A SEM-EDX Study of the Processes at the Concrete/Compacted Bentonite Interface

A 4.7 years column experiment was performed to study the interaction between concrete and compacted FEBEX bentonite (1.6 g/cm³; dry density). The experiment was dismantled under the development of the PEBS project. A SEM-EDX study was performed along a polished section of the concrete-bentonite column. The calcium front exceeded the first two mm of interface confirming the alkaline diffusion. Calcite, mainly in the bentonite, and calcium silicates (aluminates) hydrates (C-S-A-H) type materials were identified in secondary electrons mode. The SEM-EDX technique provides valuable data on spatial development of reaction fronts produced in bentonite, but XRD and FTIR are also fundamental tools to confirm spatial reaction front results, and unavoidable to update the nature of mineral phases formed. (authors)