Radiological evaluation of industrial residues for construction purposes correlated with their chemical properties

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis study characterises the naturally occurring radionuclide (NOR) contents of a suite of secondary raw materials or industrial residues that are normally disposed of in landfills or lagoons but now are increasingly used in green concretes. This includes ashes from a variety of industrial processes and red mud from aluminium production, as well as air pollution control residue and cement kiln dust. The chemical composition of the samples was determined with X-ray fluorescence spectroscopy (XRF). The Ra-226, Th-232 and K-40 activity concentrations were obtained by gamma spectrometry, and the results were compared with recently published NOR databases. The correlation between the NOR contents and the main chemical composition was investigated. The radioactive equilibrium in the U-238 chain was studied based on the determination of progeny isotopes. The most commonly used calculation methods (activity concentration index and radium equivalent concentration) were applied to classify the samples. The radon exhalation rate of the samples was measured, and the radon emanation coefficient was calculated. Significant correlation was found between the NORs and certain chemical components. The massic exhalation demonstrated a broad range, and it was found that the emanation coefficients were significantly lower in the case of the residues generated as a result of high-temperature combustion processes. The results showed a weak correlation between the Ra-226 concentration and the radon exhalation. This emphasises that managing the Ra-226 content of recycled material by itself is not sufficient to control the radon exhalation of recycled materials used in building products. The investigated parameters and their correlation behaviour could be used to source apportion materials found during the process of landfill mining and recovery of material for recycling.European Union Horizon 202

Radiological evaluation of by-products used in construction and alternative applications; Part I. - preparation of natural radioactivity database

To get an insight into the radiological features of potentially reusable by-products in the construction industry a review of the reported scientific data is necessary. This study is based on the continuously growing database of the By-BM (H2020-MSCA-IF-2015) project (By-products for Building Materials). Selection criteria were defined for manual data mining in such a way to avoid the collection of too heterogeneous datasets. Currently, the By-BM database contains individual data of about 431 by-products and 1095 construction and raw materials. The By-BM database only consists out of measurement information on individual samples and not out of processed data that only gives a rough summary (such as only a range or average) of experimental results. As a consequence of the statistical analysis of the data, it was found that in the case of the construction materials the natural isotope content had a wider distribution than the by-products. However, the average of the Ra-226, Th-232 and K-40 contents of reported by-products were 2.00, 2.11 and 0.48, while the median was found 1.97, 1.24 and 0.53 times higher than the construction materials, respectively. The calculated Radium equivalent concertation was greater than the accepted value for residential properties of 370 Bq/kg in the event of 10.3% of total construction materials and 42.4% of by-products, while the I-indexes were above 1.0 index value with 17.3% and 58.2%, respectively. From the obtained data, it can be concluded that the reuse of industrial by-products in construction materials for residential purposes, without due diligence, can pose elevated risks to residents as a result of their high-volume usage. (C) 2017 Elsevier Ltd. All rights reserved.The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 701932. R. Doherty's time was also supported by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 643087. The authors would also like to acknowledge networking support by the COST Action TU1301. www.norm4building.org.by-products; building materials; Reuse; natural radiation; database; I-index; mixin

Fluorescence lifetimes and emission patterns probe the 3D orientation of the emitting chromophore in a multichromophoric system

In this Communication, we report on the fluorescence behavior of an individual first generation multichromophoric dendrimer. The fact that each of the chromophores in time acts as a fluorescent trap is demonstrated by directly probing the dipole orientation of the emitting chromophore by means of defocused wide-field imaging and comparing experimental and calculated emission patterns. It is shown that in such cases the electromagnetic boundary condition effect results in discrete changes in the fluorescence lifetime as a function of time for individual dendrimers

The effect of high dose rate gamma irradiation on the curing of CaO-FexOy-SiO2 slag based inorganic polymers: Mechanical and microstructural analysis

In search for alternative cementitious materials for radioactive waste encapsulation, geopolymers and inorganic polymers (IPs) have received wide attention. Moreover, Fe-rich IPs offer an interesting alternative to high density concretes for use in radiation shielding applications. Materials can however be altered when subjected to ionizing radiation, creating the necessity to evaluate the material’s behaviour under irradiation conditions. In this study the effect of high dose rate (8.85 kGy/h) gamma irradiation is investigated on CaO-FexOy-SiO2 slag-based IPs. Samples with different curing times (1 h, 24 h and 28 days) prior to the irradiation were irradiated to a dose of 200 kGy using a60Co source. The effect of gamma radiation is observed to be highly dependent on the curing time prior to irradiation. 28 days cured samples are found to be resistant to the irradiation for the dose (rate) and properties tested without any significant change in strength, indentation characteristics, porosity and Fe3+ content. The IPs studied show a different behaviour when irradiated immediately after casting or after 24 h of curing. It is therefore thought that the mechanism behind the effect of irradiation is different for the non-hardened samples compared to hardened samples. For the 1 h cured samples prior to irradiation multiple effects were observed: an increase of the compressive strength by a factor 2.20, a decrease in hardness of the binder by a factor of 0.73, a lower Young’s-modulus of the binder by a factor of 0.67, a decrease of creep in time for the binder by a factor of 0.72, a decrease in porosity by a factor of 0.92 and an increase of the Fe3+/ΣFe ratio by a factor of 1.95.JRC.G.I.3-Nuclear Fuel Safet

Development of alkali activated cements and concrete mixture design with high volumes of red mud

Dedicated cement compositions were formulated to enable the incorporation of large volume fractions of red mud in alkali activated cements, taking into account the role of the aluminosilicate phase in the processes of hydration and hardening. High volume red mud alkali activated cements were synthesized using a proper combination of red mud, low basic aluminosilicate compounds with a glass phase (blast-furnace slag) and additives selected from high-basic Ca-containing cements with a crystalline structure (Portland cement). Compressive strength of the cements under study is 30-60 MPa (tested in mortar). The microstructure of the hardened cement paste and the role of red mud in the structure formation process were investigated. In addition to the use of red mud in cement, its use as an aggregate in concrete was studied to enable the use of larger quantities in the final concrete. In concrete road bases, the use of red mud can reach even 90 % by mass. Since enhanced concentrations of naturally occurring radionuclides can be present in red mud this aspect was investigated to make sure that these materials are safe to use from a radiological point of view.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Adsorption of cesium on different types of activated carbon

The optimal conditions to remove radiocesium from water by adsorption on activated carbon (AC) were investigated. Two commercial ACs were compared to ACs prepared by steam activation of brewers’ spent grain. The influence of pH and loading AC with Prussian Blue were studied. 134Cs, measured by gamma-ray spectroscopy, served as a tracer for the Cs concentration. Column experiments showed that a neutral to acidic pH enhanced adsorption compared to high pH. Norit GAC 1240 had the highest adsorption capacity, 8.5 µg Cs g-1 AC for a column filtration. Sequential columns of Norit GAC 1240 removed 28.1 ± 2.8 % of Cs per column.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Feasibility of incorporating phosphogypsum in ettringite-based binder from ladle slag

Abstract Aiming to utilize phosphogypsum (PG) as a construction material, this study investigated the potential use of PG as a calcium sulfate source for the production of an ettringite-based binder (LSG). Six compositions with different percentages and PG’s of different origin were hydrated with ladle slag (LS) to form LSG. The hydration, mineralogy and compressive strength of all mixtures were investigated and compared with a reference LSG made of pure synthetic gypsum. The minor impurities in PG, the different particle size distribution as well as the mineralogy induced distinguishable effects on the heat of hydration, phase assemblage and morphology. The results showed that the use of side-stream PG instead of pure gypsum results in superior properties with a 60% increase in compressive strength. This investigation shows high potential to produce a completely by-product-based LSG by combining different sources of industrial side-streams with minimal chemical and energy use