Air lime mortars for conservation of historic tiles: Bond strength of new mortars to old tiles

The present work studies the bond strength between new mortars and old tiles. The influence in tile/mortar bond strength of moisture content of tiles, mortars aggregates grain size distribution and nature, binder/aggregate ratio, different tile ceramic parts, water absorption and porous characteristics of historic tiles and new mortars were evaluated. Laboratory bond strength tests were performed with 6 different types of old tiles and it were performed 3 bond strength tests in situ. Tile/mortar bond strength values rise with an increased moisture content on tile. Most presented mortar compositions are suitable for reapplication of historic tiles as they present bond strength values (≈0,04 MPa–0,10 MPa) similar to in-situ tests.