Effect of Flyash Addition on Mechanical and Gamma Radiation Shielding Properties of Concrete

Six concrete mixtures were prepared with 0%, 20%, 30%, 40%, 50%, and 60% of flyash replacing the cement content and having constant water to cement ratio. The testing specimens were casted and their mechanical parameters were tested experimentally in accordance with the Indian standards. Results of mechanical parameters show their improvement with age of the specimens and results of radiation parameters show no significant effect of flyash substitution on mass attenuation coefficient.


Introduction
With the increasing applications of radioactive isotopes in several fields of science and technology, there arises the need of using them with extreme care, only after having proper shielding.Efficiency and cost of the material are the two factors that are primarily taken care of, for selecting any material for field applications.Concrete is the most widely used material for shielding gamma radiations satisfying the guidelines.It is used in abundance, particularly due to its good radiation shielding and mechanical properties [1].Concrete has structure heterogeneous in nature and the origin of its peculiar characteristics is its internal structure.The structure/microstructure variation for a material is a very important factor which plays a crucial role in determining the mechanical properties and its deformation behaviour.The knowledge of complex relation between properties of concrete ingredients and its structure assists in preparing concrete mixture according to the requirements as it has lasting effect on workability, early strength, shrinkage of hardened concrete, and permeability characteristics of concrete.
To make cost effective concrete, research has been carried out to use minimum amount of cement and aggregates and utilise by-products in as much quantity as possible.Ground blast furnace slag, silica fume, foundry sand, cement kiln dust, and flyash are the major materials that have been tested as an alternative of cement.Among the various admixtures, flyash is most suitable due to its pozzolanic nature.Not only does flyash play the role of filler but it also has the properties of a binder.It reacts with free lime liberated during the hydration of cement resulting in positive effect on late age strength of concrete.It is particularly suitable to use in mass concrete applications where the cement requirement is large.
The properties of fresh and hardened concrete have been studied in detail by various workers.Workability, slump loss, setting time, bleeding, segregation, and a number of related practical issues are addressed among the properties of fresh concrete [2][3][4][5].Among the hardened concrete properties, compressive strength and other mechanical and physical properties of hardened concrete such as tensile strength, elastic properties, shrinkage, creep, cracking resistance, electrical and thermal transport, and other properties were studied [6][7][8][9][10][11][12][13][14][15].Also the effects of addition of flyash in preparing concrete on the quality, workability, and durability were studied.Durability of concrete having certain amount of flyash in place of cement was superior to concrete without flyash [16][17][18], the effect of flyash incorporation on the water demand was reported [19][20][21], the compressive strength of flyash concrete showed continuous improvement with age [22][23][24][25], and early shrinkage behaviour of flyash concrete was studied [26,27].The above reported effects of flyash addition to concretes are due to suitable changes in the structure of concretes.
The interaction of gamma radiation with matter has been studied in the past by several workers in concretes with the help of different interaction parameters such as mass attenuation coefficients [28][29][30][31][32][33].Flyash was studied as a radiation shielding material for gamma rays and reported that it if compacted to high degree it can be used for shielding [34].
In this study, concrete specimens were prepared with flyash substituting different percentages of cement.The mechanical properties, slump, compressive strength, flexural strength, and modulus of elasticity, were measured for the prepared samples.Along with these mechanical properties, the radiation interaction parameters, namely, linear and mass attenuation coefficient, were also calculated for the prepared specimens.1 as specified by Indian specifications IS: 8112-1989 [35].Flyash used in the study was obtained from thermal power plant, Bathinda.Flyash used was of Class F type (CaO < 10%).Fine aggregate (natural sand) used in this study was having 4.75 mm maximum size.Coarse aggregate (gravel) used in this study was of 12.5 mm nominal size.The results of physical properties and sieve analysis are given in Table 2. Potable water was used as mixing water for preparation of specimens.

Methods.
Six concrete specimens were prepared.One mixture was made without using flyash and other mixtures were made with flyash as a replacement for cement by weight.Cement was replaced with 20%, 30%, 40%, 50%, and 60% of flyash by weight.The mixture proportion (kg/m 3 ) of prepared concrete specimens is shown in Table 3.The concrete samples were prepared with same water to cementitious ratio./ = 0.40 was taken for preparing samples.This ratio was taken as constant, so as to only investigate the effect of flyash addition to the ordinary concrete.The prepared samples were named as OC1, OC2, OC3, OC4, OC5, and OC6, in which 0%, 20%, 30%, 40%, 50%, and 60% of flyash have replaced the cement content.
The test specimens were prepared according to specifications of IS: 516-1959 [36].Concrete cubes of 150 mm in size were casted for testing compressive strength of specimens.Test specimens of 100 × 100 × 500 mm beams were casted for testing flexural strength.Test specimens of 150 × 300 mm cylinders were casted for testing modulus of elasticity.They were kept in casting room for 24 hours at a temperature about 25 ∘ C.They were demolded after 24 hours and then put into water bath until the time of testing [37].At the end of curing period, several tests were done on test specimens to determine some of their mechanical properties and the results obtained are shown in the following section.
The mass attenuation coefficients of all six concretes have been calculated with the help of winXCOM, a computer

Theory
Workability of fresh concrete is defined by two parameters, homogeneity and consistency.Homogeneity was checked by the uniform distribution of constituents and consistency was checked by slump cone test.
Compressive strength is the capacity of concrete to withstand axially directed pushing forces.It is a measure of force that can be applied to the concrete before it cracks or fails.The flexural strength estimates the load under which the cracking will develop.The modulus of elasticity, also known as secant modulus, is calculated for 33% of the maximum stress.It reflects the ability of the concrete to deform elastically.
When a beam of monochromatic radiations passes through matter, the intensity of the beam is reduced to some extent.The decrease in intensity of radiation from   to  is given by Lambert-Beer law: where  is density of target sample,  is the thickness of target sample, and / (cm 2 /gm) is mass attenuation coefficient, denoted by   .For a compound or mixture, it is given by where   and (/)  are the weight fraction and mass attenuation coefficient, respectively, of the constituent element .
The linear attenuation coefficient,  (cm −1 ), was calculated by multiplying   by the density of samples.1(a) and 1(b) that the early age strength of flyash concrete is less than the anticipated value and it goes on increasing with the passage of time.We can also conclude that the continuous strength gain of flyash concrete increases more with the elapsing of time than for ordinary concrete without flyash.

Results and Discussion
The effect of flyash addition to ordinary concretes for all the six specimens on the compressive strength of specimens with age of 7, 28, and 91 days by compression testing machine is shown in Figure 2. The compressive strength of concrete at a given age under given curing conditions depends mainly on water to cementitious ratio and varies in accordance with Abram's law [39] defining the relation between compressive strength and / ratio.Figure 2 shows that the compressive strength of prepared specimens decreases with the addition of flyash in place of cement and it decreases with the increase in flyash content.This conclusion is true for any number of days of testing.The compressive strength of OC1 concretes decreased by 75% after 7 days, 59% after 28 days, and 56% after 91 days with flyash replacing cement by 60%.Also the reduction in compressive strength is enhanced by 143% after 28 days and 183% after 91 days for concrete having 60% flyash in place of cement instead of increase of 46% after 28 days and by 59% after 91 days for ordinary concrete.The compressive strength results show that flyash concrete mixtures can be used for structural purposes, although lower compressive strength results for flyash concretes are obtained as the strength will increase with age.

Flexural Strength.
The flexural strength of the prepared samples was determined at the age of 7, 28, and 91 days.The results of the flexural strength variation for the replacement of cement with five different percentages of flyash with age are shown in Figure 3 and it clearly showed that the strength increased with number of days.As is clear from Figure 3, it decreased with an increase in flyash content in place of cement and it decreased by 50% after 7 days, 36% after 28 days, and 34% after 91 days for concrete containing 60% flyash in place of cement.Also the reduction in flexural strength is enhanced by 56% after 28 days and 67% after 91 days for concrete having 60% flyash in place of cement instead of increase of 21% after 28 days and by 26% after 91 days for ordinary concrete.As expected, the flexural strength of concrete is relatively low in comparison to the compressive strength.As the compressive strength of concrete increases with age, the flexural strength also increased but at a decreased rate.

Modulus of Elasticity.
It was determined for all the samples at the age of 7, 28, and 91 days.Figure 4 shows the elastic modulus development with time for the concrete specimens containing different percentages of flyash.The variation of modulus of elasticity with change in flyash content is similar to the variation of tensile strength.Figure 4 indicates that the modulus of elasticity reduced by 50% after 7 days, 36% after 28 days, and 34% after 91 days for concrete having 60% flyash in place of cement.Figure 4 clearly shows that the modulus of elasticity of concrete specimens increased with age of concrete.The reduction in elasticity modulus is enhanced by 56% after 28 days and 68% after 91 days for concrete having 60% flyash in place of cement instead of increase of 21% after 28 days and by 26% after 91 days for ordinary concrete.and the mass attenuation coefficient of concrete samples was calculated by WinXcom.
Figure 5 shows the variation of total mass attenuation coefficient,   , with energy for the chosen concretes in the wide energy range of 10 keV to 100 GeV.Also the experimental data of mass attenuation coefficient for six concrete specimens at 0.662 MeV has been marked in Figure 5.It is observed that   decreases sharply in the low energy region, then it becomes almost constant in the medium energy region, and it increases in the high energy region.Figure 5 shows that total mass attenuation coefficients decreased drastically with increasing photon energy in energy region 1 keV to 100 keV, it decreased slightly with increasing photon energy in energy region of 100 keV to 10 MeV, and it increased slowly and further becomes constant with increasing photon energy in energy region of 10 MeV to 100 GeV.This behaviour of   confirms the -dependence of different interaction processes in different energy regions and hence the variation of corresponding mass attenuation coefficients with energy.The results of mass attenuation coefficients confirmed that there is no effect on these radiation parameters (Table 5) with change in flyash content from 0% to 60% in place of cement.

Conclusions
From the undertaken study, the following conclusions can be drawn.
(1) There is well defined decrease in compressive strength results with an increase in cement content by flyash, but still the compressive strength results of flyash concretes were satisfactory and they can be used for construction purposes.
(2) The gain in compressive strength of flyash concretes after 28 days is more than in the case of ordinary concrete.With the increase in age of concrete, strength

Experimental
Photon energy (MeV)  (3) Tensile strength as well as modulus of elasticity of concretes decreases with an increase in flyash content.Decrease is quite less pronounced for the results of tensile strength than in case of modulus of elasticity.
(4) From results it is clear that, with change in flyash content, there is no change in mass attenuation coefficient of all the test specimens with electron density remaining constant.
(5) There is only slight variation in results of linear attenuation coefficient.The linear attenuation coefficient changes with flyash replacement as it is dependent on the density of mixtures.

Introduction:
When gamma radiation with matter, its intensity will decrease as it travels through matter.The decrease in intensity of radiation is dependent mainly on the type of target material and its thickness in its path.The attenuation properties of radiation for a particular target material are required to determine the amount of shielding necessary and how much dosage one would receive if that particular target material is used for the shielding.Concrete remains to be the first practical choice for radiation shielding for several reasons.Mehta and Monteiro (2006) asserted that concrete is used in abundance particularly for shielding purposes due to its good mechanical and radiation shielding properties.The determination of accurate values of interaction parameters is necessary before their usage in the field of industry, medicine, agriculture, tomography, etc. Mass attenuation coefficient is the basic parameter for studying gamma ray interactions with matter.Half value layer (HVL) and the effective atomic number are the two other important parameters for understanding the interaction with matter.
Lead is commonly used as gamma radiation shield but due to its cost and high density, it is not possible to use it on large scale.So in the past, different authors have studied various other construction materials for shielding of gamma radiations by evaluating their radiation parameters.One such material investigated commonly by researchers is concrete.Bashter (1997)  has been carried out to use minimum amount of cement and aggregates and utilize industrial by-products in as much quantity as possible with appropriate mechanical properties.One such available by-product is flyash, which has been used extensively for concrete formation due to its pozzolanic nature.Siddique (2004Siddique ( , 2009) studied utilization of flyash in concretes and concluded that flyash can be used as cement and sand replacement in ordinary concrete with satisfactory mechanical properties.Jiang and Malhotra (2000), Bouzoubaa et  Different authors have studied mechanical properties of concretes incorporating various admixtures but their behaviour as a radiation shielding material needs to be studied.So in the present study, lead concrete specimens were prepared with Class F flyash substituting different percentages of cement.The mechanical propertiesslump and compressive strength were measured for the prepared samples to check their consistency in practical field.Along with these mechanical properties, the radiation interaction parameters namely, linear and mass attenuation coefficient, half value layer, effective atomic number and electron density was also measured for the prepared specimens.Also the results of radiation parameters were compared with ordinary flyash concretes with same flyash variation in place of cement.

Theory
The water-cement ratio is the ratio of the weight of water to the weight of cement used in a concrete mix and has an important influence on the quality of concrete produced.It is given by expression: The hydration of cement reaction initiated by addition of water is responsible for binding concrete ingredients.W/C ratio largely determines the strength and durability of the concrete when it is cured properly.But this equation is only valid for concrete without any admixtures.So for accounting the use of various admixtures in concrete formation, the water to cementitious ratio is calculated by the expression where W is water content, C is cement content, F is flyash content, K is efficiency factor.The efficiency factor (K) is defined as the value of the particular ratio of the mass of cement to the mass of flyash for which they had an equivalent effect on the W/C ratio.
The ratio x is taken as a constant in this study so as to assess only the effect of variation in flyash content on radiation parameters.When a beam of monochromatic radiations passes through matter, the intensity of the beam is reduced to some extent.The decrease in intensity of radiation from I o to I is given by Lambert-Beer law: where ρ is density of target sample, x is the thickness of target sample and m/ρ (cm 2 /gm) is mass attenuation coefficient, denoted by m ρ .For a compound or mixture, it is given by where w i and (m/ρ) i are the weight fraction and mass attenuation coefficient, respectively, of the constituent element i.The linear attenuation coefficient, m (cm À 1 ) was calculated by multiplying m ρ by the density of sample.Half value layer is related to linear attenuation coefficient by the following relation The effective atomic number, Z eff is a parameter that characterizes the atomic number of composite material for different gamma ray interaction processes at different energies.The prepared concrete specimens cannot be marked by single atomic number.By considering actual atoms of a given molecule as identical (average) atoms having Z eff number of electrons, σ t a , ¼Z eff σ t el , .
So effective atomic number is defined by the relation where σ t a , and σ t el , are the average atomic cross-section and average electronic cross-section respectively.
Electron density, N e is defined as the number of electrons per unit mass.It can be calculated with the help of expression where M ¼∑ n A i i i is molar mass, N A is Avogadro number and n i is number of formula units of ith element.

Preparation of concrete mixtures
Ordinary Portland cement (43 Grade) was used as the main binder in casting samples (IS: 8112-1989).The flyash used in the study was obtained from thermal power plant, Bathinda.Natural sand (fine aggregate) used in this study was of 4.75 mm nominal size, while crushed stone (coarse aggregate) used in this study was of 12.5 mm nominal size (IS: 383-1970).The chemical composition of cement, sand, gravel and flyash was determined by Energy Dispersive X-ray Microanalysis (EDX), available at Thapar University Patiala.The mixtures were made with 0%, 20%, 30%, 40%, 50% and 60% of flyash as a replacement for cement by weight.The concrete samples were prepared with same water to cementitious ratio, W/C ¼0.40.This ratio was taken as constant so as to investigate only the effect of flyash addition to the lead concrete on the radiation properties.The compressive strength of concrete at a given age under given curing conditions depends mainly on water to cementitious ratio and varies in accordance with Abram's law (Abrams, 1919) defining the relation between compressive strength and w/c ratio.Potable water was used as mixing water for preparation of specimens.The mixture proportions of lead-flyash concretes are given in Table 1.
The test specimens were prepared according to specifications Bureau of Indian Satndards (IS: 516-1959).Firstly, the ingredients were weighed accurately and then mixed properly.After the sample has been remixed with water, cube moulds were immediately filled and concrete was compacted by hand.Any air trapped in the concrete reduces the strength of the cube.It has been found from the experimental studies that 1% air in the concrete approximately reduces the strength by 6%.Hence, the cubes were fully compacted.However, care was taken not to over compact the concrete as this may cause segregation of the aggregates and cement paste in the mix, which may ultimately also reduce the final compressive strength.Slump was measured by slump cone test having top diameter 10 cm, bottom diameter 20 cm and height 30 cm (IS: 1199-1959).The measured slump of control specimen was 76 mm.Plastic concrete having slump around this true value can fill the mould properly with good concrete quality.50 mm cube moulds were filled in three approximately equal layers.During the compaction of each layer, the strokes were distributed in a uniform manner over the surface of the concrete to eliminate air content.For subsequent layers, the compacting bar should pass into the layer immediately below.This proper tamping of the concrete mix eliminates the air content.After the top layer had been compacted, a trowel was used to finish off the surface level with the top of the mould.The moulds filled with mixture were kept in casting room for 24 h at a temperature about 25 °C.They were demolded after 24 h and then put into water bath until the time of testing compressive strength (Gambhir, 2011).The compressive strength tests for lead-flyash concretes were performed and the results indicate that flyash concretes have less strength at early ages but with the passage of time, it increases at a higher rate.
The prepared samples were named as LC1, LC2, LC3, LC4, LC5 and LC6 in which 0%, 20%, 30%, 40%, 50% and 60% of flyash have replaced the cement content.For the comparison of their attenuation properties with ordinary-flyash concretes, six ordinary concrete specimens were prepared with same variation of flyash in place of cement and were named OC1, OC2, OC3, OC4, OC4, OC5 and OC6 respectively.The weight fractions of different elements present in lead-flyash concretes and ordinary flyash concretes are shown in Tables 2 and 3.

Transmitted γ-ray spectra measurements
The narrow beam γ-ray transmission geometry was used for the attenuation measurements of prepared concrete specimens using 60 Co and 137 Cs.The radioactive sources were procured from Board of Radiation and Isotope Technology, Navi Mumbai, India.The experimental setup is shown in Fig. 1.The source was enclosed in a lead container with one face aperture 6 mm, placed behind the source collimator.Three collimators with apertures 6 mm, 4 mm and 2.8 mm were placed with their front faces at a distance 95 mm, 230 mm and 500 mm from source respectively.Hence, the incident beam divergence was 1.98°and the acceptance angle at the detector was 0.72°.Overall scatter acceptance angle was 2.70°.For this value of scatter acceptance angle, the scattered radiation reaching the detector can cause a ray-sum error of 0.5-1.0%,which is within the tolerating limits as reported by Midgley (2006).The width of each collimator was 40 mm.The prepared samples were cubes of side 50 mm.Samples were positioned at a distance of 280 mm from the source.The distance between the source and detector is 570 mm.To prevent the radiations scattered from walls reaching the detector, the whole set up was positioned at the centre of room and also the detector was surrounded with proper lead shielding.
The 3″ Â 3″ NaI(Tl) scintillation detector used in the study is a hermetically sealed assembly which includes an NaI(Tl) crystal, a photomultiplier tube (PMT), a PMT base with a pre-amplifier, an internal magnetic/light shield, an aluminium housing and a 14-pin connector.The best resolution achievable for the present detector is about 7.5% for the 662-keV gamma ray from Cs-137 for a 3-in.diameter by 3-in.long NaI crystal (CANBERRA, model: 802).The weak detector pulse enters the preamplifier which has two main functions: pulse shaping and amplitude gain.The amplified pulse is then fed to the multi-channel analyser (MCA), which converts the analogue signal into a digital number through an analogue to digital converter (ADC).The pulse height spectra were recorded with a computerized 2 K MCA plug-in-card.The transmitted spectra were recorded for sufficient time to collect an adequate number of counts under the photo peak to limit the statistical error less than 0.3%.The background counts recorded for the same time were subtracted from each spectrum.To stop the fluorescence X-rays ( E75 keV) of lead from reaching the detector, the lead shield was lined on the inside with brass and aluminium sheets.The stability and reproducibility of the experimental procedure were tested using aluminium as a reference absorber at 662 keV.The experiment was performed at low temperature to avoid any shift of peak.coefficients of concretes.The maximum errors in mass attenuation coefficients were calculated from errors in incident (I 0 ) and transmitted (I) intensities, mass density (ρ) and thickness (t) using the propagation of error formula:

Results and discussion
where t is the sample thickness in centimeters, ΔI 0 , ΔI, Δρ and Δt are the errors in the intensities I 0 , I ,density ρ and thickness t of the glass sample, respectively.Estimated error in experimental measurements was less than 3.80%.It was found that the experimental results are in good agreement with theoretical results within estimated errors.From Table 4, it is clear that mass attenuation coefficient of lead-flyash concretes remains constant with variation of flyash from 0% to 60%.Although density of lead-flyash concretes decreases with increase in flyash, but mass attenuation coefficient do not decreases because it is independent of density of target material.It depends upon the chemical composition of material.Linear attenuation coefficient decreases with increase in flyash content in concretes (Fig. 2).It also decreases with increase in gamma ray energy for all variations of flyash.This trend is due to the fact that with increase in energy, linear attenuation coefficient decreases and more thickness of target material will be required to compensate the decrease in linear attenuation coefficient.
The results of thickness of concrete required to reduce the transmitted intensity to half of its incident intensity i.e. half value layer (HVL) has been measured for lead-flyash concretes to assess their shielding ability.Shielding effectiveness of a sample is inversely related to the value of HVL.With the increase in energy, HVL increases because to reduce intensity of incident gamma radiations to its half value, more thickness of target will be needed.The measured HVL for lead-flyash concretes has been compared with ordinary-flyash concretes with same variation of flyash in place of cement to assess their shielding ability.It is clear from Fig. 3 that HVL for any lead-flyash concretes are lower than its corresponding value for ordinary-flyash concrete with same percentage of flyash content.It means that lead-flyash concretes are better in gamma ray shielding than ordinary-flyash concretes for the different sources of gamma ray used.Also it is evident that HVL for lead-flyash concrete at energy 1332 keV is less than HVL for ordinary-flyash concrete at energy 1173 keV.Although the trend of variation of linear attenuation coefficients with variation in flyash content is same as of half value layer (HVL), but their change in value is not quite clear as there in the values of HVL.
For the prepared concrete specimens, the effective atomic numbers have been determined from the mass attenuation coefficients of lead-flyash concretes and also of their constituent elements.The obtained values of experimental and theoretical values of effective atomic numbers are shown in Table 5.With the increase in flyash content, effective atomic numbers of lead-flyash concretes decreases.The experimental and theoretical values of electron density are shown in Table 6.The electron density is nearly constant for all concrete specimens in the range of 2.85-3.10Â 10 23 electrons per unit gram of material.
The mass attenuation coefficients of all six concretes was also calculated with the help of winXCOM, a computer programme initially developed by Berger and Hubbell and later modified to window version by Gerward et al. (2004).From the results obtained, other interactions parameters were also computed.
The radiation exposure rates at any distance from a particular radionuclide without target material in the path was calculated from the following expression 2 where Γ ¼specific exposure rate constant (R cm 2 /mCi h), A ¼activity in mCi, and d ¼ distance (in cm) from a point source of radioactivity.Table 7 shows the exposure rate (R/h) along with its SI units at the front face of detector i.e. at a distance of 57 cm from source without using target and also in the presence of target in its path (lead-flyash concretes).The exposure rate is constant for the brief exposure period of experiment as half-life of all gamma ray sources is long enough in its comparison.The exposure rate at any distance and at any time can be calculated from the given results.The results of the number of decays per second, or activity from radioactive nuclei 60 Co and 137 Cs, a measure of the amount of radioactivity present in material, was 17.8 Â 10 7 Bq and 343.5 Â 10 7 Bq respectively.

Conclusion
Lead-flyash concretes grow in strength with their age.The free lime is generated as a result of hydration of cement in concrete.The reactive silica present in flyash converts free lime into calcium silicate hydrates, which is insoluble in water and possesses cementitious properties.It leads to further gain of strength at later ages in concrete.
The comparison of gamma radiation shielding properties of lead-flyash concretes with ordinary flyash concretes at different gamma ray energies shows that lead-flyash concretes are more capable than ordinary flyash concretes in shielding gamma rays with same percentage of flyash variation in place of cement.

4. 2 .
Radiation Parameters 4.2.1.Attenuation Coefficient.The elemental composition of the six concretes used in this study is shown in Table 4

Figure 1 :
Figure 1: (a) Compressive strength of ordinary concrete versus age.(b) Compressive strength of flyash concrete versus age.
investigated radiation properties of different types of concretes and good agreement between the calculated and measured values was reported.Singh et al. (2004) and Akkurt et al. (2004) studied building materials as shielding materials for gamma radiations both theoretically as well as practically.Kumar and Reddy (1997) and Yilmaz et al. (2011) studied effective atomic numbers of some concretes.Kharita et al. (2008) and Akkurt et al. (2010) studied shielding characteristics of concretes using barites and natural local materials by evaluating half value layer and tenth value layer.Manohara et al. (2008) computed electron density of different materials above 1 keV.To have desired compressive strength, cement intake is high in concretes, which leads to bad effect on the human health and environment.So besides trying for various admixtures in the preparation of concretes as a gamma shielding material by narrow beam geometry technique, much emphasis has always been on checking of attenuation in concretes incorporating different cement substituents.For preparing concretes, research Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/apradisoApplied Radiation and Isotopes http://dx.doi.org/10.1016/j.apradiso.2014.10.0220969-8043/& Published by Elsevier Ltd. n Corresponding author.E-mail address: sukhpal_pbiuni@rediffmail.com (S.Singh).Applied Radiation and Isotopes 95 (2015) 174-179 Incident and transmitted intensities have been measured for experimentally determining the values of mass attenuation
Ordinary Portland cement (43 grade) was used.The physical properties of cement are given in Table 2.1.Materials.

Table 1 :
Physical properties of Portland cement.

Table 2 :
Sieve analysis of aggregates.

Table 4 :
Elemental analysis of concrete mixtures.

Table 5 :
Results of radiation parameters.
goes on increasing for flyash concretes.The pozzolanic reaction of flyash develops later than cement.
al. (2001) and Atis (2005) conducted studies regarding strength properties of concrete incorporating different percentages of flyash.Singh et al. (2003) studied flyash as a radiation shielding material for gamma rays and it was concluded that it if compacted to high degree, it can be used for shielding purposes.Poon et al. (2000) studied mechanical and radiation properties of concrete prepared with large volumes of low calcium flyash.Singh et al. (2008) concluded that barium-borate-flyash glasses are better radiation shielding materials than ordinary barium-borate glasses.

Table 2
Weight fractions of lead-flyash concretes.

Table 4
Mass attenuation coefficients of lead-flyash concretes.

Table 5
Effective atomic numbers of lead-flyash concretes.

Table 7
Exposure rate of different energies with and without target in path.Energy (keV) Average exposure rate (mR/h) Average exposure rate (mC/kg h)