Although in ancient times masonry was often erected without mortar, the Romans discovered the benefit of using cement in making mortar to produce masonry structures which were stronger and more durable.

Contemporary Masonry Mortar is composed of cement, lime, sand, and water. The quality of the mortar depends upon the quality of its constituent parts, and the proportion of each affects the physical properties of the mortar. Each ingredient brings something different to the mix. Cement gives mortar its strength and durability; lime provides water retention, set control, and elasticity; sand acts as an inexpensive filler; and water contributes plasticity. Entrained air in the cement improves the mortar's resistance to freeze and thaw cycles.