Crumb rubbers have been investigated as additives to concrete and promising results have been observed. Organosulfur compounds from a petroleum-refining factory were used to modify the surface properties of crumb rubbers. The intermolecular interaction forces between cement hydration products (C-S-H) and rubber crumbs were measured directly by an atomic force microscope (AFM) equipped with a colloid probe. Experimental data indicate that crumb rubber surface is more hydrophilic after the treatment with organosulfur compounds and the intermolecular interaction forces between C-S-H and rubber increase with the treatment of crumb rubbers with organosulfur compounds. Furthermore, these increased interaction forces lead to an increased concrete strength.