Development of chemical-physical treatment of cement paste for reduction of dismantled radioactive concrete volume

Abstract To reduce the amount of radioactive concrete produced during the dismantling of nuclear power plants, it is essential to remove cement paste attached to aggregates. In this study, the effectiveness of a chemical and physical treatment for cement paste removal was evaluated. Cement-paste specimens having similar size to fine aggregate were treated in a sulfuric acid solution with ultrasonication. The weight loss of the specimens was measured to quantify the degree of decomposition of the cement paste. Scanning electron microscopy, surface hardness test, and inductively coupled plasma analysis were performed to identify the effect of acid treatment on the cement-paste specimens. The results indicated that the cement paste removal is associated with progressive degradation of near-surface layer, and the process can be accurately controlled as a function of water-cement ratio and specimen dimension. The findings are expected to be of great use to disposal of radioactive concrete.