Synthetic latex for additives to cement grouts, totally replacing water in the mix. It limits the water absorption of joints and gives the grout greater adhesion to tile sides, abrasion resistance, workability, flexibility and compactness. It is particularly suitable as an adjuvant for sealing joints in balconies, terraces, swimming pools, outdoor facades, showers, bathrooms, industrial and commercial floors subject to heavy traffic, floors and walls subject to frequent washing.