Development of an analysis concept for the quantification of cement, its main constituents as well as additives in hardened concrete

Knowledge of concrete composition is very important in terms of revitalisation and conversion of buildings with cement-bound building materials, as well as in the case of defects and damage. Often, the corresponding documentation to accompany the structure is no longer available. For this reason, precise subsequent determination of the cement content, cement type, additive content and aggregate in the hardened concrete is useful and necessary. However, this is not possible or just possible to an insufficient extent, with the analytical methods that are currently available.

As part of the project, methods were developed that allow the cement content, cement type and additive content in hardened concrete to be reliably determined. The project essentially took two different approaches. On the one hand, wet chemical methods based on DIN 52170 and CEN/TR 196-4 were to be optimised in such a way that as many parameters as possible can be determined as accurately as possible. On the other hand, image analysis-based approaches were to be used, whereby images can be gained through element mappings with a micro XRF and an SEM (EDX). The image analysis-based methods was also optimised in terms of the effort involved in preparation, the number of images to be taken and the evaluation method. The methods identified should then be validated using various samples of concrete. The influences of the cement and additive content, age of the concrete, various cement types and aggregates on the applicability and precision of the methods were investigated.