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

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

Characterisation of Conventional 87Sr/86Sr Isotope Ratios in Cement, Limestone and Slate Reference Materials Based on an Interlaboratory Comparison Study

“…In general, the cements were produced from a carbonate (e.g., limestone) and a silicate (e.g., clay) component with various additive materials (e.g., gypsum, anhydrite, flue gas desulfurisation gypsum, limestone) (Kazlagić et al . 2022). Marl contains both the carbonate and the silicate component and is commonly used when marl deposits occur close to the cement production sites.…”

“…2021, Kazlagić et al . 2022), and for possible technological procedures during renovation of historical objects.…”

“…Reports of reference values for 87 Sr/ 86 Sr isotope ratios in geological materials are limited to a handful of publications, mostly focused on 87 Sr/ 86 Sr isotope characterisation of silicate rock reference materials (Raczek et al 2003, Balcaen et al 2005, Weis et al 2005, Weis et al 2006, Yang et al 2010, Fourny et al 2016, Jo et al 2021 and in one case sediments (Chauvel et al 2011). In other fields, especially those of construction chemistry and cementitious materials, matrix-matched reference materials with characterised 87 Sr/ 86 Sr isotope ratios are lacking although heavily needed to validate analytical procedures used for provenance studies of these cementitious materials, especially cement, mortar, and concrete (Graham et al 2000, Kazlagic et al 2021, Kazlagić et al 2022, and for possible technological procedures during renovation of historical objects.…”