Tracing carbonation in cementitious slurries is very necessary, as it helps to accurately design the durability of infrastructure and achieve carbon neutrality. In this study, anthocyanins extracted from fresh or stale Orychophragmus violaceus (O. violaceus) flowers on campus were prepared, and their capability as substitute of phenolphthalein, to trace carbonation in cementitious materials was studied. Anthocyanin extracted from stale petal had undergone significant deterioration, while that extracted from fresh petal could be cryo-preserved effectively for at least one year. Combining pH, chemical and porosity analysis, the reliability of the novel anthocyanin indicator in tracing carbonation was verified. With the increase of discoloration pH, the carbonation depth read from anthocyanin contained partial carbonated zone, thus was larger than those read from phenolphthalein. Moreover, the varied evolving pattern on the spatial distribution of local saturation degree in cementitious slurries during carbonation was studied, based on which factors affecting the broadness of partial carbonated zone were offered, and circumstances under which anthocyanin would be more accurate than phenolphthalein were offered. For conditions where a broad partial carbonated zone is presented or a condition where higher standard on human safety is required, the new-developed O. violaceus indicator is more competitive over phenolphthalein.
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