This paper reports an experimental study on hexavalent chromium leaching from cement samples and cement composites containing silica fume and zeolite additions that were subjected to various leaching agents. The water-soluble Cr(VI) concentrations in cements ranged from 0.2 to 3.2 mg/kg and represented only 1.8% of the total chromium content. The presence of chromium compounds with both chromium oxidation states of III and VI was detected in the cement samples by X-ray photoelectron spectroscopy (XPS). Leaching tests were performed in a Britton-Robinson buffer to simulate natural conditions and showed increased dissolution of Cr(VI) up to 6 mg/kg. The highest amount of leached hexavalent chromium was detected after leaching in HCl. The findings revealed that the leaching of chromium from cements was higher by 55–80% than that from the cement composites. A minimum concentration was observed for all cement samples when studying the relationship between the soluble Cr(VI) and the cement storage time.

The radionuclide activities of ²²⁶Ra, ²³²Th and ⁴⁰K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices) of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg⁻¹, 9.78–26.3 Bq·kg⁻¹ and 156.5–489.4 Bq·kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Ra_eq = 67.87 Bq·kg⁻¹, gamma index I_γ = 0.256, alpha index I_α = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h⁻¹, external hazard index H_ex = 0.182 and internal hazard index H_in was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg⁻¹ for ²²⁶Ra, 13.1–20.5 Bq·kg⁻¹ for ²³²Th and 250.4–494.4 Bq·kg⁻¹ for ⁴⁰K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.