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

This study uses conventional Sr-87/Sr-86 and Nd-143/Nd-144 isotope and interelement ratios of Ca, Sr, K, Mn, Mg and Ti as fingerprints for provenancing ordinary Portland cements (OPC). Herein, the first database of Sr and Nd isotope ratios investigated in OPCs, stemming from 29 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 Nd-143/Nd-144 in OPCs is not as large as the spread for Sr-87/Sr-86 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 OPCs investigated have measurable differences in their Sr-87/Sr-86 and Nd-143/Nd-144 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 the computing of 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 the 29 ordinary Portland cements that were analysed.

Automated summary

This study uses isotopic and interelement ratios of Sr-87/Sr-86 and Nd-143/Nd-144, combined with Ca, Sr, K, Mn, Mg, and Ti, to identify the origin of ordinary Portland cements (OPCs). A database of Sr and Nd isotope ratios in OPCs from 29 cement plants worldwide was created. The results show that OPCs have higher Sr isotope ratios compared to seawater from the observed geological period. The combination of Sr and Nd isotope ratios can distinguish between cements from different production sites, and divisive hierarchical clustering was used to overcome equivocal results. The successful fingerprinting of 27 out of 29 OPCs analyzed was achieved through this method.