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Study characteristics of new concrete mixes and their mechanical,
physical and gamma radiation attenuation features
Moamen G. El-Samrah1, Mohamed A.E. Abdel-Rahman1, and Amr M.I. Kany2
1 Nuclear Engineering Department, Military Technical College, Kobry El-kobbah, Cairo, Egypt
2 Physics Department, Faculty of Science, Al-Azhar University, Cairo, Egypt
ABSTRACT
Ordinary concrete and those of different compositions are regarded as suitable material in many applications that
concerned with gamma and neutron radiation shielding purposes. They are widely used in nuclear power plant,
medical facilities, nuclear shelters and for radioactive materials transportation as well as storage of radioactive
wastes. In this study four different concrete mixes were prepared with the following different types of coarse
aggregates: dolomite, barite, goethite and steel slag. The effect of changes in the fine aggregates, selected to be
50% local sand and 50% limonite with the addition of 10% silica fume (SF) and 10% fly ash (FA) by replacement
of the total cement weight, on the performance of the samples was also investigated. To examine the performance
of such samples for radiation shielding applications, a set of physical, mechanical and radiation attenuation
properties was studied and compared with those of ordinary concrete. This investigation includes compressive
strength, slump test, bulk density, ultrasonic pulse velocity test and gamma rays attenuation measurements for the
different samples. A verification of the experimental results concerning the radiation attenuation measurements
was performed using WinXcom program (Version 3.1). The experimental results revealed that all concrete mixes;
goethite-limonite concrete (G.L), barite-limonite concrete (B.L), steal slag-limonite concrete (S.L) and dolomite
concrete (D.C) had good physical and mechanical properties that successfully satisfying them as high
performance concretes. In addition the barite-limonite and the steal slag-limonite have the higher γ-ray attenuation
coefficients at low and high energy range and hence have a better radiation shielding. The obtained results from
WinXcom program calculations showed a good agreement with the experimental results concerning γ-ray
attenuation measurements for the studied concrete mixes.
Keywords: High performance concrete, Radiation shielding, Mass attenuation coefficient (μm) and WinXcom
program.
1. Introduction
Radiation is a general word that was used frequently in the past decades to describe electromagnetic
waves but nowadays radiations refer to the all kinds of electromagnetic waves in addition to the atomic
and subatomic particles that have been discovered . One of many types of classifications that organizes
and classifies the different types of radiation indicates that radiation can be divided into two major
categories. The first is the non-ionizing radiation and the second is the ionizing radiation. In shielding
issues, we concerned with the ionizing radiation especially the indirect ionizing radiation (γ-rays and
neutrons), because the direct ionizing radiation (α, β, P,….) is considered as small external threat as this
type includes charged particles which known with their small ranges in the medii through which they
pass so, they lose their full energies in quite small ranges . The serious problem always is in the indirect
ionizing radiation since they have high penetrating ability and longer ranges. Hence any shield that can
attenuate them to the desired level will automatically attenuate the others to negligible value. In
attenuating gamma radiation only high (z) elements are preferred thus dense materials are required like
steel and lead for example. However, in attenuating neutrons, especially fast neutrons, light elements
like hydrogen and oxygen are needed and as a conclusion from the former, the shielding barrier should
have high density and in the same time high hydrogen or light elements content so, considering this
conflict, the optimum shielding barrier can be used in this case is concrete especially heavy weight
* Corresponding author e-mail: mabdelrahman@mtc.edu.eg, Phone: 0122 2431122

concrete which achieves a good compromise between the high density and high hydrogen content that
gives heavy weight concrete the priority in attenuating gamma and neutrons in the same time. Heavy
weight concrete is widely used as a shielding barrier in nuclear power plants, nuclear shelters,
radiotherapy-megavoltage rooms and for transporting as well as storing radioactive wastes . To achieve
the desired physical, mechanical and radiation attenuation properties, the selection of local suitable
aggregates and additives from which the shield is to be made becomes of great importance . Some of the
natural minerals used as coarse and fine aggregates in heavy weight concrete are hematite, magnetite,
ilmenite, barite, limonite, goethite, serpentine and some of the artificial synthetic aggregates include
materials like iron shots, steel punching, iron fibers, heavy slag and boron frits. It is essential that
aggregates used in heavy weight concrete must be inert with respect to alkalis and have good
mechanical-physical properties to obtain adequate mix . The main aim of this research is to investigate
the suitability of some different mixtures with different types of coarse aggregates for yielding high
performance heavy weight concrete that could enhance the attenuation properties and thus the shielding
efficiency against X-rays and γ-rays.
2. Methodology of research
2.1) Materials
In this study, the aggregates selected were chosen regarding the radiation shielding point of view and in
the same time satisfy the requirements of construction applications. Consequently, four different types of
course aggregates were used , dolomite [CaMg(CO3)2] from Helwan, Egypt, goethite [α-FeO(OH)] and
barite [BaSO4] both from El-Bahariya Oasis, Western Desert, Egypt, steel slag (by product from iron
industry) obtained from Iron and Steel Factory, Eltebin, Helwan, Egypt. The fine aggregates used are
local sand, Helwan, Egypt and limonite [Fe2O3 ˙ nH2O] from El-Bahariya Oasis, Western Desert, Egypt.
The materials used in this study are Portland blast furnace slag cement CEM/B-S 42.5 N which is
compatible with ASTM C-150 , from El-Aamryah Cement Company, Egypt. The additives used are fly
ash (FA) class F, silica fume (SF) and super plasticizer Sikament-NN (type G) all from Sika Company,
El-Obour, Egypt. Coarse and fine aggregates were sieved in order to get coarse aggregates in the range
5-20 mm and fine aggregates with particle size <5 mm. Some important physic-mechanical properties of
aggregates are presented in table 1 and evaluated according to the limits stated by . Chemical analysis
was performed for aggregates, cement and additives using XRF spectrometer as shown in Table 2
Table 1: Some important physical and mechanical properties of coarse and fine aggregates
Property Barite Goethite Steel slag Dolomite Limonite Sand
Specific gravity 4.4 4.04 4.46 2.68 2.22 2.65
Water absorption, % 1.5 13.5 0.52 0.7 30.8 0.4
Crushing value, % 63.3 20 16.83 - - -
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Table 2: Chemical analysis for cement, additives and aggregates
Oxides PBFSC SF FA Coarse aggregates Fine aggregates
Goethite Barite Steel Slag Dolomite Limonite Sand
SiO223.33 96.81 61.13 11.2 1.16 8.13 2.24 16.3 94.84
Al2O35.91 0.25 27.68 3.39 0.64 2.01 0.95 2.97 2.12
Fe2O33.29 0.45 4.15 67.0 20.84 37.0 0.61 68.1 0.82
CaO 57.07 0.16 1.32 6.49 1.59 44.4 37.9 4.16 0.52
MgO 3.10 0.26 0.44 0.992 1.63 1.15 15.03 0.643 0.1
SO3-- 2.9 0.14 0.28 1.9 4.42 0.864 0.39 2.9 0.11
Cl-0.03 0.03 0.07 0.923 0.41 0.15 0.13 0.62 0.06
Na2O 0.24 0.14 0.15 1.46 - 0.973 0.25 0.985 0.27
K2O 0.25 0.28 0.85 1.8 0.34 0.358 0.07 0.74 0.69
TiO20.08 - 2.07 1.49 - 1.08 0.13 1.28 0.12
BaO - - 0.04 - 66.77 - - - -
P2O5- 0.03 0.61 0.91 0.28 1.74 0.03 0.83 0.05
V2O5- - - - - 0.104 - - -
Cr2O3- - - 0.416 0.14 0.167 - - -
MnO - 0.05 - 0.292 1.1 1.82 - - -
CeO2- - - 0.278 - - - - -
Sm2O5- - - 0.314 - - - 0.168 0.06
L.O.I 2.97 0.95 0.85 0.3 0.2 - 42.25 0.15 0.1
Total 99.17 99.55 99.64 99.15 99.52 99.94 99.94 99.84 99.86
2.2) Mix proportions
Four different concrete mixes were prepared using goethite, barite, dolomite and steel slag as coarse
aggregates. Fine aggregates used in all mixes (except D.C mix) were (50% local sand – 50% limonite) in
addition to 10% silica fume (SF) and 10% fly ash (FA) as a partial replacement from the total cement
content. All concrete mixes were prepared according to the American Concrete Institute method (ACI)
of absolute volumes . The ACI method is generally considered to be more convenient and suitable for
heavy weight concrete. The mix proportions per 1m3 for all concrete mixes are shown in Table 3. All
aggregates used in this study were used in saturated surface dry form to eliminate the effect of water
absorption during mixing in order to evaluate the real effect of aggregates on concrete mixes properties .
The water to cement ratio for all mixes were set to be 0.43.
Table 3: Mix proportions of concrete mixes
Mixes
Concrete ingredients, kg/m3
PBFSC
Fine aggregates Coarse aggregates Additives S.P
Sand Limonite Goethite Barite Steel
slag Dolomite SF FA
G.L 400 270.77 226.83 1651.3 - - - 50 50 12.5
B.L 400 270.77 226.83 - 1798.3 - - 50 50 12.5
S.L 400 270.77 226.83 - - 1822.86 - 50 50 12.5
D.C 500 554.8 - - - - 1126.3 - - -
2.3) Mixing, curing and testing specimens
The mixing method used for the concrete mixes in this study is similar to that used for conventional
concrete. The materials were mixed using a mixer with a capacity of 56 dm 3. The mixing sequence for
each mix was as follows; dry mixing of coarse aggregates and fine aggregates, followed by cement
mixed with mineral cementing materials for 2 min, adding of 80% of the mixing water with the dry
mixture for 1.5 min, the rest 20% of the mixing water was added to the rotating mixer in a gradual
matter. All mixes were mixed for 5 min in order to prevent fresh concrete from segregation. Slump test
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was performed on the fresh concrete to evaluate the workability according to ASTM C143 standard . All
concrete specimens were cast in three 10×10×10 cm cubic molds and cylindrical molds [20 cm in
length– 10 cm in diameter]. After casting the specimens in their molds, the specimens were consolidated
using a vibrating table, then the specimens were covered to avoid water evaporation and kept for 24
hours. After removing specimens from their molds, they were cured by immersing them in curing tanks
until the date of testing.
2.4) Slump test
The slump test is an indication on the behavior of a compacted inverted cone of fresh concrete under the
action of gravity. It measures the consistency or the wetness of concrete. It is also a simple method to
evaluate the workability of the prepared concrete.
2.5) Bulk density
For concrete, expressing the density in kilograms per cubic meter is widely common when aggregates
are to be actually batched by volume and here the density to be calculated is called bulk density. The
bulk density for hardened concrete mixes was performed according to ECCS 203-2001code .
2.6) Compressive strength
The compressive strength of concrete is usually determined by applying a uniformly distributed
increasing compression load on a cubic specimen using suitable testing equipment until failure. The
testing equipment used for this test is 2000 KN universal machine. The test was performed using a set of
three cubic specimens [10×10×10 cm3] for each concrete mix at curing age 28 days and the compressive
strength at 90 days was estimated using the following general equation:
(σc)t (1)
Where: (σc)t and are the compressive strength of concrete at any age t days and at 28-days,
respectively. Both a and b are the coefficients which are varied for different cements and curing
conditions. According to ACI 209/71 standard, this equation was obtained as a result of a study of
concrete strength versus time with different types of concrete . The constants a and b are related to the
characteristics of the used mix design and curing conditions and they could be determined by solving
two simultaneous equations at two different ages using previous experimental work which was suitable
and agreeable with the concrete mixes used in this study .
2.7) Ultrasonic pulse velocity test
This test considered as a good and easy technique for assessment of concrete quality by measuring the
velocity of the ultrasonic pulse that passing through a known thickness of the concrete specimen
according to ASTM C597 . The ultrasonic pulse velocity test is used mainly to measure the concrete
quality however; it can be used to confirm the compressive strength test results.
2.8) Calculation of elastic modulus
Modulus of elasticity aims to measure the concrete resistance being deformed elastically when a load is
applied to it, also it can be defined as the slope of the stress strain curve for concrete in the elastic
deformation region . By increasing the modulus of elasticity, the concrete becomes stiffer, harder and
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resistant to deformation and excessive loads. In this study elastic modulus for concrete mixes were
calculated using the following practical (semi-empirical) equation:
(2)
Where: σ is the compressive strength after 28 days, γ is the concrete density, k1 the correction factor for
coarse aggregates ranges from 0.95 to 1.2 and k2 the correction factor for mineral additions ranges from
0.95 to 1 .
2.9) Gamma rays attenuation measurements
In this study, cylindrical samples of dimensions 20 cm in length and 10 cm in diameter were prepared
for all concrete mixes and then cut to different thicknesses. The gamma ray sources used in these tests
are Ba-133, Cs-137 and Co-60 with four gamma lines and their specifications are given in Table 4.
Table 4: Energies and activities of gamma sources used in the measurements
Gamma lines (keV) 356 662 1173 - 1332
Production Date 2014 2014 2013
Initial Activity (µCi) 10 10 6.95
The emitted gamma rays from the sources were detected and measured using NaI(Tl), 3’’x3’’,
scintillation detector with multichannel analyser using software (UCS-30) version 1.1.06 USB,
Spectrum Technique 2010. To achieve a good geometry condition, the gamma source was placed inside
3 cm lead holder (source collimator) with an aperture of 3 mm in diameter, while the scintillation
detector had been surrounded by blocks of lead (detector collimator) to prevent scattered gamma rays
from entering the detector to get a more precise measurements. The gamma ray beam, the samples and
the detector were placed in the same horizontal plane and the distance between the source and the face
of the detector was 31 cm fixed for all measurements as shown in Fig.1. The attenuation coefficient for
each sample was determined by measuring the intensity of γ-ray transmitted from different thicknesses
by applying the Lambert equation:
(3)
where: Ix is the transmitted γ-ray intensity, Io is the incident intensity of γ-rays, μm is the mass attenuation
coefficient (cm2/g) and ρx is the density thickness (g/cm2).. By plotting a graph between ln (Ix/I0) and
density thickness (ρx) for each concrete sample, the obtained results were straight lines with gradients
represent the values of mass attenuation coefficients for the mix at specific energies.
The half value layer (HVL) and the tenth value layer (TVL) for each concrete mix was also obtained
from the following equation .
(4)
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Graphs of the mass attenuation coefficients at different gamma energies for different concrete mixes
were plotted and compared with the accepted graph obtained by using WinXcom program (version 3.1)
Figure 1: Schematic diagram for the gamma rays attenuation measurements
3. Results and Discussion
3.1) Slump test results
The results of the slump tests of the investigated concrete mixes were ranged from 6 cm to 10 cm as
shown in Table 5, which means that all mixes were accepted from the workability point of view . The
highest slump values obtained with D.C and B.L mixes respectively and the lowest value obtained with
G.L mix. These results can be attributed mainly to the differences in the water absorption ratios of the
different aggregates in addition to the high specific gravity values for the used coarse aggregates except
for dolomite used in D.C mix (see Table 2).
Table 5: Slump values for the concrete mixes.
Concrete mix G.L B.L S.L D.C
Slump value, cm 6.0 8.0 7.5 10.0
3.2) Bulk density
The bulk densities of the concrete mixes are shown in Table 6. The results obtained were logic as the
bulk density of the prepared concrete is directly proportional to the specific gravity of the aggregates
used in the mix design (see Table 2); therefore, S.L mix was found to have the highest value of bulk
density. Moreover, S.L, B.L and G.L can be classified as heavy weight concrete because all of them
were found to have bulk density values more than 2600 kg/m3 . On the other hand D.C approached to be
heavy weight concrete as its density was 2570 kg/m3.
Table 6: Bulk densities of the studied concrete mixes
Concrete mix G.L B.L S.L D.C
Bulk density, kg/m32906 2963 2994 2570
3.3) Compressive strength
After curing for 28 days, the concrete mixes gained the most of their strength because of the formation
of the hydration products and the domination of hydrated calcium silicate (C-S-H gel) among these
hydration products. The compressive strength of all concrete mixes was higher than that of traditional
concrete. Using Portland blast furnace slag cement with high content was one of the reasons that lead to
the production of high strength concrete mixes, also the addition of fly ash and silica fume (see Table 3)
participated in the development of the strength of the mixes due to their good filling effect and the
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pozzolanic activity. The compressive strength of the different concrete mixes at 28 days and 90 days
(estimated) is plotted in Fig. 2. The results obtained revealed that D.C and S.L mixes were significantly
higher than the G.L and B.L mixes and the differences could be attributed to the physic-mechanical
properties of the coarse and fine aggregates used (see Table 2). The use of limonite as a portion of the
fine aggregates was due to its good neutron shielding properties but it had a bad effect on the strength of
the mixes because its high water absorption value. The relatively small crushing value and high specific
gravity (4.04) had good effects on gaining strength in G.L mix but on the other hand its high water
absorption value (13.5%) curtail this effect. The high crushing value of barite (63.3%) had a significant
bad effect on the B.L strength even if its low water absorption value (1.5%) and high specific gravity
(4.4). the high specific gravity of steel slag (4.46) and its good physic-mechanical properties in addition
to the porous structure all that enhanced the strength of the S.L mixes in spite of using limonite as a
portion of the fine aggregates in the mix. Using sand only as fine aggregate and dolomite as coarse
aggregate in D.C mix had a good effect on the strength due to their low water absorption values (0.4%,
0.7%) respectively, and the convergence in the specific gravity values of both of them which had a great
effect on strengthening the physical bonds between them and also with the binder.
Fig 2: Compressive strength of the concrete mixes. Fig 3: Ultrasonic pulse velocity values for the concrete mixes.
3.4) Ultrasonic pulse velocity test
This test was performed to assess the quality of concrete represented in uniformity, homogeneity,
presence or absence of cracks and durability. Additionally, the obtained results from this test confirm
those obtained from the compressive strength test. The results plotted in Fig. 3 showed that all concrete
mixes in this study classified as excellent in quality because all of them have ultrasonic pulse velocity
higher than 4500 m/sec . Furthermore, these results showed a high agreement with those obtained from
compressive strength test.
3.5) Modulus of elasticity
As shown in Fig 4, all mixes in this study have modulus of elasticity greater than that for ordinary
concrete (i.e. ~30 Gpa) so all concrete mixes are stiffer, harder and resistant to deformation and
excessive loads.
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Figure 4: Elastic modulus values for the concrete mixes.
3.6) Gamma rays attenuation measurements
The aim of this part was to investigate the gamma attenuation properties for the concrete mixes used in
this study and to determine the best mix among all the mixes.
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Figure 5: Relation between ln ( ) versus barrier density thickness (ρx) for the four concrete mixes.
Fig. 5 shows the relation between ln (Ix/I0) and barrier density thickness (ρx) for the four concrete mixes.
Moreover, graphs of (μm) against Eγ were plotted together with the calculated values of μm that obtained
using WinXcom program (version 3.1) for the four concrete mixes as shown in Fig. 6. The deduced
values of mass attenuation coefficient (μm), HVL and TVL for all mixes are shown in Table 7.
Results show that B.L mix has the greatest linear attenuation coefficient against gamma rays of energies
356 and 662 keV and thus the corresponding minimum required HVL for these energies. The reason
could be due to the high atomic number of barium (56) which is the effective element of the barite ore
used as coarse aggregate in B.L mix. The photo electric effect has a significant contribution in the
attenuation process at these energies and hence the microscopic attenuation cross section since the photo
electric effect is directly proportional to (Zn) where n varies from 4-5, so with the high (Z) value of
barium (56) which is greater than the double of that for iron (Z=26), explains the priority of B.L mix on
S.L mix at the gamma energy lines; 356 and 662 keV. On the other hand, at the gamma energies 1173
and 1332 keV, S.L mix regain its priority on B.L. This is due to its higher bulk density, the very small
contribution of the photo electric effect in this energy range since the dominant mechanisms of the
interaction are belong to Compton scattering and pair production that are directly proportional to Z (the
number of electrons existing in the absorbing material).
Figure 6: Relation between mass attenuation coefficients versus gamma energy for the four concrete mixes.
9
a) G.L mix
EeV
0.2 0.4 0.6 0.8 1.0 1.2 1.4
Mass attenuation coefficient ( ), cm 2/g
0.02
0.04
0.06
0.08
0.10
0.12
Exp.values
Calc.values
b) B.L mix
EeV
0.2 0.4 0.6 0.8 1.0 1.2 1.4
Mass attenuation coefficient ( ), cm2/g
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Exp. values
Calc. values
d) D.C mix
E eV
0.2 0.4 0.6 0.8 1.0 1.2 1.4
Mass attenuation coefficient ( ), cm 2/g
0.02
0.04
0.06
0.08
0.10
0.12
Exp. values
Calc. values
c) S.L mix
EeV
0.2 0.4 0.6 0.8 1.0 1.2 1.4
Mass attenuation coefficient ( ), cm 2/g
0.02
0.04
0.06
0.08
0.10
0.12
Exp. values
Calc. values

Table 7: The obtained values of mass attenuation coefficient (μm) and HVL for the four concrete mixes
Property Mass attenuation coefficient (μm), cm2/g HVL, cm
Gamma
Energy, keV 356 662 1173 1332 356 662 1173 1332
G.L mix 0.087±0.0045 0.075±0.0032 0.057±0.0038 0.055±0.0037 2.74±0.096 3.18±0.094 4.17±0.193 4.33±0.202
B.L mix 0.111±0.0064 0.087±0.0037 0.058±0.0031 0.056±0.0032 2.11±0.084 2.68±0.078 4.02±0.152 4.17±0.171
S.L mix 0.091±0.0046 0.075±0.0034 0.060±0.0034 0.059±0.0022 2.55±0.088 3.08±0.095 3.85±0.151 3.92±0.104
D.C mix 0.096±0.0042 0.084±0.0037 0.060±0.0029 0.057±0.0028 2.81±0.085 3.21±0.097 4.50±0.149 4.75±0.165
4. Conclusion
The results reported in this study investigate the influence of coarse (dolomite, barite, goethite and steel
slag) and fine aggregates on the performance of concrete as radiation shielding barriers. Both D.C and
S.L mixes show the best physical and mechanical properties among the studied concrete mixes interms
of low water absorption, specific gravity values (for D.C dolomite and sand have approximately similar
values which prevent the segregation however steel slag has a high specific gravity value which leads
the S.L to have a high bulk density) and acceptable crushing factor. On the other hand both B.L and G.L
mixes show a slight decrease in the physic-mechanical properties due to the low crushing value of barite
and the high water absorption value of goethite, respectively. However they are still successfully fulfil
the required properties set out within the international standards, where barite and goethite have, some
advantages over their counterpart, high specific gravity values. Additionally, using limonite as a portion
of fine aggregates in G.L, B.L and S.L concrete mixes had a bad effect on the physic-mechanical
properties for these mixes due to its high water absorption value, while it enhances the gamma
attenuating properties for these mixes.
The high specific gravity values of steel slag, barite and goethite as well as the presence of effective
elements that have high Z number like iron and barium give the priority of S.L, B.L and G.L mixes on
D.C mix in attenuating gamma rays. The obtained results confirmed that B.L mix was the best concrete
mix in attenuating gamma rays in both low and intermediate energies however S.L mix proved to be the
best one in attenuating gamma rays at higher energies.
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