Durability improvement of ancient bricks by cementation of porous media

Abstract

The physicomechanical properties of historic bricks in Toledo (Spain) that have undergone a time-dependent self-healing by natural weathering processes have been improved 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 appropriate historical temperatures (700°–900°C), 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 the 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.