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The reuse of industrial by-products is important for members of numerous industrial sectors. However, though the benefits of reuse are evident from an economical point of view, some compounds in these materials can have a negative effect on users' health.In this study, the radon emanation and exhalation features of red mud were surveyed using heattreatment (100 to 1200°C). As a result of the 1200°C-treated samples, massic radon exhalation capacity reduced from 75 ± 10 mBq kg -1 h -1 to 7 ± 4 mBq kg -1 h -1 , approximately 10% of the initial exhalation rate.To find an explanation for internal structural changes, the porosity features of the heat-treated samples were also investigated. It was found that the cumulative pore volume reduced significantly in less than 100 nm, which can explain the reduced massic exhalation capacity in the high temperature treated range mentioned above.SEM snapshots were taken of the surfaces of the samples as visual evidence for superficial morphological changes. It was found that the surface of the high temperature treated samples had changed, proving the decrement of open pores on the surface.

The main goal of research presented in this paper was the material and radiological characterization of high volume fly ash concrete (HVFAC) in terms of determination of natural radionuclide content and radon emanation and exhalation coefficients. All concrete samples were made with a fly ash content between 50% and 70% of the total amount of cementitious materials from one coal burning power plant in Serbia. Physical (fresh and hardened concrete density) and mechanical properties (compressive strength, splitting tensile strength and modulus of elasticity) of concrete were tested. The radionuclide content ( 226 Ra, 232 Th and 40 K) and radon massic exhalation of HVFAC samples were determined using gamma spectrometry.Determination of massic exhalation rates of HVFAC and its components using radon accumulation chamber techniques combined with a radon monitor was performed. The results show a beneficial effect of pozzolanic activity since the increase in fly ash content resulted in an increase in compressive strength of HVFAC by approximately 20% for the same mass of cement used in the mixtures. On the basis of the obtained radionuclide content of concrete components the I-indexes of different HVFAC samples were calculated and compared with measured values (0.27 -0.32), which were significantly below the recommended 1.0 index value. The prediction was relatively close to the measured values as the ratio between the calculated and measured I-index ranged between 0.89 and 1.14. Collected results of mechanical and radiological properties and performed calculations clearly prove that all 10 designed concretes with a certain type of fly ash are suitable for structural and non-structural applications both from a material and radiological point of view. KeywordsFly ash, Concrete, NORM, I-index, Radon exhalation 1. Introduction BackgroundThe building industry has one of the largest environmental impacts among all human activities:an annual consumption of 10 -11 billion tons of aggregate (Meyer, 2002) and 4.18 billion tons of cement (USGS, 2015). Apart from extremely high resource and energy consumption, cement production is a significant source of CO2 emissions, accounting for approximately 4.4% of global CO2 emissions from industry in 2007(Boden et al., 2010.There are many ideas that have been proposed to make concrete "greener" and more sustainable but they are all based on two principles: reuse and reduce. Concepts based on the "reduce" principle are oriented towards decreasing cement production based on natural materials and result in a reduction in CO2 emissions. With respect to the requirements for concrete as the world's most used man-made material, a lower production of Ordinary Portland cement must be compensated with alternative sources of binders in concrete production. There are several industrial sectors which produce significant amounts of residues such as fly ash (FA), bottom ash, red mud, steel slag, nonferrous slag, etc. which can be used for that purpose (Shi et al., 2006).Millions of tons of FA,...

The Naturally Occurring Radionuclide (Ra-226, Th-232 and K-40) content of building Materials (NORM) contributes to the total radiation dose experienced by humans. In this survey 27 clay and 68 red mud samples were surveyed with gamma spectrometry and screened according to European Basic Safety Standards (BSS) Iindex. It was found that average I-index of clays was 0.6 (0.4-0.8) less than the I-index of 1, which makes them suitable for building material production. The average I-index of red mud 2.3 (1.3-3.0). The maximal mixing ratio of red mud was calculated, varied between 12-39 %, with 23 % average.

Highlights  Datamining was used for the construction of the NORM4Building database  Systematic radiological evaluation of by-products for use in concrete  Radiological evaluation of cement, concrete, ceramics and (phospo)gypsum  The datamining approach enables the construction of an updated detailed database

h i g h l i g h t s Manual datamining was used to gather separately reported sample information. 431 by-products and 1095 construction materials were collected from 48 countries. Ra-226, Th-232 content were 2.00 and 2.11 times higher in the case of by-products. Ra equivalent concentration was 1.86 times higher in the case of by-products. I-index >1.0 in the event of 17% of construction materials; 58% of by-products.

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