Radon exhalation of cementitious materials made with coal fly ash: Part 1--scientific background and testing of the cement and fly ash emanation.

Increased interest in measuring radionuclides and radon concentrations in fly ash, cement and other components of building products is due to the concern of health hazards of naturally occurring radioactive materials (NORM). The current work focuses on studying the influence of fly ash (FA) on radon-exhalation rate (radon flux) from cementitious materials. The tests were carried out on cement paste specimens with different FA contents. The first part of the paper presents the scientific background and describes the experiments, which we designed for testing the radon emanation of the raw materials used in the preparation of the cement-FA pastes. It is found that despite the higher (226)Ra content in FA (more than 3 times, compared with Portland cement) the radon emanation is significantly lower in FA (7.65% for cement vs. 0.52% only for FA).