A new technique to reduce the radioactivity of fly ash utilized in the construction industry Gökhan Baykal a , Altug Saygılı b,⇑ a Civil Engineering Department, Bogazici University, 34342 Istanbul, Turkey b Civil Engineering Department, Mugla University, 48000 Mugla, Turkey article info Article history: Received 20 July 2010 Received in revised form 21 December 2010 Accepted 4 January 2011 Available online 18 January 2011 Keywords: Fly ash Radioactivity Utilization By products Embankment construction abstract High volume utilization of industrial wastes and by products is the solution for high disposal costs. Accept- able radioactivity levels in addition to other environmental factors is a key factor for safe utilization of wastes and byproducts of coal burning power plants. In general the radioactivity levels of most fly ashes are similar to natural materials. For higher radioactivity fly ash the radioactivity values must be reduced to acceptable limits. This can be done by mixing the fly ash with less radioactive natural materials. In this study a new technique involving the use of snow as an additive to the compaction water of fly ash is presented. Fly ash at optimum water content, and fly ash with additional 10% by weight snow are compacted, hermetically sealed to allow for equilibrium of 226 Ra and 232 Th with their decay products and cured for 28 days at the curing room. Radioisotope activity analysis are conducted with a gamma analyst integrated gamma spectrometer. The activities of 235 U, 226 Ra, 238 U, and 232 Th of the fly ash and snow-added fly ash samples compacted at optimum moisture content are determined. The control samples revealed radioactivity values above UNIPEDE maximum allowable limits. Addition of snow caused a decrease of 31–42% in the radioisotope activity levels to that of control samples in Bq kg À1 . The decrease in radioactivity is linked to increased void ratio after melting of ice, increased densification of matrix around the pores due to higher level of cementitious mineral formation. The decrease in the radioisotope activity levels will allow utilization of fly ash in highway embankment construction where large surface area exposure and large volume usage makes it more critical for human health. Another advantage of the developed technology is the reduction of transportation costs by more than ten per cent by using less material for construction. Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. 1. Introduction Due to the developing industry and growing population, electricity consumption and therefore demand for electricity generation has increased. This increasing trend in the electricity requirements leads construction of new thermal power plants. Coal-fired thermal power plants are used widely all over the world. In Turkey low calorie lignite which is not appropriate for dwelling use is extensively used for electricity production. Moreover, envi- ronmental problems of fly ash such as wide area requirements for disposal, pollution of air, soil and water associated with ponds of ashes stored near the power plants have become preventing items for coal-fired power plants. As environmental consciousness in- creases throughout the world, utilization of fly ash like other waste materials have become important and provide economic advanta- ges such as providing cheap mineral resource for construction activities and savings in the costs to construct by-product storage facilities. In the United States 131 million tons of fly ash is produced annually by 460 coal-fired power plants. An industry survey esti- mated that 43% of this ash is re-used [1]. In Turkey 17 million tons of fly ash is produced with less than 1 million ton utilized. Fly ash is utilized in huge quantities in highway applications. The use of materials containing natural radioactive nuclides (such as coal fly ash) in the construction industry and building materials is controlled by the legal agencies to examine the radioactive dose levels originated from the product. Utilizing fly ash with an allow- able level of radioactivity in highway embankment construction activities is an efficient way of utilization. Large quantities of fly ash exceeding the allowable radioactivity limits can be beneficially used in geotechnical, geoenvironmental and highway applications with the developed technique presented in this paper. Assessment of the radiation exposure from coal burning is critically dependent on the concentration of radioactive elements in coal and in the fly ash that remains after combustion. Data for uranium and thorium content in coal is available from the US 0016-2361/$ - see front matter Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2011.01.006 ⇑ Corresponding author. Tel.: +90 252 2111942; fax: +90 252 2111911. E-mail addresses: saygili@mu.edu.tr, altugsaygili@yahoo.com (A. Saygılı). Fuel 90 (2011) 1612–1617 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel