Data on natural radionuclide's activity concentration of cement-based materials

Cement based materials may contain varying levels of radionuclides, mainly 226Ra (from the 238U series), 232Th and 40K, which are used to determine the Activity Concentration Index ("ACI"). According to the European directive Euratom 2013/59 in these materials, the “ACI” must be < 1 to be suitable for their use in construction. In this paper, data on the activity concentration of natural radionuclides in cement-based materials (i.e. cements, additions, pigments and aggregates) as well as their chemical composition are presented. Radioactivity measurements have been determined by using gamma spectroscopy the chemical compositions have been determined by X-Ray Fluorescence. Data for cements measured shown that white cements present a lower concentration of activity than conventional CEM I. In addition, the CAC (Calcium aluminate cements) present high activity concentration in the 232Th series. Regarding additions, FA (Fly Ash) are those that present the highest concentration of activity in the 238U and 232Th series, while olive biomass ashes are those supplementary cementitious materials that show the highest concentration of activity for 40K. Some pigments used in mortar and concrete technology were also characterized. Granitic and volcanic rocks, potentially used as aggregates present much higher activity concentration than the siliceous aggregate.


a b s t r a c t
Cement based materials may contain varying levels of radionuclides, mainly 226 Ra (from the 238 U series), 232 Th and 40 K, which are used to determine the Activity Concentration Index ("ACI"). According to the European directive Euratom 2013/59 in these materials, the "ACI" must be < 1 to be suitable for their use in construction. In this paper, data on the activity concentration of natural radionuclides in cementbased materials (i.e. cements, additions, pigments and aggregates) as well as their chemical composition are presented. Radioactivity measurements have been determined by using gamma spectroscopy the chemical compositions have been determined by X-Ray Fluorescence. Data for cements measured shown that white cements present a lower concentration of activity than conventional CEM I. In addition, the CAC (Calcium aluminate cements) present high activity concentration in the 232 Th series. Regarding additions, FA (Fly Ash) are those that present the highest concentration of activity in the 238 U and 232 Th series, while olive biomass ashes are those supplementary cementitious materials that show the highest concentration of activity for 40 K. Some pigments used in mortar and concrete technology were also characterized.
Granitic and volcanic rocks, potentially used as aggregates present much higher activity concentration than the siliceous aggregate.
© 2020 Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Table   Subject Physics Specific subject area Radioactivity and Radiological hazards in cement based materials Type of data Tables How data were acquired

Specifications
The chemical oxide compositions of the materials were determined on S8 Tiger Bruker X-ray fluorescence (XRF) spectrometer. Loss on ignition was also calculated as per European standard EN196-2:2014 [1] Radiological measurements of the samples were carried out by means of gamma ray spectrometry using a system with two high purity germanium detectors one of them is coaxial (Type p), and the other are BEGe (Broad Energy Germanium detector). Data format Raw Parameters for data collection For FRX measurements, the samples were dried and subsequently ground to ensure a particle size under 63 microns. For radiological measurements of the samples, and in order to ensure secular equilibrium between 226 Ra and 232 Th and their progenies, a plastic cylindrical beaker containers with 75.4 mm of diameter and 31 mm height were used. They were completely filled with each sample, hermetically sealed to avoid 222 Rn losses and let stand for at least 25 days before their measurement. In all cases samples were measured by duplicate.

Description of data collection
The determination of chemical composition of materials by XRF was carried out in pellets or fuse beads. The radionuclides determined in this study were those belonging to the natural radioactive series of uranium, actinium and thorium along with 40 K. The gamma emitters determined in the uranium series were: 234 Th (63 keV), 214 Pb (351 keV), 214 Bi (609, 1120 and 1765 keV), 226 Ra (186 keV eliminating interference from 235 U), 210 Pb (46.5 keV). In the actinium series the activity of 235 U (144 and 163 keV) was determined. For the thorium series the gamma emitters analyzed were: 228 Ac (911 keV), 212 Pb (238 keV) and 208 Tl (583 keV). The activity concentration of 40 K was determined by its characteristic photopeak at 1460 keV. The efficiency calibration of the gamma-ray detectors was computed by using the mathematical code LabSOCS (InSitu Object Calibration Software). The samples were measured for 80,0 0 0 s to minimize the measurement uncertainty and achieve the required detection limits. The spectra were analysed using an Excel spreadsheet and Genie 20 0 0 software. Samples were measured in duplicate, except in cases where not enough sample was available.

Data source location
The samples are from different sources, mainly from Spain and other European countries. The samples were collected by both the IETcc-CSIC and the UPCT. All the samples were registered and centralized in the IETcc-CSIC where they were chemically characterized. An aliquot of the samples was sent to CIEMAT for the determination of the gamma emitters by means of high resolution gamma spectrometry (HPGe).

Data accessibility
With the article

Value of the Data
• The data presented herein can be used as an on-line database of the natural radioactivity of cement-based materials • The data can be used for radiological studies, as well as for dose rate calculations and the Activity Concentration Index of each of the cement based materials. • The results can be the basis for the calculation of the activity concentration or excess effective dose rates described in the European Union Directive 2013/59 [2] for final cement based materials.

Chemical composition of cement based materials
This section presents the chemical composition of all materials along with their loss on ignition. A brief description of the materials accompanies these data.

Cements
Chemical composition of 16 different cements (Portland and other types of cements) is shown in Table 1 . Table 2

Pigments used in mortar and concrete technology
Chemical composition of seven mineral pigments used in building materials is shown in Table 3 .

Aggregates used in mortar and concretes preparation
Finally, six aggregates with particle size between 0-2 mm (one siliceous-A1, three granitic ones A2, A3, A4 and two volcanic ones A5 and A6) used in the preparation of mortars and concretes have been chemically characterised. Results are shown in Table 4 .

Activity concentrations of series 238 U, 235 U, 232 Th and 40 K in cement based materials
The activity concentrations of 238 U, 235 U and 232 Th series as well as and 40 K given in Bq kg −1 in all measured cement based materials are shown below. The uncertainties of the activity concentrations shown in Tables 5 , 6 , 7 and 8 were calculated from the measurement uncertainties (peak area and counting efficiency). The uncertainty associated with the weight of the samples was considered negligible.

Cements
Activity concentrations of 238 U, 235 U and 232 Th series, and 40 K in commercial cements are shown in Table 5 .  Table 6 .

Pigments used in mortar and concrete technology
Activity concentrations of 238 U, 235 U and 232 Th series and 40 K in seven different pigments are shown in Table 7 .

Aggregates used in mortar and concretes preparation
Activity concentrations of 238 U, 235 U and 232 Th series and 40 K for aggregates are shown in Table 8 .

Materials
In this work, a total of 56 samples of components used in cement-based materials have been studied.
Commercial Cements : 16 cements with different chemical and mineralogical composition.   Uncertainties are quoted for a coverage factor k = 2 and are due to measurement uncertainties.  Uncertainties are quoted for a coverage factor k = 2 and are due to measurement uncertainties. Uncertainties are quoted for a coverage factor k = 2 and are due to measurement uncertainties. Uncertainties are quoted for a coverage factor k = 2 and are due to measurement uncertainties.
b Slags: Three vitreous blast furnace slags with different origins (samples S1-S3) and two steel slags (samples S4 and S5). Slags are by-products of iron and steel-making production. c One silica fume (sample SF1) which is a by-product originated in the reduction of quartz with coal, in electric arc furnaces for the production of silicon and ferrosilicon. d One waste glass (sample WG1 ) from urban glass recycling waste. e One limestone (sample L1) f One red mud (sample RM1) that is a solid waste with high iron content, generated in the industrial process to produce alumina from bauxite. g Two samples of metacaolin (sample MK1 and MK2) resulting from the calcination of kaolinitic clays. h Three pozzolans, with different origin and chemical composition (samples PZ1-PZ3) i Two olive biomass samples prepared from the mixture of various biomass bottom ashes (sample OBBAM1) or biomass fly ashes (OBFAM1).
Pigments: Seven pigments (samples P1-P7) commonly used in construction, with different colour and chemical composition. One of them (P6) has a high organic matter content.
Aggregates: Six aggregates with maximum particle size of 2 mm.

Chemical characterization
The chemical characterization of all the materials was determined on a S8 Tiger Bruker Xray fluorescence (XRF) spectrometer. Loss on ignition calculated as per UNE-EN196-2:2014 [1] , was also determined. All samples were dried in an oven at 105 °C for 24 h and then, they were milled to ensure a particle size below 63 microns. The oxide composition of the samples, determined by XRF, was carried out on pressed pellets. For this, 2 g of sample were used with 0.2 g of Hoechst wax C on a boric acid support, in an aluminum capsule. For the preparation of fuse beads, 1 g of sample was mixed with 10 g of melting agent (66% Lithium Tetraborate/34% Lithium Metaborate) and LiBr stripper.

Gamma spectroscopy analysis
Radiological measurements of the samples were performed by gamma spectrometry with a counting time of 80,0 0 0 s, using three High-purity Germanium detectors (one of them is coaxial Type p, and the others are BEGe Type -Broad Energy Germanium detectors).
The detectors have an active surface from 26 to 38 cm 2 and 2 keV resolution for 60 Co and intrinsic efficiencies from 30% to 100%. They are protected with 15 cm iron shield. Main characteristics of both types of Ge detectors are shown in Table 9 .
The gamma detectors are connected to two electronic chains consisting of: two amplifiers, two Analog-to-Digital Converters (ADCs), 2 High Voltage Power Supplies and 2 AIM modules all from Canberra Industries. The AIMs modules have the function of communicating the electronic chain with the PC allowing it to: (1) control the parameters of the detector and electronic chain and (2) acquire the spectra. Once the spectra were acquired they were analysed with Genie 20 0 0 software [6] and a MS Excel spreadsheet [7] . The efficiency as a function of energy was computed by using the mathematical code based on Monte Carlo LabSOCs. The parameters required for this calibration were (1) dimensions and composition of the detector components, (2) dimensions of the sample container and (3) chemical composition and density of the sample matrix [8] .
All samples were measured in specific polypropylene sample container (cylinders 75.4 mm of diameter, 31 mm height) sealed to avoid 222 Rn loses. Each container was totally filled with the sample and the measurements were carried out after 21 days to ensure secular equilibrium between radionuclides and their progeny [9][10][11][12] . The samples were measured in duplicate, except in cases where a sufficient quantity of sample was not available. Radionuclides occurring in natural decay chains headed by 238 U ( 226 Ra), 232 Th and 40 K were determined in the samples. 238 U serie measurements were based on the detection of emissions of their daughter nuclides, 234 Th (63 keV), 226 Ra (186.1 keV), 214 Pb (351 keV) and 214 Bi (609, 1120 and 1765 keV). 232 Th determination was determined on emissions of their daughter nuclides, 228 Ac (911 and 969 keV), 212 Pb (238 keV) and 208 Tl (583 keV) respectively, since their own gamma emitting lines are not of sufficient intense ( 232 Th at 63.8 keV) or present significant interferences with other naturally occurring radionuclides. 235 U (144 and 163 KeV) and 40 K (1460.8 keV) were directly measured by their emissions lines.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have, or could be perceived to have, influenced the work reported in this article.