Physico-chemical characterisation of bricks all through the manufacture process in relation to efflorescence salts

Due to the high competitiveness of the ceramic product market, quality and technical requirement are increasing. The efflorescence problem is a phenomenon that affects the aesthetic quality of brick facades and which is not easily dealt with. The aims of this work are to study the key physical and chemical parameters for this phenomenon in all activities of the brick manufacturing process and to evaluate the influence of the additives employed on the appearance of the efflorescence phenomenon. Porosity and specific surface, mineralogical analysis, total chemical content and soluble salts were determined on green, dried and fired brick, both when no additives were added to the manufacturing process and also when ammonium lignosulphonate and barium carbonate were used as additives. The main mineralogical phases and water soluble salts in the efflorescence phenomenon have been obtained. In some cases, relationships between soluble salts in the end product and soluble salts in the efflorescence have been established. From the obtained results, the use of a mixture of ammonium lignosulphonate and barium carbonate together with the control of the firing process variable is recommended in order to prevent this phenomenon.