PhD Thesis

Purpose: This study was carried out in order to investigate the hypothesis that radon gas emanation, which is harmful to human health, may occur more in Self-Compacting Concrete (SCC), which has a higher amount of powder material compared to conventional concretes.
Method: The fresh concrete properties of the specimens with 5%-12.5%-20% fly ash (FA), silica fume (SD), ground granulated blast furnace slag (GGBFS) rates were determined by unit weight, slump-flow, T500 time and V-funnel tests. Uniaxial compressive strength, capillary water absorption and rapid chloride ion permeability tests were performed as hardened concrete tests, and the pore-size distrubition of the samples were examined with the BET technique. Radon activity concentrations of concretes with dimensions of 150x150x150 mm placed in closed glass moulds were measured by passive method at the end of 7-14-21-28-56-90 and 120 days using CR-39 nuclear trace detectors. Radioactivity analysis on solid concrete constituents and concretes were carried out by gamma-ray spectrometer method. Measuring radon gas emanation from concretes placed in closed glass environments by passive method is a unique method.
Findings: Radon activity concentrations of SCCs increased significantly with the increase of FA and decreased dramatically with the increase of SF. While 5% GGBFS decreased the radon gas emanation, the emanation increased by 12.5% and 20% GGBFS. The specimens with the highest average compressive strength at the end of 120th day were, respectively, SF, FA and GGBFS added SCC. The lowest capillary water absorption coefficient and chloride permeability value were observed in SF added SCCs, as well as in radioactivity concentrations determined by gamma spectrometer analysis.
Results: It has been determined that SCCs containing 12.5% and 20% FA emit radon gas above the nationally and internationally determined levels. However, SF has reduced the radon gas emanation of the concretes. The use of GGBFS in concrete requires sensitivity in terms of radioactivity. It has been determined that radon gas emanation is related to the permeability of concrete. Concretes with low permeability will also have less radon emanation, but this result may not be valid for the concretes containing components with high radioactivity such as FA. The results showed that the research hypothesis was correct depending on type of mineral additive.