Chemical and mineralógica! study of restoration mortars applied to the Eocene sandstones of Gipuzkoa used for building construction

We have chemically and mineralogically analysed four commercial mortars (A, B, C and D) and a fifth one (synthesised by Teusa) by means of X-ray fluorescence and X-ray diffraction techniques. The mortar A is an amorphous arid-free alite-mortar, whereas the B and C are composed by quartz, alite and calcite. The mortar D is particularly special because of its composition of calcite and zincite together with minor amounts of quartz. The establishment of the precise chemical and mineralogical composition of mortars is an essential tool to enlighten the suitability of each type of mortar when applied to a particular rock for building. Most mortars have alite, quartz and calcite, appearing portlandite after 28 days of hardening. The low cristallinity of the mortar A, together with its chemistry suggests the presence of pozzolan. The mortars B and C have variable amounts of quartz as arid, being the C enriched in Ti, which appears as rutile. Probably the presence of Ti is to color the product. Mortar D is enriched on zincite that becomes simonkolleite after hardening, most probably due to reaction with the binding liquid that is added. The Teusa mortar has been synthesised in four different varieties by modifying the proportions ofhigh-Ca lime, white cement and grey cement. All the four varieties recorded the quartz as the main component together with alite, portlandite and calcit