Radiological safety assessment of blended cement concrete

Maintaining the qualities of supplementary cementitious materials (SCMs) used as Portland limestone cement (PLC) replacement in concrete manufacturing for the safety and durability of buildings is essential. This study produces concrete from cement modified with SCMs such as seashell powder (SSP), shea nutshell ash (SNA), and aluminium dross (AD) at 0-15 wt. % substitution with 0 wt. % SCMs substitution serving as control concrete. Mix proportions were designed using C25 MPa concrete grade, prepared, and tested for compressive strength after 28 curing age. The activity concentrations of radionuclides (ACRs) in raw materials and concrete samples were determined using a NaI (Tl) detector coupled with a Canberra MP2-2U as the detecting device for gamma-ray spectrometry. The results showed that all concrete samples incorporated with SCMs attained the design compressive strength, and their ACRs (226Ra, 232Th, and 40 K) were reduced at 5-15 wt. % of SSP, SNA, and AD substitutions. The mean values of 226Ra, 232Th, and 40 K in the raw materials (concrete constituents) were 28.06 +/- 0.48, 17.91 +/- 0.31, and 1007.75 +/- 10.27 Bq kg-1. The mean values of 226Ra, 232Th, and 40 K in the concrete samples were 16.29 +/- 0.17, 5.47 +/- 0.12, and 1145.65 +/- 10.92 Bq kg-1 compared to control concrete with mean values of 27.29 +/- 0.73, 7.92 +/- 0.12, and 1368.51 +/- 12.32 Bq kg-1. All radionuclides were below the standards' recommendations, except for 40 K in granite. Therefore, SSP, SNA, and AD can be utilized safely at 5-15 wt. % of PLC substitution for concrete manufacturing without endangering prospective users with radioactivity.