Comment on “Experimental study on the thixotropic mechanism of deep-sea clay from the perspective of microstructure and bound water” by Ren et al. (2023), Acta Geotechnica, https://doi.org/10.1007/s11440-023-01967-5

Ren et al. (Acta Geotech, 2023. https://doi.org/10.1007/s11440-023-01967-5) recently reported an interesting experimental investigation of the thixotropism, or thixotropy mechanism, of a deep-sea marine clay, conclusively claiming that the conversion of weakly and strongly bound waters to free water, in addition to microfabric change, contributes to the thixotropic hardening of the studied clay. While the microfabric evolution of the clay during the thixotropic hardening process was observed, in a speculative and qualitative fashion, using scanning electron microscopy, the interconversion of different types of waters (i.e., weakly bound water, strongly bound water, and free water) in the clay was quantitatively assessed using thermogravimetric analysis (TGA) and qualitatively judged by Fourier transform infrared spectroscopy (FTIR). However, some fundamental issues related to the viability and suitability of the employed experimental techniques and the interpretation of TGA and FTIR results arise and are worth re-examination and discussion. In this short communication, the TGA curves and FTIR spectra were re-interpreted, based on a mathematically more accurate and scientifically more rigorous analysis of the data, which appears to make the proposed model of evolution of different types of waters in clays invalid. Consequently, the attribution of thixotropy or one potential thixotropism to the conversion among different types of waters and the conclusions drawn based on the speculative interpretations are also worth further clarifying and commenting. Overall, the TGA and FTIR results probably fail to conclusively establish the conversion among the different types of waters occurring along with the thixotropic hardening process.