The role of brick pebbles and dust in conglomerates based on hydrated lime and crushed bricks

Phoenicians were probably the first ones to use mortars based on hydrated lime and crushed or dust bricks, followed by all other people who were in contact with them. The Romans employed those mortars any time they needed a rendering exposed to severe environment or a floor at a very humid ground level, in foundations where the water table was high or for thermal baths. The use of brick dust in a lime mortar is, nowadays, generally interpreted as an alternative to pozzolana or to other pozzolanic materials. The authors themselves have found, some years ago, clear reaction layers at the contact between the binder and the brick pebbles. Those bricks were found to be mostly pozzolanic under a pozzolanicity test. In some cases, the test gave negative results; nevertheless, the mortars were compact, strong, better than the normal putty lime mortars even when very thick joints were realized, as in the case of the Byzantine buildings. The authors are exploring the possibility of other roles played by the bricks, especially in the case of very thick joints, perhaps producing a good bond while also serving as aggregates and giving overall good physical and mechanical performances to the mortars. Some mortar specimens made from hydrated lime and crushed bricks with chosen size and distribution have been prepared together with a specimen made from large bricks and thick mortar joints. The carbonation process and the strength and deformability at different curing times is explored experimentally. (C) 1997 Elsevier Science Ltd.