Radioactive assessments of concrete modified with recycled waste materials

The burgeoning population and urbanization are driving an increase in concrete production worldwide. Preserving the properties of recycled waste materials, which partially replace cement in concrete production, becomes crucial for safe and durable structures. In this investigation, concrete was produced from 5 to 15 wt% cement substitutes with recycled waste materials such as furnace steel slag powder (FSP), calcite powder (CP), and corncob ash (CCA). After 28 days of curing, the compressive strength of the concrete specimens was determined. A thallium-activated Sodium Iodide detector was engaged to analyze the activity concentrations (²²⁶Ra, ²³²Th, and ⁴⁰K) of the concrete specimens and constituents while other radiological hazard parameters were quantified. The results indicated that at 5–15 wt% of FSP, CCA, and CP substitution, the designed compressive strength of 25 MPa was achieved, and the activity concentrations of concrete specimens were reduced relative to the control concrete. The radionuclides in the blended concrete specimens varied from 4.01 ± 0.12 to 13.08 ± 0.12 Bq/kg for ²²⁶Ra, 3.64 ± 0.13 to 9.93 ± 0.08 Bq/kg for ²³²Th, and 550.37 ± 7.92 to 1166.70 ± 11.38 Bq/kg for ⁴⁰K compared to the control specimens with 19.10 ± 0.12, 7.92 ± 0.12, and 1368.51 ± 12.32 Bq/kg, respectively. All activity concentrations of concrete constituents, except ⁴⁰K in granite, were below the allowable thresholds set by international standards. Thus, FSP, CCA, and CP can safely be used at 5–15 wt% replacement with cement for concrete production without posing radioactive hazards.