI Committee 222, 1989. (ACI 222R-89). Corrosion of Metals in Concrete. American Concrete Institute, Detroit, USA.
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Al-Amoudi, O.S.B., 2002. Durability of Plain and Blended Cements in Marine Environments (July). Adv. Cement Res. 14 (3), 89–100. Al-Amoudi, O.S.B., Maslehuddin, M., Bader, M.A., 2001. Characteristics of silica fume and its impact on concrete in the Arabian Gulf (February). Concrete 35 (2), 45–50. Briesmeister J.F. (Ed). MCNP4B2 –A General Monte Carlo N-Particles Transport Code. Los Alamos National Laboratory Report, LA-12625. Version 4A. Los Alamos National Laboratory Report, LA-12625-M, 1997. Chichester, D.L., J.D. Simpson and M. Lemchak, Advanced compact accelerator neutron generator technology for active neutron interrogation field work, Journal of Radio Analytical and Nuclear Chemistry, 271, 629–637, 2007. Gardner, R.P., El, Sayyed, Yuanshui, Zheng, Hayden, S., Mayo, C.W., 2000. NaI detectors activation spectra for PGNAA applications. Appl. Radiat. Isot. 53, 483–497. Maslehuddin, M., Page, C.L., Rasheeduzzafar, 1996. J. Mater. Civil Eng. 8, 63. Naqvi, A.A., Kalakada, Zameer, Al-Matouq, Faris A., Maslehuddin, M., Al-Amoudi, O. S.B., 2012a. Prompt gamma ray analysis of chlorine in superpozz cement concrete. Nucl. Inst. Methods Phys. Res., A 693, 67–73. Naqvi, A.A., Kalakada, Zameer, Al-Matouq, Faris A., Maslehuddin, M., Al-Amoudi, O. S.B., 2012b. Chlorine detection in fly ash concrete using a portable neutron generator. Appl. Radiat. Isot. 70, 1671–1674. PCI Committee, 1994. Guide to using silica fume in precast/prestressed concrete products (September–October). PCI J. 39 (5), 36–45. Paul, R.L., Lindstrom, R.M., 2000. Prompt gamma ray activation analysis: fundamentals and applications. J. Radioanal. Nucl. Chem. 243, 181–189. Saleh, H.H., Livingston, R.A., 2000. Experimental evaluation of a portable neutronbased gamma-spectroscopy system for chloride measurements in reinforced concrete. J. Radioanal. Nucl. Chem. 244, 367.
