The composition of cement-based materials in modern historical buildings: The study case of Zhangyuan (Shanghai)

Research on the original materials of modern historical architecture is a relatively novel subject in the field of cultural heritage preservation. However, it differs in research methods from traditional materials. This study takes cement-based materials as an example and delves into two dimensions: literature review and laboratory analysis, elucidating their usage types and material characteristics in modern and contemporary architecture. The literature review demonstrates that in the early stages of cement use, there was a wide variety of types, significant variations in cement material proportions, and widespread use of additives. Regarding physical analysis, focusing on the cement-based materials of the historic Zhangyuan in Shanghai, analyses of concrete components, masonry mortar, cement plaster, and artificial stone were conducted using petrographic and XRD analyses. The results reveal that the mortar aggregates contain sodium feldspar, microcline, muscovite, among others. Different types of components exhibit a certain degree of differentiation in fine aggregate types. Due to the carbonation reaction of cement, the cementing materials in the mortar have essentially transformed into calcium carbonate, primarily as calcite, with mass fractions mostly ranging from 15% to 25%. Typical cement hydrates were only detectable in certain specialized cement materials. Combining literature research with laboratory analysis, it can be concluded that in the early use of cement, due to control over engineering economics and inadequate material understanding, the sand content and water-cement ratio of cement mortar were higher than the standards. Additives primarily consisted of lime, with the likelihood of later causing material deterioration. Large particles and incompletely reacted cement clinker particles can serve as distinguishing features of early cement-based materials. These findings might represent common phenomena in the materials of modern and contemporary historical architecture, urging practitioners in the field of cultural heritage preservation to emphasise.