Development of a sample preparation procedure for Sr isotope analysis of Portland cements

Anera Kazlagić,Francesco F Russo,Jochen Vogl,Patrick Sturm,Dietmar Stephan,Gregor J G Gluth

doi:10.1007/s00216-021-03821-7

Abstract

The 87Sr/86Sr isotope ratio can, in principle, be used for provenancing of cement. However, while commercial cements consist of multiple components, no detailed investigation into their individual 87Sr/86Sr isotope ratios or their influence on the integral 87Sr/86Sr isotope ratio of the resulting cement was conducted previously. Therefore, the present study aimed at determining and comparing the conventional 87Sr/86Sr isotope ratios of a diverse set of Portland cements and their corresponding Portland clinkers, the major component of these cements. Two approaches to remove the additives from the cements, i.e. to measure the conventional 87Sr/86Sr isotopic fingerprint of the clinker only, were tested, namely, treatment with a potassium hydroxide/sucrose solution and sieving on a 11-µm sieve. Dissolution in concentrated hydrochloric acid/nitric acid and in diluted nitric acid was employed to determine the 87Sr/86Sr isotope ratios of the cements and the individual clinkers. The aim was to find the most appropriate sample preparation procedure for cement provenancing, and the selection was realised by comparing the 87Sr/86Sr isotope ratios of differently treated cements with those of the corresponding clinkers. None of the methods to separate the clinkers from the cements proved to be satisfactory. However, it was found that the 87Sr/86Sr isotope ratios of clinker and cement generally corresponded, meaning that the latter can be used as a proxy for the clinker 87Sr/86Sr isotope ratio. Finally, the concentrated hydrochloric acid/nitric acid dissolution method was found to be the most suitable sample preparation method for the cements; it is thus recommended for 87Sr/86Sr isotope analyses for cement provenancing.Graphical abstract

Highlights

Concrete is the most important artificial material in the world in terms of produced mass, and it is considered to be the basis for our built environment [1]
The present results clearly show that the applied sieving procedure did not separate additives from clinker in the cement
A likely explanation is that the fine calcium sulfate particles stuck to the clinker particles during sieving due to physical bonding

Summary

Introduction

Concrete is the most important artificial material in the world in terms of produced mass, and it is considered to be the basis for our built environment [1]. Since the properties of concretes are dominated by their key compound, cement [2], devising a way to determine its origin, known as provenancing, is of great importance. To determine the origin of cement, it is important to understand its composition and production process. As specified in European Standard EN 197–1, Portland cement (CEM I) contains at least 95 wt.% of Portland clinker (disregarding the calcium sulfate addition). Natural gypsum and/or anhydrite, industrially processed chemical gypsum, or flue gas desulfurisation (FDG) gypsum is employed [10]. Each of these materials contains strontium, an element whose isotopes provide information on the geographical origin, and, is highly valuable for provenance studies

Methods

Results

Discussion

Conclusion