Development of a continuous flow reactor - first study of cement paste degradation

The degradation of Portland Cement has been investigated using a flow-through reactor, new to this field. Evolution of the system has been interpreted from analyses of solution and solid phase and is compared to the degradation scheme known from literature. Motivation for testing the setup performance with cement is to perform radionuclide retention studies. It is believed that the experimental design will permit a new perspective, complementing dynamic batch and classical column experiments. First results presented here initiate suitability tests, so far indicating the setup applicability. The results show that several successive stages of degradation could be discerned and were interpreted to be characterised by: -) the presence of dissolving portlandite and incongruently dissolving C-S-H, -) incongruently dissolving C-S-H when all portlandite has dissolved completely and -) congruently dissolving C-S-H, possibly coexisting with neo-formed C-A-S-H. These different stages can be distinguished by analyses of outflow solutions. Suggestions for radionuclide retention studies are also made