Concrete drill cores

In civil engineering the chemical analysis of concrete is an important task in terms of damage assessment. The standard procedure for the determination of chloride in concrete cores or drill cores is the potentiometric titration (wet chemistry). This method is a time- and cost consuming and it is not possible to consider the heterogeneity of the concrete caused by the aggregates. The chloride concentration is determined regarding to the total mass. A transfer to the cement content is only possibly due to estimated correction factors.

The Laser-Induced Breakdown Spectroscopy (LIBS) offers a great advantage compared to the standard procedure as the heterogeneity can be considered by a spatial resolved measurement (2D element maps). Due to a 3D-translation stage (X-Y-Z) the element distribution of different elements can be resolved within on measurement as LIBS is capable to detect multiple elements at the same time (Cl, Na, K, S, C etc.). By applying multivariate analysis, the non-relevant aggregates can be excluded from the data set and the chloride concentration on can be referred to the cement matrix only. LIBS need only an optical access to the sample surface. This is achieved by cutting the concrete core into two pieces. At the moment, the LIBS method is on the way towards standardization to provide crucial information and regulations for a safe handling.

The procedure will be describe in detail in the updated brochure of the DAfStb "Grünen Heft" 422.