Method of using highly concentrated aqueous solutions of low viscosity of melamine/aldehyde resins for improving building materials

A method of increasing the quality of building materials by incorporating therein a highly concentrated aqueous solution of low viscosity of melamine/aldehyde resins, prepared by reacting to a precondensate in a first step melamine and an aldehyde in an alkaline medium and in the presence of water together with at least one compound (I) selected from the group consisting of an alkali sulfite, an alkaline earth sulfite, an amino sulfonic acid, an amino carboxylic acid, a hydroxycarboxylic acid, a hydroxycarboxylic acid lactone, and a polyhydroxy carboxylic acid lactone then reacting the thus obtained mixture in a second step with at least one compound (II) selected from the group consisting of an amino carboxylic acid, a carboxylic acid, a hydroxy carboxylic acid, a hydroxy carboxylic acid lactone, an amino sulfonic acid including sulfamic acid, a polyhydroxy carboxylic acid and a polyhydroxy carboxylic acid lactone, and then making alkaline the obtained resin solution by adding at least one basic compound (III), said building materials consisting of inorganic binders and additives, in an amount of from 0.01 to 25% by weight, relative to the inorganic binder.