- Email: [email protected]
The influences of maximum aggregate size and cement content on the mechanical and radiation shielding characteristics of heavyweight concrete
Progress in Nuclear Energy 121 (2020) 103222
Contents lists available at ScienceDirect
Progress in Nuclear Energy journal homepage: http://www.elsevier.com/locate/pnucene
The influences of maximum aggregate size and cement content on the mechanical and radiation shielding characteristics of heavyweight concrete Omid. Lotfi-Omran a, Ali. Sadrmomtazi a, *, Iman.M. Nikbin b a b
Department of Civil Engineering, University of Guilan, Rasht, Iran Department of Civil Engineering, Rasht Branch, Islamic Azad University, Rasht, Iran
A R T I C L E I N F O
A B S T R A C T
Keywords: Heavyweight concrete Magnetite Radiation shielding Maximum aggregate size Cement content Protective properties
Nowadays, heavyweight concrete (HWC) is considered as one of the best materials for shielding against nuclear radiations due to its high density and good structural properties. On the other hand, cement content, aggregates and water to cement (w/c) ratio are the effective factors on the concrete behavior. Thus, in this investigation, the influences of cement content (c ¼ 350, 400 kg/m3), maximum aggregate size (MAS ¼ 12.5, 19, 25 mm) and w/c ratio (w/c ¼ 0.45, 0.65) on the shielding characteristics of heavyweight magnetite concrete against gamma-ray radiation were investigated. The protecting parameters which were assessed in this study are linear attenuation coefficient (LAC), mean free path (mfp), tenth value layer (TVL) and half value layer (HVL). The radiation sources of Cs137 and Co60 with photon energies of 0.662, 1.173 and 1.333 MeV were used. The results indicated that with the increase of MAS and decrease of cement content and w/c ratio, the passing flux will be reduced and shielding characteristics of heavyweight magnetite concrete will be improved.
1. Introduction Due to the wide utilization of nuclear technology for different pur poses in industry and medical uses, shielding against these hazardous radiations which have harmful environmental impacts seems necessary (Singh et al., 2004; Salinas et al., 2006; Akkurt et al., 2010). Because of appropriate structural properties, concrete is considered as one of the best materials for shielding against radiations. Particularly, with increasing concrete density using heavyweight aggregates, the thickness of protective members will be decreased and shielding characteristics of concrete will be enhanced considerably (Havranek, 1971; Neville, 1996; Acevedo and Serrato, 2010; Gencel et al., 2010, 2011; Demir et al., 2011; Yılmaz et al., 2011; Akkurt et al., 2012). According to ACI defi nition (ACI 304.3R, 2001), the density of heavyweight concrete (HWC) is more than 2600 kg/m3 and approximately the same relations for design of normal concrete can be used for it (BS 8500, 2006; Sagar Singh and Ramana, 2014). HWC is used in nuclear facilities for shielding against gamma or X-radiations or other places with the transmission possibility of radioactive radiations. The production of HWC is more expensive than normal concrete (Sagar Singh and Ramana, 2014). With the increase of concrete density, its mechanical properties will be altered
(Yang et al., 2014). Various investigations have been performed on the impact of heavyweight aggregates such as magnetite (Sharifi et al., 2013; Yang et al., 2014; Horszczaruk et al., 2015; Oto et al., 2016), hematite (Mesbahi et al., 2011), limonite (Oto et al., 2015; Esen and �an, 2018), lead-zinc (Rezaei-Ochbelagh and Azimkhani, 2012; Ç ullu Dog and Ertas, 2016; Alwaeli, 2017; Ç ullu and Bakırhan, 2018; Tijani et al., 2018), colemanite (Demir et al., 2010), barite (Esen and Yilmazer, 2010, 2011; Jankovic et al., 2016; Junior et al., 2017) and goethite (Ouda, 2015) on the attenuation of radioactive radiations. Generally, concrete is a three-phase material including cement paste, aggregates, and interfacial transition zone (ITZ) (Kang, 2010; Konigsberger et al., 2014a; €nigsberger et al., 2014b). Since aggregates occupy 70% of the con Ko crete volume, the mechanical properties of concrete are strongly dependent on them (Moavenzadeh and Kuguel, 1969; Feng et al., 1995; Amparano et al., 2000; Chen and Liu, 2004). In addition, various investigations have been performed on the in fluence of w/c ratio (Ince and Alyamac, 2008), size (Tasdemir et al., 1996; Amparano et al., 2000; Chen and Liu, 2004; Elices and Rocco, 2008; Grassl et al., 2010; Beygi et al., 2014a; Al-khazraji et al., 2017), type, shape, and texture (Xiao et al., 2004; Li et al., 2004; Appa Rao and Raghu Prasad, 2011; Hong et al., 2014; Vishalakshi et al., 2018), volume
* Corresponding author. E-mail addresses: [email protected] (Omid. Lotfi-Omran), [email protected], [email protected] (Ali. Sadrmomtazi), Nikbin@ iaurasht.ac.ir, [email protected] (Iman.M. Nikbin). https://doi.org/10.1016/j.pnucene.2019.103222 Received 29 July 2019; Received in revised form 21 October 2019; Accepted 20 December 2019 Available online 13 January 2020 0149-1970/© 2019 Elsevier Ltd. All rights reserved.
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Table 1 The mix designs concrete samples utilized in the present research. MAS (mm)
w/c
c (kg/m3)
Mix.ID
Sand (kg/m3)
4.75–12.5 (mm)
4.75–19 (mm)
4.75–25 (mm)
12.5
0.45
350 400 350 400
D12.5W0.45C350 D12.5W0.45C400 D12.5W0.65C350 D12.5W0.65C400
1825.3 1726.5 1664 1542.3
1444 1366 1316.5 1220.1
– – – –
– – – –
3783.9 3680.6 3558 3422.4
350 400 350 400
D19W0.45C350 D19W0.45C400 D19W0.65C350 D19W0.65C400
1829.4 1730.4 1667.8 1545.7
– – – –
1447.3 1369 1319.4 1223
– – – –
3791.2 3687.5 3564 3428.7
350 400 350 400
D25W0.45C350 D25W0.45C400 D25W0.65C350 D25W0.65C400
1850.5 1750.4 1687 1563.5
– – – –
– – – –
1464 1384.4 1334.6 1237
3829.1 3723.3 3599.2 3460.5
0.65
19
0.45 0.65
25
0.45 0.65
Coarse Aggregate (kg/m3)
fraction of aggregates (Beygi et al., 2014b; Ackay et al., 2012), aggregate size distribution (Wu et al., 2001) and ITZ (Guinea et al., 2002; €nigsberger et al., 2014b) on the me Konigsberger et al., 2014a; Ko chanical and fracture characteristics of concretes. Uddin et al. (2017) found that for low cement content, concrete compressive strength in creases with increasing maximum aggregate size (MAS). Aïtcin (2011) showed that ITZ quality drops with increasing MAS which leads to the reduction of mechanical characteristics of concrete. However, Vu et al. (2011) reported improvement of concrete compressive strength with increasing MAS. Meddah et al. (2010) and Kobir Hossain et al. (2015) depicted that with increasing MAS, compressive strength of concrete increases. Ezeldin and Aitcin (1991) stated that aggregate size does not affect concrete behavior. There are different investigations on the application of heavyweight aggregates in concrete. Esen and Do� gan (2018) showed that increase of heavyweight limonite aggregates results in the reduction of tensile, flexural and compressive strengths and radiation permeability of con crete and increase of its water absorption. Ç ullu and Bakırhan (2018) showed that strength grade of concrete affects the coefficient of radia tion absorption in heavyweight lead-zinc concretes. The results of studies indicated that application of barite powder (Saidani et al., 2015) and barite aggregates (Gonzalez-Ortega et al., 2015) in heavyweight concrete for the purpose of shielding against ultraviolet (UV) radiations in nuclear facilities and hospitals resulted in the decrease of concrete mechanical properties. However, heavyweight magnetite concrete showed better mechanical properties and radiation attenuation power than heavyweight concretes made by barite and goethite (Ouda, 2015). Jankovic et al. (2016) found that utilization of barite aggregates leads to the decrease of compressive strength and increase of flexural strength. Oto et al. (2016) concluded that the performance of heavyweight magnetite concrete in attenuation of gamma and neutron rays has been acceptable. In addition, Al-Humaiqani et al. (2013a) and Al-Humaiqani et al. (2013b) depicted that linear relationship exists between gamma-ray attenuation and compressive strength in high performance concrete (HPC). The influences of w/c ratio and cement paste volume on the ordinary concrete have been investigated previously (Kolias and Georgiou, 2005;
Unit Weight (kg/m3)
Elsharief et al., 2003). Tracz and Sliwinski (2012) and Sliwinski and Tracz (2013) found that with increasing cement paste volume, water absorption and compressive strength of concrete increases and de creases, respectively. Similar results were reported for lightweight concrete (Talaei et al., 2014). Regarding literature, the effects of MAS, w/c ratio and cement con tent on the mechanical properties of different types of concretes have been assessed in previous studies. In this research, due to the lack of comprehensive investigations, it has been attempted to explore the in fluences of MAS, w/c ratio and cement content on the mechanical characteristics (compressive strength, tensile strength, modulus of elasticity) and also shielding parameters (linear attenuation coefficient, mean free path, tenth value layer and half value layer) of heavyweight magnetite concrete. 2. Experimental program 2.1. Materials In this investigation, magnetite aggregates from Chadormalu mines located in the Yazd Province of Iran were employed for preparation of the HWC specimens. For magnetite gravel, three different maximum aggregate sizes (MAS) of 12.5, 19 and 25 mm with specific gravity of 4.39, 4.41 and 4.43, respectively, were provided. Moreover, magnetite sand with a fineness modulus of 3.3 and type II Neka Portland cement were utilized. In order to prevent the impact of water absorption of aggregates during mixing procedure and to evaluate the real influence of aggregates on the concrete characteristics, the aggregates were utilized in a saturated surface dry condition. In all mixes, a polycarboxylatebased superplasticizer was used for appropriate workability properties. 2.2. Mixture design Totally, 12 mixing designs including three maximum aggregate sizes (MAS ¼ 12.5, 19 and 25 mm), two cement contents (c ¼ 350 and 400 kg/ m3) and two water to cement ratios (w/c ¼ 0.45 and 0.65) were considered in this research (Table 1).
2
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 1. (a): Test process (b): schematic view of experimental set up for measurement of radiation attenuation.
3
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 2. A linear fit for determination of the LAC values (for mix D25W0.45C350 at different energy levels).
4
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 3. Variation of fc with MAS, cement content and w/c ratio.
Table 2 The obtained mechanical properties for various MAS, cement contents and w/c ratios. Mix.ID
MAS (mm)
w/c
c (kg/m3)
fc (MPa)
E (GPa)
ft (MPa)
Density (kg/m3)
D12.5W0.45C350 D12.5W0.45C400 D12.5W0.65C350 D12.5W0.65C400
12.5
0.45
350 400 350 400
55.9 63.3 31.8 36.6
36.1 36.6 29.6 32.7
4.75 5.06 3.5 4.1
3783.9 3680.6 3558 3422.4
D19W0.45C350 D19W0.45C400 D19W0.65C350 D19W0.65C400
19
350 400 350 400
57.5 62.8 31.2 35.2
36.33 36.17 29.3 32.4
4.65 4.91 3.1 3.6
3791.2 3687.5 3564 3428.7
D25W0.45C350 D25W0.45C400 D25W0.65C350 D25W0.65C400
25
350 400 350 400
60.1 62.4 31.15 32.7
36.6 36.04 29.18 31.9
4.43 4.87 3 3.6
3829.1 3723.3 3599.2 3460.5
0.65
0.45 0.65
0.45 0.65
2.3. Specimens preparation and test methods
test, respectively. Using Beer-Lambert’s law, the parameter LAC (linear attenuation coefficient) can be determined (Wood, 2013):
2.3.1. Mechanical properties For each experimental series of tests, four cubes with dimensions of 10 � 10 � 10 cm were prepared to obtain the compressive strength (fc) based on BS EN 12390 (2000) and six standard cylinders with di mensions of 15 � 30 cm were tested to achieve splitting tensile strength (ft) and modulus of elasticity (E) and based on ASTM C496 (2017) and ASTM C469 (2014), respectively. The prepared samples were cured under water with the temperature of approximately 20 � C for 28 days.
1 D0 LAC ¼ ln t D
(1)
In Eq. (1), D0 and D are the background subtracted number of counts recorded in detector without and with an absorbent material between detector and source, respectively, and t is the thickness of material. As observed in Fig. 2, LAC is the slope of the straight line obtaining by drawing variation of each ln (D0/D) with thickness (t). TVL (tenth value layer) and HVL (half value layer) are used for determination of radiation shielding effectiveness. TVL and HVL are defined as the thicknesses of an absorber that can decrease the radiation of gamma to tenth and to half of its intensity, respectively (Akkurt and Canakci, 2011):
2.3.2. Gamma-ray attenuation test For gamma ray attenuation test, a 3 ʺ � 3 ʺ sodium iodide scintilla tion NaI (T1) detector with a multi-channel analyzer was employed in this investigation. The radiation sources of Cs137 and Co60 with energies of 0.662, 1.173 and 1.333 MeV were used. The 30 � 30 � 6 cm concrete specimens with various thicknesses (t) of 6–24 cm were placed in front of a collimated beam emerged from radiation sources. Fig. 1(a) and (b) illustrate process and schematic arrangement of concrete samples in the
5
TVL ¼ ln 10=LAC
(2)
HVL ¼ ln 2=LAC
(3)
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 4. Variation of ITZ with MAS.
Fig. 5. Relation between fc, cement content and MAS.
6
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 6. Variation of ft with MAS, cement content and w/c ratio.
Fig. 7. Variation of E with MAS, w/c ratio and cement content.
7
6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24
D12.5W0.45C350
8
D25W0.65C400
D25W0.65C350
D25W0.45C400
D25W0.45C350
D19W0.65C400
D19W0.65C350
D19W0.45C400
D19W0.45C350
D12.5W0.65C400
D12.5W0.65C350
D12.5W0.45C400
t (cm)
Mix.ID 705322 � 1323 137361 � 802 27811 � 151 5148 � 89 701289 � 3666 158444 � 12 30130 � 960 6683 � 440 705311 � 1250 159810 � 416 31001 � 622 7010 � 80 729932 � 3232 171108 � 210 35218 � 870 16520 � 342 655434 � 3407 123599 � 583 22847 � 343 4813 � 94 693216 � 2544 154318 � 899 29731 � 464 5456 � 777 700315 � 1475 154683 � 691 29751 � 68 6196 � 150 725329 � 1530 170931 � 560 34622 � 177 13402 � 85 623101 � 2587 127410 � 713 19853 � 275 2741 � 150 651255 � 2006 133791 � 708 25010 � 459 4298 � 181 706517 � 233 140129 � 968 28001 � 72 5298 � 545 715140 � 2451 162399 � 982 33413 � 312 8731 � 17
D
Ln(D0/D) 0.10 1.74 3.34 5.02 0.11 1.60 3.26 4.76 0.10 1.59 3.23 4.72 0.07 1.52 3.10 3.86 0.18 1.85 3.53 5.09 0.12 1.62 3.27 4.97 0.11 1.62 3.27 4.84 0.08 1.52 3.12 4.07 0.23 1.81 3.67 5.66 0.18 1.77 3.44 5.20 0.10 1.72 3.33 4.99 0.09 1.57 3.15 4.50
Table 3 The obtained radiation test results for different MAS, cement contents and w/c ratios (Cs137 -662 keV source).
0.201
0.220
0.227
0.246
0.182
0.214
0.218
0.225
0.179
0.209
0.211
0.221
LAC (cm
1
)
HVL (cm)
3.44
3.15
3.05
2.81
3.80
3.23
3.18
3.08
3.87
3.31
3.28
3.13
TVL (cm)
11.45
10.46
10.14
9.36
12.65
10.75
10.56
10.23
12.86
11.01
10.91
10.41
mfp (cm)
4.97
4.54
4.40
4.06
5.50
4.67
4.58
4.44
5.58
4.78
4.74
4.52
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24
D12.5W0.45C350
9
D25W0.65C400
D25W0.65C350
D25W0.45C400
D25W0.45C350
D19W0.65C400
D19W0.65C350
D19W0.45C400
D19W0.45C350
D12.5W0.65C400
D12.5W0.65C350
D12.5W0.45C400
t (cm)
Mix.ID 42530 � 522 12246 � 3 3597 � 751 1050 � 2 45289 � 135 4571 � 111 4347 � 658 1562 � 4 46113 � 410 15261 � 97 5274 � 209 2098 � 44 46815 � 161 15731 � 52 5412 � 455 2434 � 749 42201 � 318 11942 � 45 3388 � 171 873 � 180 45240 � 261 14620 � 413 4363 � 242 1456 � 81 45720 � 858 14584 � 309 5074 � 230 1920 � 11 45902 � 66 14691 � 87 5205 � 45 2019 � 540 39932 � 112 1052 � 74 2897 � 560 419 � 22 43818 � 797 12853 � 325 3702 � 668 1314 � 7 43467 � 411 14123 � 569 4368 � 82 1636 � 12 45600 � 230 14167 � 188 4675 � 181 1709 � 16
D
Ln(D0/D) 0.95 2.19 3.42 4.65 0.89 2.00 3.23 4.25 0.87 1.97 3.04 3.96 0.85 1.94 3.01 3.81 0.95 2.22 3.48 4.83 0.89 2.02 3.22 4.32 0.87 2.02 3.07 4.04 0.87 2.01 3.05 4.00 1.01 2.35 3.63 5.56 0.92 2.14 3.39 4.42 0.93 2.05 3.22 4.20 0.88 2.05 3.15 4.16
Table 4 The obtained radiation test results for different MAS, cement contents and w/c ratios (Co60 -1173 keV source).
0.176
0.178
0.188
0.229
0.169
0.171
0.182
0.203
0.163
0.168
0.180
0.196
LAC (cm
)
1
HVL (cm)
3.93
3.90
3.68
3.02
4.10
4.05
3.80
3.41
4.25
4.12
3.85
3.53
TVL (cm)
13.08
12.93
12.24
10.05
13.62
13.46
12.65
11.34
14.12
13.70
12.80
11.74
mfp (cm)
5.68
5.61
5.32
4.36
5.91
5.84
5.50
4.92
6.13
5.95
5.55
5.10
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24
D12.5W0.45C350
10
D25W0.65C400
D25W0.65C350
D25W0.45C400
D25W0.45C350
D19W0.65C400
D19W0.65C350
D19W0.45C400
D19W0.45C350
D12.5W0.65C400
D12.5W0.65C350
D12.5W0.45C400
t (cm)
Mix.ID 55081 � 684 16799 � 218 4847 � 264 1046 � 279 57063 � 535 18944 � 308 5981 � 112 1940 � 201 58813 � 144 20466 � 499 7645 � 315 2470 � 223 58812 � 684 19730 � 218 7682 � 264 2911 � 279 54018 � 409 16259 � 64 4391 � 623 1080 � 24 57091 � 104 18840 � 836 5964 � 47 1798 � 42 58779 � 144 21722 � 499 7044 � 315 2314 � 223 58815 � 409 19938 � 64 7351 � 623 2587 � 24 52801 � 409 15576 � 64 4028 � 623 749 � 24 55320 � 731 17259 � 177 4978 � 283 1604 � 346 57222 � 228 19630 � 224 6022 � 316 2002 � 122 57401 � 535 20664 � 308 6601 � 112 2181 � 201
D
Ln(D0/D) 0.86 2.04 3.29 4.82 0.82 1.92 3.08 4.20 0.79 1.85 2.83 3.96 0.79 1.88 2.83 3.80 0.88 2.08 3.39 4.79 0.82 1.93 3.08 4.28 0.79 1.79 2.91 4.03 0.79 1.87 2.87 3.92 0.90 2.12 3.47 5.15 0.85 2.02 3.26 4.39 0.82 1.89 3.07 4.17 0.81 1.84 2.98 4.09
Table 5 The obtained radiation test results for different MAS, cement contents and w/c ratios (Co60 -1333 keV source).
0.172
0.176
0.186
0.214
0.165
0.169
0.180
0.201
0.160
0.166
0.177
0.201
LAC (cm
)
1
4.02
3.93
3.72
3.24
4.20
4.10
3.85
3.44
4.33
4.17
3.91
3.44
HVL (cm)
13.87
13.08
12.38
10.76
13.95
13.62
12.80
11.45
14.40
13.87
13.00
11.45
TVL (cm)
5.81
5.68
5.37
4.67
6.00
5.91
5.55
4.97
6.25
6.02
5.65
4.97
mfp (cm)
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 8. Variation of LAC with MAS, cement content and w/c ratio (for Cs137 and Co60 radioactive sources).
11
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 9. Relation between LAC and density (for different MAS, cement contents and w/c ratios).
The parameter mfp (mean free path) is the average distance between two successive interactions of photons and calculated as: mfp ¼ 1=LAC
w/c ratio, size of aggregate and cement to aggregate ratio. Since these factors are not independent from each other, the role of aggregates is not very obvious (Elices and Rocco, 2008). Meddah et al. (2010) showed that concrete compressive strength improves with increasing MAS. Wu et al. (2001) concluded that concrete compressive strength rises with increasing MAS up to 15 mm and reduces beyond this size. Fig. 5 shows variation of fc with MAS and the comparison of the results found in this investigation with the results of previous investigations.
(4)
3. Results and discussions 3.1. Compressive strength Fig. 3 and Table 2 depict the effects of MAS, cement content and w/c ratio on the compressive strength (fc). It can be observed that for low cement content and w/c ratio values (c ¼ 350 kg/m3 and w/c ¼ 0.45), compressive strength increases with increasing MAS from 12.5 to 25 mm. It can be related to two reasons: 1- For low cement content (c ¼ 350 kg/m3), the role of aggregates will be more considerable and the bridging effect in the cement matrix will be improved. Thus, more energy is required for fracture of concrete specimens. 2-According to Fig. 4, the perimeter of ITZ decreases with increasing MAS (Mohammed and Mahmood, 2016; Uddin et al., 2017). Hence, at the cement content of 350 kg/m3, ITZ quality will be enhanced and the possibility of internal bleeding will be reduced with the increase of MAS. However, with the increase of MAS for high cement content (c ¼ 400 kg/m3), the excess amount of cement paste leads to the separation be tween aggregates, increase of the internal bleeding possibility and reduction of compressive strength. Piasta and Zarzycki (2017) found that for HPC, compressive strength and water absorption decrease with the increase of w/c ratio and volume of cement paste. Kolias and Georgiou (2005) concluded that concrete strength is dependent on ITZ,
3.2. Tensile strength and modulus of elasticity Fig. 6 and Table 2 illustrate variation of the tensile strength (ft) of heavyweight magnetite concrete with MAS, cement content and w/c ratio. It can be observed that with increasing MAS, tensile strength re duces which this issue is more considerable for higher w/c ratio (w/c ¼ 0.65). Elsharief et al. (2003) stated that with the increase of MAS, more water will be present in the cement paste. Thus, the porosity increases and ITZ quality drops and since tensile strength is strongly dependent on ITZ, this strength decreases. Some other researchers also reported reduction of ft with the increase of MAS (Saouma et al., 1991; Tasdemir et al., 1996; Akcaoglu et al., 2004). Fig. 7 and Table 2 illustrate the influences of MAS, cement content and w/c ratio on the modulus of elasticity (E) which is similar to Fig. 3. Tasdemir et al. (1996) and Uddin et al. (2017) also found similar results. 3.3. Gamma-ray radiation shielding Tables 3–5 present the measured protecting parameters (LAC, HVL, TVL, mfp) of heavyweight magnetite concrete containing different MAS, 12
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 10. Variation of LAC with density (for Co60 and Cs137 radioactive sources).
13
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 11. Variation of the LAC with fc (for Co60 and Cs137 radioactive sources).
14
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 12. Gamma-ray energy spectrum of heavyweight magnetite concrete with different MAS and without an absorbent material (background).
cement contents and w/c ratios. According to Tables 3–5 and Fig. 8, it is obvious that LAC improves with the increase of MAS and reduction of cement content and w/c ratio. With increasing MAS, the possibility of radiation interaction with concrete increases and consequently LAC rises. It can be observed that at c ¼ 400 kg/m3 and w/c ¼ 0.65, LAC improves 12.3, 7.9 and 7.5% with increasing MAS from 12.5 to 25 mm for energies of 0.662, 1.173 and 1.333 MeV, respectively. By reducing cement content and w/c ratio, LAC increases too. For example, at Cs137 -0.662 MeV, the LAC of the mix D12.5W0.45C350 is 23.5% greater than LAC of the mix D12.5W0.65C400. In addition, for the same level of energy (Cs137 -0.662 MeV), the LAC of the mix D25W0.45C350 is 37.4% greater than LAC of the mix D12.5W0.65C400 that indicates the com bined influences of MAS, w/c ratio and cement content on the LAC. In addition, it can be observed that with increasing energy level from 0.662 to 1.333 MeV, concrete samples can absorb less radiation and LAC will be reduced. In order to compensate this effect, the shielding con crete thickness should be increased. The variation of LAC with photon energy is due to the variation of absorption mechanism and interaction of photon with shielding material. For energy levels of low, medium and high (more than 1.022 MeV), the interaction mechanism is mainly photoelectric phenomenon, Compton scattering and pair production, respectively (Akkurt et al., 2005). Since the mixture calculation of the specimens was conducted considering volume, density of heavyweight magnetite concrete in creases with increasing MAS from 12.5 to 25 mm. With the reduction of cement content, the role of heavyweight magnetite aggregates becomes more considerable which leads to the higher growth of density (Fig. 9). It is worth remarking that porosity of cement paste and ITZ decreases with reducing w/c ratio. This issue results in the increase of density and enhancement of concrete microstructure. Therefore, passing flux de creases and LAC increases. Singh et al. (2015) and Junior et al. (2017) found similar results. Fig. 10 shows the relations between LAC and density using linear
regression and the comparison of the results with other previous in vestigations. It is obvious that for all three energy levels, LAC increases with increasing density. As observed in Fig. 11, for c ¼ 350 kg/m3 and w/c ¼ 0.45, LAC and compressive strength increase with increasing MAS from 12.5 to 25 mm. It can be related to the fact that at low w/c ratio, the microstructure of cement paste and ITZ improve that leads to the improvement of LAC and fc. With increasing cement content in volume mix design, the role of aggregates in concrete becomes less which results in the decrease of density and LAC. 3.4. Energy spectrums It is obvious in Fig. 12 that for c ¼ 350 kg/m3 and w/c ¼ 0.45, passing flux decreases in presence of the heavyweight magnetite con crete and this reduction becomes more considerable with increasing MAS (for all three levels of energy). As mentioned previously, LAC re duces with increasing energy. Thus, the photon absorption values of samples for 0.662 MeV have been more than other two energy levels. 3.5. Effect of thickness Fig. 13 depicts variation of LAC with thickness (t) of heavyweight magnetite concrete samples at 0.662, 1.173 and 1.333 MeV energy levels. It can be concluded that due to the higher interaction of gamma radiations with concrete, LAC increases with increasing concrete thickness which this effect is more remarkable for Cs137 source. 3.6. mfp As observed in Fig. 14, mfp decreases with the reduction of w/c ratio and cement content and increase of MAS. It can be concluded that by performing variations in the constituents of heavyweight magnetite concrete, energy can be attenuated in less distance and thus, less
15
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 13. Variation of LAC with thickness of heavyweight magnetite concrete specimens (for Co60 and Cs137 sources).
16
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 14. Variation of mfp with the photon energy for different MAS, cement contents and w/c ratios.
concrete thickness will be required. Moreover, it is clear that less dis tance is needed for attenuation of lower energy level (0.662 MeV). However, for higher energy level (1.333 MeV), more distance is required for energy attenuation.
1 At low cement content, the compressive strength and modulus of elasticity of heavyweight magnetite aggregate improve with the in crease of MAS. However, a decreasing trend was observed for high cement content. With the increase of MAS, ITZ quality drops. Since value of concrete tensile strength strongly depends on ITZ, this value decreases with increasing MAS. This trend was seen for all cement contents and w/c ratios. 2 With the increase of MAS and the reduction of w/c ratio and cement content, LAC increased. For c ¼ 400 kg/m3 and w/c ¼ 0.65, LAC increases 12% with increasing MAS from 12.5 to 25 mm and for c ¼ 350 kg/m3 and w/c ¼ 0.45, LAC improves 22% with increasing MAS from 12.5 to 25 mm (at the energy level of 0.662 MeV). 3 For all three levels of energy, with the increase of MAS and the reduction of w/c ratio and cement content, concrete density and LAC increase. In addition, with the increase of energy level from 0.662 to 1.333 MeV, the passing flux increases and LAC decreases. In order to compensate this effect, the thickness of the shielding concrete should be increased. For a constant cement content and w/c ratio, the passing flux decreases with increasing MAS from 12.5 to 25 mm for all three levels of energy. 4 The transmission rate decreases with increasing MAS and decreasing cement content and w/c ratio. Thus, HVL and TVL values will be reduced. For instance, for D25W0.45C350, HVL and TVL values are 25, 28 and 27% lower than D12.5W0.65C400 HVL and TVL ones for Co60 -1333, Co60 -1173 and Cs137 -662 keV, respectively.
3.7. HVL and TVL The transmission rate of gamma-ray is one of the effective factors that can specify the required thickness of an absorbent material to stop gamma-ray. From this viewpoint, HVL and TVL are two protecting pa rameters which show absorber thickness that decrease the transmission rate of gamma-ray to half and tenth, respectively. As observed in Fig. 15, the transmission rate reduces with the increase of MAS and the decrease of w/c ratio and cement content that consequently leads to the reduction of HVL and TVL. For instance, for D25W0.45C350, HVL and TVL values are 25, 28 and 27% lower than D12.5W0.65C400 ones for Co60 -1333, Co60 -1173 and Cs137 -662 keV, respectively. With increasing MAS of heavyweight magnetite aggregates and reducing cement content, the concrete density improves. In addition, with decreasing w/c ratio, the quality of ITZ and cement paste will be enhanced which increases pos sibility of gamma-ray interaction with concrete and reduces the required concrete thickness for radiation attenuation. This issue can be applied for places where there is not enough space for construction of shielding concrete wall.
Finally, it can be concluded that for places with limit of enough space for construction of shielding concrete, the thickness of heavyweight magnetite concrete can be reduced by increasing MAS and decreasing w/c ratio and cement content.
4. Conclusions Since aggregates, cement content and w/c ratio are known as the principal factors influencing concrete behavior, the impacts of these factors on the mechanical and shielding characteristics of heavyweight magnetite concrete have been explored in this experimental research. The following results can be drawn based on the present study:
17
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 15. Variation of transmission rate with thickness (for Co60 and Cs137 sources).
18
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Appendix A. Supplementary data
Feng, N.Q., Ji, X.H., Zhuang, Q.F., Ding, J.T., 1995. Effect of concrete materials on fracture performance. In: Wittmann, F.H. (Ed.), Fracture Mechanics of Concrete Structures, Proc. Of FRAMCOS-2.D-79104 Freiburg. Aedificatio Publishers, pp. 119–124. Gencel, O., Bozkurt, A., Kam, E., Korkut, T., 2011. Determination and calculation of gamma and neutron shielding characteristics of concretes containing different hematite proportions. Ann. Nucl. Energy 38, 2719–2723. Gencel, O., Brostow, W., Ozel, C., Filiz, M., 2010. An investigation on the concrete properties containing colemanite. Int. J. Phys. Sci. 5, 216–225. Gonzalez-Ortega, M.A., Cavalaro, S.H.P., Aguado, A., 2015. Influence of barite aggregate friability on mixing process and mechanical properties of concrete. Constr. Build. Mater. 74, 169–175. Grassl, P., Wong, H.S., Buenfeld, N.R., 2010. Influence of aggregate size and volume fraction on shrinkage induced micro-cracking of concrete and mortar. Cement Concr. Res. 40, 85–93. Guinea, G.V., El-Sayed, K., Rocco, C.G., Elices, M., Planas, J., 2002. The effect of the bond between the matrix and the aggregates on the cracking mechanism and fracture parameters of concrete. Cement Concr. Res. 32, 1961–1970. Havranek, M., 1971. The calculation of the total dose in concretes for radiation shielding design. Nucl. Eng. Des. 16, 249–252. Hong, L., Gu, X., Lin, F., 2014. Influence of aggregate surface roughness on mechanical properties of interface and concrete. Constr. Build. Mater. 65, 338–349. Horszczaruk, E., Sikora, P., Zaporowski, P., 2015. Mechanical properties of shielding concrete with magnetite aggregate subjected to high temperature. Procedia Eng 108, 39–46. Ince, R., Alyamac, K.E., 2008. Determination of fracture parameters of concrete based on the water-cement ratio. Indian J. Eng. Mater. Sci. 15, 14–22. Jankovic, K., Stankovic, S., Bojovic, D., Stojanovic, M., Antic, L., 2016. The influence of nano-silica and barite aggregate on properties of ultra high performance concrete. Constr. Build. Mater. 126, 147–156. Junior, T.A.A., Nogueira, M.S., Vivolo, V., Potiens, M.P.A., Campos, L.L., 2017. Mass attenuation coefficients of X-rays in different barite concrete used in radiation protection as shielding against ionizing radiation. Radiat. Phys. Chem. 140, 349–354. Kang, Y., 2010. Surface Scaling Mechanism and Prediction for Concrete. Doctoral dissertation. University of Michigan. Kobir Hossain, M.d., Rashid, M.A., Karim, M.d.R., 2015. Effect of cement content and size of coarse aggregate on the strength of brick aggregate concrete. DUET J 2, 20–24. Kolias, S., Georgiou, C., 2005. The effect of paste volume and of water content on the strength and water absorption of concrete. Cement Concr. Compos. 27, 211–216. Konigsberger, M., Pichler, B., Hellmich, C., 2014a. Micromechanics of ITZ-aggregate interaction in concrete Part I: stress concentration. J. Am. Ceram. Soc. 97, 535–542. K€ onigsberger, M., Pichler, B., Hellmich, C., 2014b. Micromechanics of ITZ-aggregate interaction in concrete Part II: strength upscaling. J. Am. Ceram. Soc. 97, 543–551. Li, Q., Deng, Z., Fu, H., 2004. Effect of aggregate type on mechanical behavior of dam concrete. ACI Mater. J. 101, 483–492. Meddah, M.S., Zitouni, S., Bel^ aabes, S., 2010. Effect of content and particle size distribution of coarse aggregate on the compressive strength of concrete. Constr. Build. Mater. 24, 505–512. Mesbahi, A., Azarpeyvand, A.A., Shirazi, A., 2011. Photo neutron production and backscattering in high density concretes used for radiation therapy shielding. Ann. Nucl. Energy 38, 2752–2756. Moavenzadeh, F., Kuguel, R., 1969. Fracture of concrete. J. Mater. 4, 497–519. Mohammed, T.U., Mahmood, A.H., 2016. Effects of maximum aggregate size on UPV of brick aggregate concrete. Ultrason 69, 129–136. Neville, A.M., 1996. Properties of Concrete. Addison Wesley Longman Limited Edinburgh Gate, Harlow Essex, England. Oto, B., Gür, A., Kavaz, E., Çakır, T., Yaltay, N., 2016. Determination of gamma and fast neutron shielding parameters of magnetite concretes. Prog. Nucl. Energy 92, 71–80. Oto, B., Yıldız, N., Korkut, T., Kavaz, E., 2015. Neutron shielding qualities and gamma ray buildup factors of concretes containing limonite ore. Nucl. Eng. Des. 293, 166–175. Ouda, A.S., 2015. Development of high-performance heavy density concrete using different aggregates for gamma-ray shielding. Prog. Nucl. Energy 79, 48–55. Piasta, W., Zarzycki, B., 2017. The effect of cement paste volume and w/c ratio on shrinkage strain, water absorption and compressive strength of high performance concrete. Constr. Build. Mater. 140, 395–402. Rezaei-Ochbelagh, D., Azimkhani, S., 2012. Investigation of gamma-ray shielding properties of concrete containing different percentages of lead. Appl. Radiat. Isot. 70, 2282–2286. Sagar Singh, B., Ramana, K.V., 2014. Mechanical properties of heavy weight concrete using heavy weight coarse- aggregate as hematite. Int. J. Res. Eng. Technol. 3, 264–269. Saidani, K., Ajam, L., Ouezdou, M.B., 2015. Barite powder as sand substitution in concrete: effect on some mechanical properties. Constr. Build. Mater. 95, 287–295. Salinas, I.C.P., Conti, C.C., Lopes, R.T., 2006. Effective density and mass attenuation coefficient for building material in Brazil. Appl. Radiat. Isot. 64 (1), 13–18. Saouma, V.E., Broz, J.J., Brühwiler, E., Boggs, H.L., 1991. Effect of aggregate and specimen size on fracture properties of dam concrete. J. Mater. Civ. Eng. 3, 204–218. Sharifi, S., Bagheri, R., Shirmardi, S.P., 2013. Comparison of shielding properties for ordinary, barite, serpentine and steel magnetite concretes using MCNP-4C code and available experimental results. Ann. Nucl. Energy 53, 529–534. Singh, V.P., Medhat, M.E., Badiger, N.M., Rahman, A.Z.M.S., 2015. Radiation shielding effectiveness of newly developed super conductors. Radiat. Phys. Chem. 106, 175–183.
Supplementary data to this article can be found online at https://doi. org/10.1016/j.pnucene.2019.103222. References Acevedo, C.E., Serrato, M.G., 2010. Determining the effects of radiation on aging concrete structures of nuclear reactors – 10243. In: Presented at WM2010 Conference. Phoenix, AZ (March). ACI 304.3R-96, 2001. Heavyweight Concrete Measuring, Mixing, Transporting and Placing, ACI Manual Concrete Practice. American Concrete Institute, Detroit. Ackay, B., Agar-Ozbek, A.S., Bayramov, F., Atahan, H.N., Sengul, C., Tasdemir, M.A., 2012. Interpretation of aggregate volume fraction effects on fracture behavior of concrete. Constr. Build. Mater. 28, 437–443. Aïtcin, P.C., 2011. High Performance Concrete. CRC Press. Akcaoglu, T., Tokyay, M., Celik, T., 2004. Effect of coarse aggregate size and matrix quality on ITZ and failure behavior of concrete under uniaxial compression. Cement Concr. Compos. 26, 633–638. Akkurt, I., Akyildirim, H., Mavi, B., Kilincarslan, S., Basyigit, C., 2010. Gamma-ray shielding properties of concrete including barite at different energies. Prog. Nucl. Energy 52 (7), 620–623. Akkurt, I., Basyigit, C., Akkas, A., Kılınçarslan, S., Mavi, B., Günoglu, K., 2012. Determination of some heavyweight aggregate half value layer thickness used for radiation shielding. Acta Phys. Pol. 121, 138–140. Akkurt, I., Canakci, H., 2011. Radiation attenuation of boron doped clay for 662, 1173 and 1332 keV gamma rays. Iran. J. Radiat. Res. 9 (1), 37–40. Akkurt, I., Mavi, B., Akkurt, A., Basyigit, C., Kilinsarslan, S., Yalim, H.A., 2005. Study on Z-dependence of partial and total mass attenuation coefficients. J. Quant. Spectrosc. Radiat. Transfer 94, 379–385. Al-Humaiqani, M.M., Shuraim, A.B., Hussain, R.R., 2013a. γ-radiation shielding properties of high strength high performance concretes prepared with different types of normal and heavy aggregates. Asian Trans. Eng. 3 (2), 18–28. Al-Humaiqani, M.M., Shuraim, A.B., Hussain, R.R., 2013b. Effect of compressive strength on γ-radiation attenuation coefficients for high performance concrete. IACSIT Int. J. Eng. Technol. 5 (5), 566–572. Al-khazraji, H., Benkemoun, N., Choinska, M., Khelidj, A., 2017. Meso-scale analysis of the aggregate size influence on the mechanical properties of heterogeneous materials using the Brazilian splitting test. Energy Procedia 139, 266–272. Alwaeli, M., 2017. Investigation of gamma radiation shielding and compressive strength properties of concrete containing scale and granulated lead-zinc slag wastes. J. Clean. Prod. 166, 157–162. Amparano, F.E., Xi, Y., Roh, Y.S., 2000. Experimental study on the effect of aggregate content on fracture behavior of concrete. Eng. Fract. Mech. 67, 65–84. Appa Rao, G., Raghu Prasad, B.K., 2011. Influence of interface properties on fracture behaviour of concrete. Indian Acad. Sci. 36, 193–208. Beygi, M.H.A., Kazemi, M.T., Vaseghi Amiri, J., Nikbin, I.M., Rabbanifar, S., Rahmani, E., 2014a. Evaluation of the effect of maximum aggregate size on fracture behavior of self compacting concrete. Constr. Build. Mater. 55, 202–211. Beygi, M.H.A., Kazemi, M.T., Nikbin, I.M., Vaseghi Amiri, J., Rabbanifar, S., Rahmani, E., 2014b. The influence of coarse aggregate size and volume on the fracture behavior and brittleness of self-compacting concrete. Cement Concr. Res. 66, 75–90. BS 8500-1, 2006. Method of Specifying and Guidance for the Specifier. Chen, B., Liu, J., 2004. Effect of aggregate on the fracture behaviour of high strength concrete. Constr. Build. Mater. 18, 585–590. Ç ullu, M., Bakırhan, E., 2018. Investigation of radiation absorption coefficients of leadzinc mine waste rock mixed heavy concrete at 662–1460 keV energy range. Constr. Build. Mater. 173, 17–27. Ç ullu, M., Ertas, H., 2016. Determination of the effect of lead mine waste aggregate on some concrete properties and radiation shielding. Constr. Build. Mater. 125, 625–631. Demir, F., Budak, G., Sahin, R., Karabulut, A., Oltulu, M., Serifoglu, K., Un, A., 2010. Radiation transmission of heavyweight and normal-weight concretes containing colemanite for 6MV and 18MV X-rays using linear accelerator. Ann. Nucl. Energy 37, 339–344. Demir, F., Budak, G., Sahin, R., Karabulut, A., Oltulu, M., Un, A., 2011. Determination of radiation attenuation coefficients of heavy weight and normal-weight concretes containing colemanite and barite for 0.663 MeV γ-rays. Ann. Nucl. Energy 38, 1274–1278. Elices, M., Rocco, C.G., 2008. Effect of aggregate size on the fracture and mechanical properties of a simple concrete. Eng. Fract. Mech. 75, 3839–3851. Elsharief, A., Cohen, M.D., Olek, J., 2003. Influence of aggregate size, water cement ratio and age on the microstructure of the interfacial transition zone. Cement Concr. Res. 33, 1837–1849. Esen, Y., Do� gan, Z.M., 2018. Investigation of usability of limonite aggregate in heavyweight concrete production. Prog. Nucl. Energy 105, 185–193. Esen, Y., Yilmazer, B., 2010. Investigation of some physical and mechanical properties of concrete produced with barite aggregate. Sci. Res. Essays 5, 3826–3833. Esen, Y., Yilmazer, B., 2011. An investigation of X-ray and radio isotope energy absorption of heavyweight concretes containing barite. Bull. Mater. Sci. 34, 169–175. Ezeldin, A.S., Aitcin, P.C., 1991. Effect of coarse aggregate on the behavior of normal and high-strength concretes. Cem. Concr. Aggregates 13, 121–124.
19
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222 Vishalakshi, K.P., Revathi, V., Sivamurthy Reddy, S., 2018. Effect of type of coarse aggregate on the strength properties and fracture energy of normal and high strength concrete. Eng. Fract. Mech. 194, 52–60. Vu, X.H., Daudeville, L., Malecot, Y., 2011. Effect of coarse aggregate size and cement paste volume on concrete behavior under high triaxial compression loading. Constr. Build. Mater. 25, 3941–3949. Wood, J., 2013. Computational Methods in Reactor Shielding. Elsevier. Wu, K., Chen, B., Yao, W., 2001. Study of the influence of aggregate size distribution on mechanical properties of concrete by acoustic emission technique. Cement Concr. Res. 31, 919–923. Xiao, J., Schneider, H., Donnecke, C., Konig, G., 2004. Wedge splitting test on fracture behaviour of ultra high strength concrete. Constr. Build. Mater. 18, 359–365. Yang, K.H., Mun, J.S., Lee, H., 2014. Workability and mechanical properties of heavyweight magnetite concrete. ACI Mater. J. 111, 273–282. Yılmaz, E., Baltas, H., Kırıs, E., Ustabas, I., Cevik, U., El-Khayatt, A.M., 2011. Gamma ray and neutron shielding properties of some concrete materials. Ann. Nucl. Energy 38, 2204–2212.
Singh, C., Singh, T., Kumar, A., Mudahar, G., 2004. Energy and chemical composition dependence of mass attenuation coefficients of building materials. Ann. Nucl. Energy 31, 1199–1205. Sliwinski, J., Tracz, T., 2013. Cement paste content as the factor influencing on compressive and splitting tensile strength of concrete. Cem. Lime Concr. 6, 353–361. Talaei, S., Jafari, M., Tarfan, S., 2014. The effect of ratio of aggregate to cement paste volume on structural lightweight concrete strength, viscosity, density and cost. Res. J. Environ. Earth Sci. 6 (9), 443–450. Tasdemir, C., Tasdemir, M.A., Lydon, F.D., Barr, B.I.G., 1996. Effects silica fume and aggregate size on the brittleness of concrete. Cement Concr. Res. 26, 63–68. Tijani, S.A., Kamal, S.M., Al-Hadeethi, Y., Arib, M., Hussein, M.A., Wageh, S., Dim, L.A., 2018. Radiation shielding properties of transparent erbium zinc tellurite glass system determined at medical diagnostic energies. J. Alloy. Comp. 741, 293–299. Tracz, T., Sliwinski, J., 2012. Effect of cement paste content and w/c ratio on concrete water absorption. Cem. Lime Concr. 3, 131–137. Uddin, M.T., Mahmood, A.H., Kamal, M.D.R.I., Yashin, S.M., Zihan, Z.U.A., 2017. Effects of maximum size of brick aggregate on properties of concrete. Constr. Build. Mater. 134, 713–726.
20
Contents lists available at ScienceDirect
Progress in Nuclear Energy journal homepage: http://www.elsevier.com/locate/pnucene
The influences of maximum aggregate size and cement content on the mechanical and radiation shielding characteristics of heavyweight concrete Omid. Lotfi-Omran a, Ali. Sadrmomtazi a, *, Iman.M. Nikbin b a b
Department of Civil Engineering, University of Guilan, Rasht, Iran Department of Civil Engineering, Rasht Branch, Islamic Azad University, Rasht, Iran
A R T I C L E I N F O
A B S T R A C T
Keywords: Heavyweight concrete Magnetite Radiation shielding Maximum aggregate size Cement content Protective properties
Nowadays, heavyweight concrete (HWC) is considered as one of the best materials for shielding against nuclear radiations due to its high density and good structural properties. On the other hand, cement content, aggregates and water to cement (w/c) ratio are the effective factors on the concrete behavior. Thus, in this investigation, the influences of cement content (c ¼ 350, 400 kg/m3), maximum aggregate size (MAS ¼ 12.5, 19, 25 mm) and w/c ratio (w/c ¼ 0.45, 0.65) on the shielding characteristics of heavyweight magnetite concrete against gamma-ray radiation were investigated. The protecting parameters which were assessed in this study are linear attenuation coefficient (LAC), mean free path (mfp), tenth value layer (TVL) and half value layer (HVL). The radiation sources of Cs137 and Co60 with photon energies of 0.662, 1.173 and 1.333 MeV were used. The results indicated that with the increase of MAS and decrease of cement content and w/c ratio, the passing flux will be reduced and shielding characteristics of heavyweight magnetite concrete will be improved.
1. Introduction Due to the wide utilization of nuclear technology for different pur poses in industry and medical uses, shielding against these hazardous radiations which have harmful environmental impacts seems necessary (Singh et al., 2004; Salinas et al., 2006; Akkurt et al., 2010). Because of appropriate structural properties, concrete is considered as one of the best materials for shielding against radiations. Particularly, with increasing concrete density using heavyweight aggregates, the thickness of protective members will be decreased and shielding characteristics of concrete will be enhanced considerably (Havranek, 1971; Neville, 1996; Acevedo and Serrato, 2010; Gencel et al., 2010, 2011; Demir et al., 2011; Yılmaz et al., 2011; Akkurt et al., 2012). According to ACI defi nition (ACI 304.3R, 2001), the density of heavyweight concrete (HWC) is more than 2600 kg/m3 and approximately the same relations for design of normal concrete can be used for it (BS 8500, 2006; Sagar Singh and Ramana, 2014). HWC is used in nuclear facilities for shielding against gamma or X-radiations or other places with the transmission possibility of radioactive radiations. The production of HWC is more expensive than normal concrete (Sagar Singh and Ramana, 2014). With the increase of concrete density, its mechanical properties will be altered
(Yang et al., 2014). Various investigations have been performed on the impact of heavyweight aggregates such as magnetite (Sharifi et al., 2013; Yang et al., 2014; Horszczaruk et al., 2015; Oto et al., 2016), hematite (Mesbahi et al., 2011), limonite (Oto et al., 2015; Esen and �an, 2018), lead-zinc (Rezaei-Ochbelagh and Azimkhani, 2012; Ç ullu Dog and Ertas, 2016; Alwaeli, 2017; Ç ullu and Bakırhan, 2018; Tijani et al., 2018), colemanite (Demir et al., 2010), barite (Esen and Yilmazer, 2010, 2011; Jankovic et al., 2016; Junior et al., 2017) and goethite (Ouda, 2015) on the attenuation of radioactive radiations. Generally, concrete is a three-phase material including cement paste, aggregates, and interfacial transition zone (ITZ) (Kang, 2010; Konigsberger et al., 2014a; €nigsberger et al., 2014b). Since aggregates occupy 70% of the con Ko crete volume, the mechanical properties of concrete are strongly dependent on them (Moavenzadeh and Kuguel, 1969; Feng et al., 1995; Amparano et al., 2000; Chen and Liu, 2004). In addition, various investigations have been performed on the in fluence of w/c ratio (Ince and Alyamac, 2008), size (Tasdemir et al., 1996; Amparano et al., 2000; Chen and Liu, 2004; Elices and Rocco, 2008; Grassl et al., 2010; Beygi et al., 2014a; Al-khazraji et al., 2017), type, shape, and texture (Xiao et al., 2004; Li et al., 2004; Appa Rao and Raghu Prasad, 2011; Hong et al., 2014; Vishalakshi et al., 2018), volume
* Corresponding author. E-mail addresses: [email protected] (Omid. Lotfi-Omran), [email protected], [email protected] (Ali. Sadrmomtazi), Nikbin@ iaurasht.ac.ir, [email protected] (Iman.M. Nikbin). https://doi.org/10.1016/j.pnucene.2019.103222 Received 29 July 2019; Received in revised form 21 October 2019; Accepted 20 December 2019 Available online 13 January 2020 0149-1970/© 2019 Elsevier Ltd. All rights reserved.
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Table 1 The mix designs concrete samples utilized in the present research. MAS (mm)
w/c
c (kg/m3)
Mix.ID
Sand (kg/m3)
4.75–12.5 (mm)
4.75–19 (mm)
4.75–25 (mm)
12.5
0.45
350 400 350 400
D12.5W0.45C350 D12.5W0.45C400 D12.5W0.65C350 D12.5W0.65C400
1825.3 1726.5 1664 1542.3
1444 1366 1316.5 1220.1
– – – –
– – – –
3783.9 3680.6 3558 3422.4
350 400 350 400
D19W0.45C350 D19W0.45C400 D19W0.65C350 D19W0.65C400
1829.4 1730.4 1667.8 1545.7
– – – –
1447.3 1369 1319.4 1223
– – – –
3791.2 3687.5 3564 3428.7
350 400 350 400
D25W0.45C350 D25W0.45C400 D25W0.65C350 D25W0.65C400
1850.5 1750.4 1687 1563.5
– – – –
– – – –
1464 1384.4 1334.6 1237
3829.1 3723.3 3599.2 3460.5
0.65
19
0.45 0.65
25
0.45 0.65
Coarse Aggregate (kg/m3)
fraction of aggregates (Beygi et al., 2014b; Ackay et al., 2012), aggregate size distribution (Wu et al., 2001) and ITZ (Guinea et al., 2002; €nigsberger et al., 2014b) on the me Konigsberger et al., 2014a; Ko chanical and fracture characteristics of concretes. Uddin et al. (2017) found that for low cement content, concrete compressive strength in creases with increasing maximum aggregate size (MAS). Aïtcin (2011) showed that ITZ quality drops with increasing MAS which leads to the reduction of mechanical characteristics of concrete. However, Vu et al. (2011) reported improvement of concrete compressive strength with increasing MAS. Meddah et al. (2010) and Kobir Hossain et al. (2015) depicted that with increasing MAS, compressive strength of concrete increases. Ezeldin and Aitcin (1991) stated that aggregate size does not affect concrete behavior. There are different investigations on the application of heavyweight aggregates in concrete. Esen and Do� gan (2018) showed that increase of heavyweight limonite aggregates results in the reduction of tensile, flexural and compressive strengths and radiation permeability of con crete and increase of its water absorption. Ç ullu and Bakırhan (2018) showed that strength grade of concrete affects the coefficient of radia tion absorption in heavyweight lead-zinc concretes. The results of studies indicated that application of barite powder (Saidani et al., 2015) and barite aggregates (Gonzalez-Ortega et al., 2015) in heavyweight concrete for the purpose of shielding against ultraviolet (UV) radiations in nuclear facilities and hospitals resulted in the decrease of concrete mechanical properties. However, heavyweight magnetite concrete showed better mechanical properties and radiation attenuation power than heavyweight concretes made by barite and goethite (Ouda, 2015). Jankovic et al. (2016) found that utilization of barite aggregates leads to the decrease of compressive strength and increase of flexural strength. Oto et al. (2016) concluded that the performance of heavyweight magnetite concrete in attenuation of gamma and neutron rays has been acceptable. In addition, Al-Humaiqani et al. (2013a) and Al-Humaiqani et al. (2013b) depicted that linear relationship exists between gamma-ray attenuation and compressive strength in high performance concrete (HPC). The influences of w/c ratio and cement paste volume on the ordinary concrete have been investigated previously (Kolias and Georgiou, 2005;
Unit Weight (kg/m3)
Elsharief et al., 2003). Tracz and Sliwinski (2012) and Sliwinski and Tracz (2013) found that with increasing cement paste volume, water absorption and compressive strength of concrete increases and de creases, respectively. Similar results were reported for lightweight concrete (Talaei et al., 2014). Regarding literature, the effects of MAS, w/c ratio and cement con tent on the mechanical properties of different types of concretes have been assessed in previous studies. In this research, due to the lack of comprehensive investigations, it has been attempted to explore the in fluences of MAS, w/c ratio and cement content on the mechanical characteristics (compressive strength, tensile strength, modulus of elasticity) and also shielding parameters (linear attenuation coefficient, mean free path, tenth value layer and half value layer) of heavyweight magnetite concrete. 2. Experimental program 2.1. Materials In this investigation, magnetite aggregates from Chadormalu mines located in the Yazd Province of Iran were employed for preparation of the HWC specimens. For magnetite gravel, three different maximum aggregate sizes (MAS) of 12.5, 19 and 25 mm with specific gravity of 4.39, 4.41 and 4.43, respectively, were provided. Moreover, magnetite sand with a fineness modulus of 3.3 and type II Neka Portland cement were utilized. In order to prevent the impact of water absorption of aggregates during mixing procedure and to evaluate the real influence of aggregates on the concrete characteristics, the aggregates were utilized in a saturated surface dry condition. In all mixes, a polycarboxylatebased superplasticizer was used for appropriate workability properties. 2.2. Mixture design Totally, 12 mixing designs including three maximum aggregate sizes (MAS ¼ 12.5, 19 and 25 mm), two cement contents (c ¼ 350 and 400 kg/ m3) and two water to cement ratios (w/c ¼ 0.45 and 0.65) were considered in this research (Table 1).
2
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 1. (a): Test process (b): schematic view of experimental set up for measurement of radiation attenuation.
3
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 2. A linear fit for determination of the LAC values (for mix D25W0.45C350 at different energy levels).
4
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 3. Variation of fc with MAS, cement content and w/c ratio.
Table 2 The obtained mechanical properties for various MAS, cement contents and w/c ratios. Mix.ID
MAS (mm)
w/c
c (kg/m3)
fc (MPa)
E (GPa)
ft (MPa)
Density (kg/m3)
D12.5W0.45C350 D12.5W0.45C400 D12.5W0.65C350 D12.5W0.65C400
12.5
0.45
350 400 350 400
55.9 63.3 31.8 36.6
36.1 36.6 29.6 32.7
4.75 5.06 3.5 4.1
3783.9 3680.6 3558 3422.4
D19W0.45C350 D19W0.45C400 D19W0.65C350 D19W0.65C400
19
350 400 350 400
57.5 62.8 31.2 35.2
36.33 36.17 29.3 32.4
4.65 4.91 3.1 3.6
3791.2 3687.5 3564 3428.7
D25W0.45C350 D25W0.45C400 D25W0.65C350 D25W0.65C400
25
350 400 350 400
60.1 62.4 31.15 32.7
36.6 36.04 29.18 31.9
4.43 4.87 3 3.6
3829.1 3723.3 3599.2 3460.5
0.65
0.45 0.65
0.45 0.65
2.3. Specimens preparation and test methods
test, respectively. Using Beer-Lambert’s law, the parameter LAC (linear attenuation coefficient) can be determined (Wood, 2013):
2.3.1. Mechanical properties For each experimental series of tests, four cubes with dimensions of 10 � 10 � 10 cm were prepared to obtain the compressive strength (fc) based on BS EN 12390 (2000) and six standard cylinders with di mensions of 15 � 30 cm were tested to achieve splitting tensile strength (ft) and modulus of elasticity (E) and based on ASTM C496 (2017) and ASTM C469 (2014), respectively. The prepared samples were cured under water with the temperature of approximately 20 � C for 28 days.
1 D0 LAC ¼ ln t D
(1)
In Eq. (1), D0 and D are the background subtracted number of counts recorded in detector without and with an absorbent material between detector and source, respectively, and t is the thickness of material. As observed in Fig. 2, LAC is the slope of the straight line obtaining by drawing variation of each ln (D0/D) with thickness (t). TVL (tenth value layer) and HVL (half value layer) are used for determination of radiation shielding effectiveness. TVL and HVL are defined as the thicknesses of an absorber that can decrease the radiation of gamma to tenth and to half of its intensity, respectively (Akkurt and Canakci, 2011):
2.3.2. Gamma-ray attenuation test For gamma ray attenuation test, a 3 ʺ � 3 ʺ sodium iodide scintilla tion NaI (T1) detector with a multi-channel analyzer was employed in this investigation. The radiation sources of Cs137 and Co60 with energies of 0.662, 1.173 and 1.333 MeV were used. The 30 � 30 � 6 cm concrete specimens with various thicknesses (t) of 6–24 cm were placed in front of a collimated beam emerged from radiation sources. Fig. 1(a) and (b) illustrate process and schematic arrangement of concrete samples in the
5
TVL ¼ ln 10=LAC
(2)
HVL ¼ ln 2=LAC
(3)
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 4. Variation of ITZ with MAS.
Fig. 5. Relation between fc, cement content and MAS.
6
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 6. Variation of ft with MAS, cement content and w/c ratio.
Fig. 7. Variation of E with MAS, w/c ratio and cement content.
7
6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24
D12.5W0.45C350
8
D25W0.65C400
D25W0.65C350
D25W0.45C400
D25W0.45C350
D19W0.65C400
D19W0.65C350
D19W0.45C400
D19W0.45C350
D12.5W0.65C400
D12.5W0.65C350
D12.5W0.45C400
t (cm)
Mix.ID 705322 � 1323 137361 � 802 27811 � 151 5148 � 89 701289 � 3666 158444 � 12 30130 � 960 6683 � 440 705311 � 1250 159810 � 416 31001 � 622 7010 � 80 729932 � 3232 171108 � 210 35218 � 870 16520 � 342 655434 � 3407 123599 � 583 22847 � 343 4813 � 94 693216 � 2544 154318 � 899 29731 � 464 5456 � 777 700315 � 1475 154683 � 691 29751 � 68 6196 � 150 725329 � 1530 170931 � 560 34622 � 177 13402 � 85 623101 � 2587 127410 � 713 19853 � 275 2741 � 150 651255 � 2006 133791 � 708 25010 � 459 4298 � 181 706517 � 233 140129 � 968 28001 � 72 5298 � 545 715140 � 2451 162399 � 982 33413 � 312 8731 � 17
D
Ln(D0/D) 0.10 1.74 3.34 5.02 0.11 1.60 3.26 4.76 0.10 1.59 3.23 4.72 0.07 1.52 3.10 3.86 0.18 1.85 3.53 5.09 0.12 1.62 3.27 4.97 0.11 1.62 3.27 4.84 0.08 1.52 3.12 4.07 0.23 1.81 3.67 5.66 0.18 1.77 3.44 5.20 0.10 1.72 3.33 4.99 0.09 1.57 3.15 4.50
Table 3 The obtained radiation test results for different MAS, cement contents and w/c ratios (Cs137 -662 keV source).
0.201
0.220
0.227
0.246
0.182
0.214
0.218
0.225
0.179
0.209
0.211
0.221
LAC (cm
1
)
HVL (cm)
3.44
3.15
3.05
2.81
3.80
3.23
3.18
3.08
3.87
3.31
3.28
3.13
TVL (cm)
11.45
10.46
10.14
9.36
12.65
10.75
10.56
10.23
12.86
11.01
10.91
10.41
mfp (cm)
4.97
4.54
4.40
4.06
5.50
4.67
4.58
4.44
5.58
4.78
4.74
4.52
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24
D12.5W0.45C350
9
D25W0.65C400
D25W0.65C350
D25W0.45C400
D25W0.45C350
D19W0.65C400
D19W0.65C350
D19W0.45C400
D19W0.45C350
D12.5W0.65C400
D12.5W0.65C350
D12.5W0.45C400
t (cm)
Mix.ID 42530 � 522 12246 � 3 3597 � 751 1050 � 2 45289 � 135 4571 � 111 4347 � 658 1562 � 4 46113 � 410 15261 � 97 5274 � 209 2098 � 44 46815 � 161 15731 � 52 5412 � 455 2434 � 749 42201 � 318 11942 � 45 3388 � 171 873 � 180 45240 � 261 14620 � 413 4363 � 242 1456 � 81 45720 � 858 14584 � 309 5074 � 230 1920 � 11 45902 � 66 14691 � 87 5205 � 45 2019 � 540 39932 � 112 1052 � 74 2897 � 560 419 � 22 43818 � 797 12853 � 325 3702 � 668 1314 � 7 43467 � 411 14123 � 569 4368 � 82 1636 � 12 45600 � 230 14167 � 188 4675 � 181 1709 � 16
D
Ln(D0/D) 0.95 2.19 3.42 4.65 0.89 2.00 3.23 4.25 0.87 1.97 3.04 3.96 0.85 1.94 3.01 3.81 0.95 2.22 3.48 4.83 0.89 2.02 3.22 4.32 0.87 2.02 3.07 4.04 0.87 2.01 3.05 4.00 1.01 2.35 3.63 5.56 0.92 2.14 3.39 4.42 0.93 2.05 3.22 4.20 0.88 2.05 3.15 4.16
Table 4 The obtained radiation test results for different MAS, cement contents and w/c ratios (Co60 -1173 keV source).
0.176
0.178
0.188
0.229
0.169
0.171
0.182
0.203
0.163
0.168
0.180
0.196
LAC (cm
)
1
HVL (cm)
3.93
3.90
3.68
3.02
4.10
4.05
3.80
3.41
4.25
4.12
3.85
3.53
TVL (cm)
13.08
12.93
12.24
10.05
13.62
13.46
12.65
11.34
14.12
13.70
12.80
11.74
mfp (cm)
5.68
5.61
5.32
4.36
5.91
5.84
5.50
4.92
6.13
5.95
5.55
5.10
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24 6 12 18 24
D12.5W0.45C350
10
D25W0.65C400
D25W0.65C350
D25W0.45C400
D25W0.45C350
D19W0.65C400
D19W0.65C350
D19W0.45C400
D19W0.45C350
D12.5W0.65C400
D12.5W0.65C350
D12.5W0.45C400
t (cm)
Mix.ID 55081 � 684 16799 � 218 4847 � 264 1046 � 279 57063 � 535 18944 � 308 5981 � 112 1940 � 201 58813 � 144 20466 � 499 7645 � 315 2470 � 223 58812 � 684 19730 � 218 7682 � 264 2911 � 279 54018 � 409 16259 � 64 4391 � 623 1080 � 24 57091 � 104 18840 � 836 5964 � 47 1798 � 42 58779 � 144 21722 � 499 7044 � 315 2314 � 223 58815 � 409 19938 � 64 7351 � 623 2587 � 24 52801 � 409 15576 � 64 4028 � 623 749 � 24 55320 � 731 17259 � 177 4978 � 283 1604 � 346 57222 � 228 19630 � 224 6022 � 316 2002 � 122 57401 � 535 20664 � 308 6601 � 112 2181 � 201
D
Ln(D0/D) 0.86 2.04 3.29 4.82 0.82 1.92 3.08 4.20 0.79 1.85 2.83 3.96 0.79 1.88 2.83 3.80 0.88 2.08 3.39 4.79 0.82 1.93 3.08 4.28 0.79 1.79 2.91 4.03 0.79 1.87 2.87 3.92 0.90 2.12 3.47 5.15 0.85 2.02 3.26 4.39 0.82 1.89 3.07 4.17 0.81 1.84 2.98 4.09
Table 5 The obtained radiation test results for different MAS, cement contents and w/c ratios (Co60 -1333 keV source).
0.172
0.176
0.186
0.214
0.165
0.169
0.180
0.201
0.160
0.166
0.177
0.201
LAC (cm
)
1
4.02
3.93
3.72
3.24
4.20
4.10
3.85
3.44
4.33
4.17
3.91
3.44
HVL (cm)
13.87
13.08
12.38
10.76
13.95
13.62
12.80
11.45
14.40
13.87
13.00
11.45
TVL (cm)
5.81
5.68
5.37
4.67
6.00
5.91
5.55
4.97
6.25
6.02
5.65
4.97
mfp (cm)
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 8. Variation of LAC with MAS, cement content and w/c ratio (for Cs137 and Co60 radioactive sources).
11
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 9. Relation between LAC and density (for different MAS, cement contents and w/c ratios).
The parameter mfp (mean free path) is the average distance between two successive interactions of photons and calculated as: mfp ¼ 1=LAC
w/c ratio, size of aggregate and cement to aggregate ratio. Since these factors are not independent from each other, the role of aggregates is not very obvious (Elices and Rocco, 2008). Meddah et al. (2010) showed that concrete compressive strength improves with increasing MAS. Wu et al. (2001) concluded that concrete compressive strength rises with increasing MAS up to 15 mm and reduces beyond this size. Fig. 5 shows variation of fc with MAS and the comparison of the results found in this investigation with the results of previous investigations.
(4)
3. Results and discussions 3.1. Compressive strength Fig. 3 and Table 2 depict the effects of MAS, cement content and w/c ratio on the compressive strength (fc). It can be observed that for low cement content and w/c ratio values (c ¼ 350 kg/m3 and w/c ¼ 0.45), compressive strength increases with increasing MAS from 12.5 to 25 mm. It can be related to two reasons: 1- For low cement content (c ¼ 350 kg/m3), the role of aggregates will be more considerable and the bridging effect in the cement matrix will be improved. Thus, more energy is required for fracture of concrete specimens. 2-According to Fig. 4, the perimeter of ITZ decreases with increasing MAS (Mohammed and Mahmood, 2016; Uddin et al., 2017). Hence, at the cement content of 350 kg/m3, ITZ quality will be enhanced and the possibility of internal bleeding will be reduced with the increase of MAS. However, with the increase of MAS for high cement content (c ¼ 400 kg/m3), the excess amount of cement paste leads to the separation be tween aggregates, increase of the internal bleeding possibility and reduction of compressive strength. Piasta and Zarzycki (2017) found that for HPC, compressive strength and water absorption decrease with the increase of w/c ratio and volume of cement paste. Kolias and Georgiou (2005) concluded that concrete strength is dependent on ITZ,
3.2. Tensile strength and modulus of elasticity Fig. 6 and Table 2 illustrate variation of the tensile strength (ft) of heavyweight magnetite concrete with MAS, cement content and w/c ratio. It can be observed that with increasing MAS, tensile strength re duces which this issue is more considerable for higher w/c ratio (w/c ¼ 0.65). Elsharief et al. (2003) stated that with the increase of MAS, more water will be present in the cement paste. Thus, the porosity increases and ITZ quality drops and since tensile strength is strongly dependent on ITZ, this strength decreases. Some other researchers also reported reduction of ft with the increase of MAS (Saouma et al., 1991; Tasdemir et al., 1996; Akcaoglu et al., 2004). Fig. 7 and Table 2 illustrate the influences of MAS, cement content and w/c ratio on the modulus of elasticity (E) which is similar to Fig. 3. Tasdemir et al. (1996) and Uddin et al. (2017) also found similar results. 3.3. Gamma-ray radiation shielding Tables 3–5 present the measured protecting parameters (LAC, HVL, TVL, mfp) of heavyweight magnetite concrete containing different MAS, 12
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 10. Variation of LAC with density (for Co60 and Cs137 radioactive sources).
13
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 11. Variation of the LAC with fc (for Co60 and Cs137 radioactive sources).
14
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 12. Gamma-ray energy spectrum of heavyweight magnetite concrete with different MAS and without an absorbent material (background).
cement contents and w/c ratios. According to Tables 3–5 and Fig. 8, it is obvious that LAC improves with the increase of MAS and reduction of cement content and w/c ratio. With increasing MAS, the possibility of radiation interaction with concrete increases and consequently LAC rises. It can be observed that at c ¼ 400 kg/m3 and w/c ¼ 0.65, LAC improves 12.3, 7.9 and 7.5% with increasing MAS from 12.5 to 25 mm for energies of 0.662, 1.173 and 1.333 MeV, respectively. By reducing cement content and w/c ratio, LAC increases too. For example, at Cs137 -0.662 MeV, the LAC of the mix D12.5W0.45C350 is 23.5% greater than LAC of the mix D12.5W0.65C400. In addition, for the same level of energy (Cs137 -0.662 MeV), the LAC of the mix D25W0.45C350 is 37.4% greater than LAC of the mix D12.5W0.65C400 that indicates the com bined influences of MAS, w/c ratio and cement content on the LAC. In addition, it can be observed that with increasing energy level from 0.662 to 1.333 MeV, concrete samples can absorb less radiation and LAC will be reduced. In order to compensate this effect, the shielding con crete thickness should be increased. The variation of LAC with photon energy is due to the variation of absorption mechanism and interaction of photon with shielding material. For energy levels of low, medium and high (more than 1.022 MeV), the interaction mechanism is mainly photoelectric phenomenon, Compton scattering and pair production, respectively (Akkurt et al., 2005). Since the mixture calculation of the specimens was conducted considering volume, density of heavyweight magnetite concrete in creases with increasing MAS from 12.5 to 25 mm. With the reduction of cement content, the role of heavyweight magnetite aggregates becomes more considerable which leads to the higher growth of density (Fig. 9). It is worth remarking that porosity of cement paste and ITZ decreases with reducing w/c ratio. This issue results in the increase of density and enhancement of concrete microstructure. Therefore, passing flux de creases and LAC increases. Singh et al. (2015) and Junior et al. (2017) found similar results. Fig. 10 shows the relations between LAC and density using linear
regression and the comparison of the results with other previous in vestigations. It is obvious that for all three energy levels, LAC increases with increasing density. As observed in Fig. 11, for c ¼ 350 kg/m3 and w/c ¼ 0.45, LAC and compressive strength increase with increasing MAS from 12.5 to 25 mm. It can be related to the fact that at low w/c ratio, the microstructure of cement paste and ITZ improve that leads to the improvement of LAC and fc. With increasing cement content in volume mix design, the role of aggregates in concrete becomes less which results in the decrease of density and LAC. 3.4. Energy spectrums It is obvious in Fig. 12 that for c ¼ 350 kg/m3 and w/c ¼ 0.45, passing flux decreases in presence of the heavyweight magnetite con crete and this reduction becomes more considerable with increasing MAS (for all three levels of energy). As mentioned previously, LAC re duces with increasing energy. Thus, the photon absorption values of samples for 0.662 MeV have been more than other two energy levels. 3.5. Effect of thickness Fig. 13 depicts variation of LAC with thickness (t) of heavyweight magnetite concrete samples at 0.662, 1.173 and 1.333 MeV energy levels. It can be concluded that due to the higher interaction of gamma radiations with concrete, LAC increases with increasing concrete thickness which this effect is more remarkable for Cs137 source. 3.6. mfp As observed in Fig. 14, mfp decreases with the reduction of w/c ratio and cement content and increase of MAS. It can be concluded that by performing variations in the constituents of heavyweight magnetite concrete, energy can be attenuated in less distance and thus, less
15
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 13. Variation of LAC with thickness of heavyweight magnetite concrete specimens (for Co60 and Cs137 sources).
16
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 14. Variation of mfp with the photon energy for different MAS, cement contents and w/c ratios.
concrete thickness will be required. Moreover, it is clear that less dis tance is needed for attenuation of lower energy level (0.662 MeV). However, for higher energy level (1.333 MeV), more distance is required for energy attenuation.
1 At low cement content, the compressive strength and modulus of elasticity of heavyweight magnetite aggregate improve with the in crease of MAS. However, a decreasing trend was observed for high cement content. With the increase of MAS, ITZ quality drops. Since value of concrete tensile strength strongly depends on ITZ, this value decreases with increasing MAS. This trend was seen for all cement contents and w/c ratios. 2 With the increase of MAS and the reduction of w/c ratio and cement content, LAC increased. For c ¼ 400 kg/m3 and w/c ¼ 0.65, LAC increases 12% with increasing MAS from 12.5 to 25 mm and for c ¼ 350 kg/m3 and w/c ¼ 0.45, LAC improves 22% with increasing MAS from 12.5 to 25 mm (at the energy level of 0.662 MeV). 3 For all three levels of energy, with the increase of MAS and the reduction of w/c ratio and cement content, concrete density and LAC increase. In addition, with the increase of energy level from 0.662 to 1.333 MeV, the passing flux increases and LAC decreases. In order to compensate this effect, the thickness of the shielding concrete should be increased. For a constant cement content and w/c ratio, the passing flux decreases with increasing MAS from 12.5 to 25 mm for all three levels of energy. 4 The transmission rate decreases with increasing MAS and decreasing cement content and w/c ratio. Thus, HVL and TVL values will be reduced. For instance, for D25W0.45C350, HVL and TVL values are 25, 28 and 27% lower than D12.5W0.65C400 HVL and TVL ones for Co60 -1333, Co60 -1173 and Cs137 -662 keV, respectively.
3.7. HVL and TVL The transmission rate of gamma-ray is one of the effective factors that can specify the required thickness of an absorbent material to stop gamma-ray. From this viewpoint, HVL and TVL are two protecting pa rameters which show absorber thickness that decrease the transmission rate of gamma-ray to half and tenth, respectively. As observed in Fig. 15, the transmission rate reduces with the increase of MAS and the decrease of w/c ratio and cement content that consequently leads to the reduction of HVL and TVL. For instance, for D25W0.45C350, HVL and TVL values are 25, 28 and 27% lower than D12.5W0.65C400 ones for Co60 -1333, Co60 -1173 and Cs137 -662 keV, respectively. With increasing MAS of heavyweight magnetite aggregates and reducing cement content, the concrete density improves. In addition, with decreasing w/c ratio, the quality of ITZ and cement paste will be enhanced which increases pos sibility of gamma-ray interaction with concrete and reduces the required concrete thickness for radiation attenuation. This issue can be applied for places where there is not enough space for construction of shielding concrete wall.
Finally, it can be concluded that for places with limit of enough space for construction of shielding concrete, the thickness of heavyweight magnetite concrete can be reduced by increasing MAS and decreasing w/c ratio and cement content.
4. Conclusions Since aggregates, cement content and w/c ratio are known as the principal factors influencing concrete behavior, the impacts of these factors on the mechanical and shielding characteristics of heavyweight magnetite concrete have been explored in this experimental research. The following results can be drawn based on the present study:
17
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Fig. 15. Variation of transmission rate with thickness (for Co60 and Cs137 sources).
18
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222
Appendix A. Supplementary data
Feng, N.Q., Ji, X.H., Zhuang, Q.F., Ding, J.T., 1995. Effect of concrete materials on fracture performance. In: Wittmann, F.H. (Ed.), Fracture Mechanics of Concrete Structures, Proc. Of FRAMCOS-2.D-79104 Freiburg. Aedificatio Publishers, pp. 119–124. Gencel, O., Bozkurt, A., Kam, E., Korkut, T., 2011. Determination and calculation of gamma and neutron shielding characteristics of concretes containing different hematite proportions. Ann. Nucl. Energy 38, 2719–2723. Gencel, O., Brostow, W., Ozel, C., Filiz, M., 2010. An investigation on the concrete properties containing colemanite. Int. J. Phys. Sci. 5, 216–225. Gonzalez-Ortega, M.A., Cavalaro, S.H.P., Aguado, A., 2015. Influence of barite aggregate friability on mixing process and mechanical properties of concrete. Constr. Build. Mater. 74, 169–175. Grassl, P., Wong, H.S., Buenfeld, N.R., 2010. Influence of aggregate size and volume fraction on shrinkage induced micro-cracking of concrete and mortar. Cement Concr. Res. 40, 85–93. Guinea, G.V., El-Sayed, K., Rocco, C.G., Elices, M., Planas, J., 2002. The effect of the bond between the matrix and the aggregates on the cracking mechanism and fracture parameters of concrete. Cement Concr. Res. 32, 1961–1970. Havranek, M., 1971. The calculation of the total dose in concretes for radiation shielding design. Nucl. Eng. Des. 16, 249–252. Hong, L., Gu, X., Lin, F., 2014. Influence of aggregate surface roughness on mechanical properties of interface and concrete. Constr. Build. Mater. 65, 338–349. Horszczaruk, E., Sikora, P., Zaporowski, P., 2015. Mechanical properties of shielding concrete with magnetite aggregate subjected to high temperature. Procedia Eng 108, 39–46. Ince, R., Alyamac, K.E., 2008. Determination of fracture parameters of concrete based on the water-cement ratio. Indian J. Eng. Mater. Sci. 15, 14–22. Jankovic, K., Stankovic, S., Bojovic, D., Stojanovic, M., Antic, L., 2016. The influence of nano-silica and barite aggregate on properties of ultra high performance concrete. Constr. Build. Mater. 126, 147–156. Junior, T.A.A., Nogueira, M.S., Vivolo, V., Potiens, M.P.A., Campos, L.L., 2017. Mass attenuation coefficients of X-rays in different barite concrete used in radiation protection as shielding against ionizing radiation. Radiat. Phys. Chem. 140, 349–354. Kang, Y., 2010. Surface Scaling Mechanism and Prediction for Concrete. Doctoral dissertation. University of Michigan. Kobir Hossain, M.d., Rashid, M.A., Karim, M.d.R., 2015. Effect of cement content and size of coarse aggregate on the strength of brick aggregate concrete. DUET J 2, 20–24. Kolias, S., Georgiou, C., 2005. The effect of paste volume and of water content on the strength and water absorption of concrete. Cement Concr. Compos. 27, 211–216. Konigsberger, M., Pichler, B., Hellmich, C., 2014a. Micromechanics of ITZ-aggregate interaction in concrete Part I: stress concentration. J. Am. Ceram. Soc. 97, 535–542. K€ onigsberger, M., Pichler, B., Hellmich, C., 2014b. Micromechanics of ITZ-aggregate interaction in concrete Part II: strength upscaling. J. Am. Ceram. Soc. 97, 543–551. Li, Q., Deng, Z., Fu, H., 2004. Effect of aggregate type on mechanical behavior of dam concrete. ACI Mater. J. 101, 483–492. Meddah, M.S., Zitouni, S., Bel^ aabes, S., 2010. Effect of content and particle size distribution of coarse aggregate on the compressive strength of concrete. Constr. Build. Mater. 24, 505–512. Mesbahi, A., Azarpeyvand, A.A., Shirazi, A., 2011. Photo neutron production and backscattering in high density concretes used for radiation therapy shielding. Ann. Nucl. Energy 38, 2752–2756. Moavenzadeh, F., Kuguel, R., 1969. Fracture of concrete. J. Mater. 4, 497–519. Mohammed, T.U., Mahmood, A.H., 2016. Effects of maximum aggregate size on UPV of brick aggregate concrete. Ultrason 69, 129–136. Neville, A.M., 1996. Properties of Concrete. Addison Wesley Longman Limited Edinburgh Gate, Harlow Essex, England. Oto, B., Gür, A., Kavaz, E., Çakır, T., Yaltay, N., 2016. Determination of gamma and fast neutron shielding parameters of magnetite concretes. Prog. Nucl. Energy 92, 71–80. Oto, B., Yıldız, N., Korkut, T., Kavaz, E., 2015. Neutron shielding qualities and gamma ray buildup factors of concretes containing limonite ore. Nucl. Eng. Des. 293, 166–175. Ouda, A.S., 2015. Development of high-performance heavy density concrete using different aggregates for gamma-ray shielding. Prog. Nucl. Energy 79, 48–55. Piasta, W., Zarzycki, B., 2017. The effect of cement paste volume and w/c ratio on shrinkage strain, water absorption and compressive strength of high performance concrete. Constr. Build. Mater. 140, 395–402. Rezaei-Ochbelagh, D., Azimkhani, S., 2012. Investigation of gamma-ray shielding properties of concrete containing different percentages of lead. Appl. Radiat. Isot. 70, 2282–2286. Sagar Singh, B., Ramana, K.V., 2014. Mechanical properties of heavy weight concrete using heavy weight coarse- aggregate as hematite. Int. J. Res. Eng. Technol. 3, 264–269. Saidani, K., Ajam, L., Ouezdou, M.B., 2015. Barite powder as sand substitution in concrete: effect on some mechanical properties. Constr. Build. Mater. 95, 287–295. Salinas, I.C.P., Conti, C.C., Lopes, R.T., 2006. Effective density and mass attenuation coefficient for building material in Brazil. Appl. Radiat. Isot. 64 (1), 13–18. Saouma, V.E., Broz, J.J., Brühwiler, E., Boggs, H.L., 1991. Effect of aggregate and specimen size on fracture properties of dam concrete. J. Mater. Civ. Eng. 3, 204–218. Sharifi, S., Bagheri, R., Shirmardi, S.P., 2013. Comparison of shielding properties for ordinary, barite, serpentine and steel magnetite concretes using MCNP-4C code and available experimental results. Ann. Nucl. Energy 53, 529–534. Singh, V.P., Medhat, M.E., Badiger, N.M., Rahman, A.Z.M.S., 2015. Radiation shielding effectiveness of newly developed super conductors. Radiat. Phys. Chem. 106, 175–183.
Supplementary data to this article can be found online at https://doi. org/10.1016/j.pnucene.2019.103222. References Acevedo, C.E., Serrato, M.G., 2010. Determining the effects of radiation on aging concrete structures of nuclear reactors – 10243. In: Presented at WM2010 Conference. Phoenix, AZ (March). ACI 304.3R-96, 2001. Heavyweight Concrete Measuring, Mixing, Transporting and Placing, ACI Manual Concrete Practice. American Concrete Institute, Detroit. Ackay, B., Agar-Ozbek, A.S., Bayramov, F., Atahan, H.N., Sengul, C., Tasdemir, M.A., 2012. Interpretation of aggregate volume fraction effects on fracture behavior of concrete. Constr. Build. Mater. 28, 437–443. Aïtcin, P.C., 2011. High Performance Concrete. CRC Press. Akcaoglu, T., Tokyay, M., Celik, T., 2004. Effect of coarse aggregate size and matrix quality on ITZ and failure behavior of concrete under uniaxial compression. Cement Concr. Compos. 26, 633–638. Akkurt, I., Akyildirim, H., Mavi, B., Kilincarslan, S., Basyigit, C., 2010. Gamma-ray shielding properties of concrete including barite at different energies. Prog. Nucl. Energy 52 (7), 620–623. Akkurt, I., Basyigit, C., Akkas, A., Kılınçarslan, S., Mavi, B., Günoglu, K., 2012. Determination of some heavyweight aggregate half value layer thickness used for radiation shielding. Acta Phys. Pol. 121, 138–140. Akkurt, I., Canakci, H., 2011. Radiation attenuation of boron doped clay for 662, 1173 and 1332 keV gamma rays. Iran. J. Radiat. Res. 9 (1), 37–40. Akkurt, I., Mavi, B., Akkurt, A., Basyigit, C., Kilinsarslan, S., Yalim, H.A., 2005. Study on Z-dependence of partial and total mass attenuation coefficients. J. Quant. Spectrosc. Radiat. Transfer 94, 379–385. Al-Humaiqani, M.M., Shuraim, A.B., Hussain, R.R., 2013a. γ-radiation shielding properties of high strength high performance concretes prepared with different types of normal and heavy aggregates. Asian Trans. Eng. 3 (2), 18–28. Al-Humaiqani, M.M., Shuraim, A.B., Hussain, R.R., 2013b. Effect of compressive strength on γ-radiation attenuation coefficients for high performance concrete. IACSIT Int. J. Eng. Technol. 5 (5), 566–572. Al-khazraji, H., Benkemoun, N., Choinska, M., Khelidj, A., 2017. Meso-scale analysis of the aggregate size influence on the mechanical properties of heterogeneous materials using the Brazilian splitting test. Energy Procedia 139, 266–272. Alwaeli, M., 2017. Investigation of gamma radiation shielding and compressive strength properties of concrete containing scale and granulated lead-zinc slag wastes. J. Clean. Prod. 166, 157–162. Amparano, F.E., Xi, Y., Roh, Y.S., 2000. Experimental study on the effect of aggregate content on fracture behavior of concrete. Eng. Fract. Mech. 67, 65–84. Appa Rao, G., Raghu Prasad, B.K., 2011. Influence of interface properties on fracture behaviour of concrete. Indian Acad. Sci. 36, 193–208. Beygi, M.H.A., Kazemi, M.T., Vaseghi Amiri, J., Nikbin, I.M., Rabbanifar, S., Rahmani, E., 2014a. Evaluation of the effect of maximum aggregate size on fracture behavior of self compacting concrete. Constr. Build. Mater. 55, 202–211. Beygi, M.H.A., Kazemi, M.T., Nikbin, I.M., Vaseghi Amiri, J., Rabbanifar, S., Rahmani, E., 2014b. The influence of coarse aggregate size and volume on the fracture behavior and brittleness of self-compacting concrete. Cement Concr. Res. 66, 75–90. BS 8500-1, 2006. Method of Specifying and Guidance for the Specifier. Chen, B., Liu, J., 2004. Effect of aggregate on the fracture behaviour of high strength concrete. Constr. Build. Mater. 18, 585–590. Ç ullu, M., Bakırhan, E., 2018. Investigation of radiation absorption coefficients of leadzinc mine waste rock mixed heavy concrete at 662–1460 keV energy range. Constr. Build. Mater. 173, 17–27. Ç ullu, M., Ertas, H., 2016. Determination of the effect of lead mine waste aggregate on some concrete properties and radiation shielding. Constr. Build. Mater. 125, 625–631. Demir, F., Budak, G., Sahin, R., Karabulut, A., Oltulu, M., Serifoglu, K., Un, A., 2010. Radiation transmission of heavyweight and normal-weight concretes containing colemanite for 6MV and 18MV X-rays using linear accelerator. Ann. Nucl. Energy 37, 339–344. Demir, F., Budak, G., Sahin, R., Karabulut, A., Oltulu, M., Un, A., 2011. Determination of radiation attenuation coefficients of heavy weight and normal-weight concretes containing colemanite and barite for 0.663 MeV γ-rays. Ann. Nucl. Energy 38, 1274–1278. Elices, M., Rocco, C.G., 2008. Effect of aggregate size on the fracture and mechanical properties of a simple concrete. Eng. Fract. Mech. 75, 3839–3851. Elsharief, A., Cohen, M.D., Olek, J., 2003. Influence of aggregate size, water cement ratio and age on the microstructure of the interfacial transition zone. Cement Concr. Res. 33, 1837–1849. Esen, Y., Do� gan, Z.M., 2018. Investigation of usability of limonite aggregate in heavyweight concrete production. Prog. Nucl. Energy 105, 185–193. Esen, Y., Yilmazer, B., 2010. Investigation of some physical and mechanical properties of concrete produced with barite aggregate. Sci. Res. Essays 5, 3826–3833. Esen, Y., Yilmazer, B., 2011. An investigation of X-ray and radio isotope energy absorption of heavyweight concretes containing barite. Bull. Mater. Sci. 34, 169–175. Ezeldin, A.S., Aitcin, P.C., 1991. Effect of coarse aggregate on the behavior of normal and high-strength concretes. Cem. Concr. Aggregates 13, 121–124.
19
Omid. Lotfi-Omran et al.
Progress in Nuclear Energy 121 (2020) 103222 Vishalakshi, K.P., Revathi, V., Sivamurthy Reddy, S., 2018. Effect of type of coarse aggregate on the strength properties and fracture energy of normal and high strength concrete. Eng. Fract. Mech. 194, 52–60. Vu, X.H., Daudeville, L., Malecot, Y., 2011. Effect of coarse aggregate size and cement paste volume on concrete behavior under high triaxial compression loading. Constr. Build. Mater. 25, 3941–3949. Wood, J., 2013. Computational Methods in Reactor Shielding. Elsevier. Wu, K., Chen, B., Yao, W., 2001. Study of the influence of aggregate size distribution on mechanical properties of concrete by acoustic emission technique. Cement Concr. Res. 31, 919–923. Xiao, J., Schneider, H., Donnecke, C., Konig, G., 2004. Wedge splitting test on fracture behaviour of ultra high strength concrete. Constr. Build. Mater. 18, 359–365. Yang, K.H., Mun, J.S., Lee, H., 2014. Workability and mechanical properties of heavyweight magnetite concrete. ACI Mater. J. 111, 273–282. Yılmaz, E., Baltas, H., Kırıs, E., Ustabas, I., Cevik, U., El-Khayatt, A.M., 2011. Gamma ray and neutron shielding properties of some concrete materials. Ann. Nucl. Energy 38, 2204–2212.
Singh, C., Singh, T., Kumar, A., Mudahar, G., 2004. Energy and chemical composition dependence of mass attenuation coefficients of building materials. Ann. Nucl. Energy 31, 1199–1205. Sliwinski, J., Tracz, T., 2013. Cement paste content as the factor influencing on compressive and splitting tensile strength of concrete. Cem. Lime Concr. 6, 353–361. Talaei, S., Jafari, M., Tarfan, S., 2014. The effect of ratio of aggregate to cement paste volume on structural lightweight concrete strength, viscosity, density and cost. Res. J. Environ. Earth Sci. 6 (9), 443–450. Tasdemir, C., Tasdemir, M.A., Lydon, F.D., Barr, B.I.G., 1996. Effects silica fume and aggregate size on the brittleness of concrete. Cement Concr. Res. 26, 63–68. Tijani, S.A., Kamal, S.M., Al-Hadeethi, Y., Arib, M., Hussein, M.A., Wageh, S., Dim, L.A., 2018. Radiation shielding properties of transparent erbium zinc tellurite glass system determined at medical diagnostic energies. J. Alloy. Comp. 741, 293–299. Tracz, T., Sliwinski, J., 2012. Effect of cement paste content and w/c ratio on concrete water absorption. Cem. Lime Concr. 3, 131–137. Uddin, M.T., Mahmood, A.H., Kamal, M.D.R.I., Yashin, S.M., Zihan, Z.U.A., 2017. Effects of maximum size of brick aggregate on properties of concrete. Constr. Build. Mater. 134, 713–726.
20