Radiological characteristics of Self-Compacting Concretes incorporating fly ash, silica fume, and slag

This article presents the results of a comprehensive study investigating the hypothesis that higher concentrations of natural radionuclides, that are harmful to human health, may be present in Self-Compacting Concretes (SCCs) due to its higher powder material content compared to conventional concretes. The fresh (slump-flow, T-500 time, V-funnel) concrete and compressive strength of SCCs prepared by replacing Portland cement with fly ash (FA), silica fume (SF), and ground granulated blast furnace slag (GGBFS) in the respective range of 5%, 12.5%, and 20% were determined. The radionuclide activity concentration of all solid concrete components and SCCs were determined using the gamma spectrometry method. Radioactivity analyses including the calculation of the activity concentration index and annual effective dose equivalents were also performed. The findings showed that the specimens with the highest average compressive strength at the end of 120th day were, respectively, SF (54.2 MPa), FA (52.2 MPa) and GGBFS (46.1 MPa) added to the SCC. The obtained concentration of the Radium-226 value (41.1) of 20% UK with added SCC was 1.8 times higher than the control concrete (22.7) and 2 times higher than 20% SF added SCC (19.7). The highest Radium equivalent activity (Ra-eq) values were FA20 (89.52), GGBFS20 (72.05), control concrete (70.86) and SF20 (68.01). It was determined that the FA selected for the study exceeded the limit specified for structural material (3.38 > 1) and fell in the radiologically hazardous class. It has been proven that SF can be used as a radioactivity reducing material of concretes. The results revealed that the research hypothesis was confirmed in terms of FA.

Automated summary

This study investigated the hypothesis that higher concentrations of natural radionuclides, harmful to human health, may be present in self-compacting concretes (SCCs) due to its higher powder material content compared to conventional concretes. The findings showed that adding fly ash, silica fume, and ground granulated blast furnace slag can increase the compressive strength of SCCs. Fly ash exceeded the limit for structural material, while silica fume proved to be an effective material in reducing concrete radioactivity.