Chromatic alteration of Roman Heritage in Aosta (Italy)

The conservation study of the Roman Heritage in Aosta (Italy) is aimed at understanding the causes of the superficial chromatic alteration, which has affected the Roman ruins (I sec a. C.) since the last decades. The Roman monuments are built of pudding stone, a quite irregular and inhomogeneous conglomerate of fluvial origin. The stone in place started showing superficial chromatic alteration as reddish and pinkish areas in the last fifty years only. First results show that the alteration might be due to the oxidation of ferrous ion. The iron oxides spread out in the secondary calcite, thanks to fluid circulation through porous material, and crumble the pudding stone surface.