Concrete can be prone to cracking, but adding a styrene-butadiene latex reduces this tendency, with the styrene providing tensile strength and the butadiene adding elasticity. When water exposure is likely it's often wise to step up to a carboxylated styrene-butadien latexes like Tylac®. With the additional cross-linking and hydrophobicity promoted by carboxylic acid, this improves moisture resistance, making it ideal in situations where cement, tile mortar or grouts are likely to get wet.
When resistance to UV light is needed, typically for exposure outdoors, turn to Rovene® acrylic polymers. Being acrylic-based, these don't degrade, and also offer good resistance to oils and solvents.
Rovene 4040 is a non-carboxylated styrene-butadiene emulsion designed for use as a concrete modifier. It is used as a tile grout mastic modifier where it enhances adhesion.