Fingerprinting Portland cements by means of 87Sr/86Sr and 143Nd/144Nd isotope ratios and geochemical profiles

Abstract

This study uses conventional 87Sr/87Sr and 87Nd/87Nd isotope and interelement ratios of Ca, Sr, K, Mn, Mg, and Ti as fingerprints for ordinary Portland cements (OPC) provenancing. Herein, the first database of Sr and Nd isotope ratios investigated in OPCs stemming from twenty-nine cement plants located worldwide was created. The results show that the Sr isotope ratios of OPCs are higher than those of seawater from the observed geological period. The spread of 87Nd/87Nd in OPCs is not as large as the spread for 87Sr/87Sr isotope ratios. However, the combination of both Sr and Nd isotope ratios provides the potential for distinguishing between cements of different production sites. Most of the investigated OPCs have measurable differences in their 87Sr/87Sr and 87Nd/87Nd isotope ratios, which can be employed as a valuable analytical fingerprinting tool. In the case of equivocal results, Divisive Hierarchical Clustering was employed to help overcome this issue. The construction of geochemical profiles allowed computing suitably defined distances between cements and clustering them according to their chemical similarity. By applying this methodology, successful fingerprinting was achieved in 27 out of 29 analysed ordinary Portland cements.