Medieval Mortars and the Gothic Revival: The Cosmati Pavement at Westminster Abbey

In the 1870s the architect Sir George Gilbert Scott was appointed Surveyor to the Fabric at Westminster Abbey and one of his major initiatives was to restore the Cosmati Pavement in the Sanctuary. Originally commissioned by Henry III in the late 14th Century, this luxury pavement employed the Cosmatesque technique with materials and possibly artisans imported from Rome. As such, this pavement is the only remaining example if this type north of the Alps, and is one of the very few examples which retains much of its original mortars. These original mortars were developed to cope with the damp conditions of the Thames riverbank and are hydraulic limes which use crushed terracotta as a pozzolana. During the restoration in the 1870s, Gilbert-Scott attempted to replicate the appearance of these materials whilst using contemporary Portland cement mixes with a series of special additives. This paper presents a textural and petrological study, using optical polarising light microscopy, and compares the compositions and manufacturing technologies of the original 14th Century mortars with those of the 19th Century restorations