Durability improvement of ancient bricks by cementation of porous media

Time-dependent natural weathering processes suffered by historic bricks in Toledo (Spain) improve their physicomechanical properties by porous infill with gypsum, ettringite and mainly calcite. Both, these bricks and their experimental replica bricks, made from the original calcareous clays fired at the probable historical temperatures (700o 900oC), have been analyzed by X-ray diffraction, optical and scanning electron microscopy, mercury intrusion porosimetry and ultrasound velocities to compare pore structure and strength evolution by mineral cementation. The resultant microstructure and mineral fillings depend on brick calcareous composition and firing temperature, the brick location environment, burial, indoor or outdoor walls, the lime-based joint mortars and coat plasters and infiltration waters.