dry additive for gypsum and process for its preparation

dry additive for gypsum and method for producing characterized in that it consists of a base polycarboxylic acid, more particularly citric acid, to which is added colloidal silicon dioxide in proportions of between 0.8% and 1 , 2% by weight based on the acid. The proposed additive is presented in dry powder form, so that mixing with the plaster whose properties are intended to improve be performed before mixing with water can incorporate the additive in the dry mass of gypsum during manufacture. The process for obtaining passes through the arrangement of a base of citric acid presented as solid crystals to which is added colloidal silicon dioxide in the proportion indicated later mixing to obtain a homogenous color and texture.