Application of mortar to wrap coffins in ancient Chinese tombs: Their properties, compositions and protective effect for the buried objects

The study analyses the different kinds of sealing materials that wrapped coffins, examples of which were excavated from several Chinese tombs. The mineral compositions, microstructure and properties of these materials were assessed by means of scanning electron microscopy with energy‐dispersive spectroscopy (SEM‐EDS), differential scanning calorimetry with glass transition (DSC‐TG), X‐ray powder diffraction (XRD), as well as mechanical and weather resistance tests. The results showed that the historical cement concrete had best overall performance due to its compact structure. This concrete contains more calcium and aluminium, and most likely belongs to old artificial white Portland cement. The properties and structures of lime mortar were related to the content of lime and the kinds of organic additives. Although the ancient people perhaps had found these rules, subject to social productivity, the optimum lime mortars were not widely used. As a natural sealing material, green paste mud had been used in this field for a long time. It consisted of microcrystalline muscovite, feldspar and quartz. Its strength, sealing and water resistance were better than ordinary soil, but the stability was general. Thus, it was gradually replaced by hybrid artificial materials.