A method of making a cementitious composition that includes combining cement, water and optionally aggregates and optionally additives to form an aqueous cement slurry; adding expanded polymer particles to the aqueous cement slurry; and forming a dispersion of expanded polymer particles in the aqueous cement slurry. The expanded polymer particles have an average particle diameter of from 200 .mu.m to 5,000 .mu.m, a bulk density of from 0.02 g/cc to 0.64 g/cc, and an aspect ratio of from 1 to 3.