a process and compositions for improving the resistance of cementitious products such as concrete , mortar , grout , paving , paving blocks , concrete pipe , concrete blocks , cellular concrete , extruded roof concrete , shot crete and concrete statuary to the penetration of water utilizes a minor amount of aqueous emulsion of rosin or a waxy substance in a major amount of water to form a substantially aqueous mixture utilized as the aqueous ingredient in the preparation of the cementitious product . the composition of an aqueous emulsion of rosin or a waxy substance , water , cement and aggregate provides , in addition to improved resistance to the penetration of water , maintains the strength of the cementitious product and can provide a vehicle for adding property enhancing agents to the cementitious product .