Mortar between masonry units consists of cement, lime, and sand. These materials are used in different mix proportions. For example, a lower strength mortar of this type would have a proportion 1:2:9 cement:lime:sand, and a higher strength mortar would have proportions of 1:1/2:3 1/2 cement:lime:sand. This mortar has a similar colour as cement:sand mortar. Lime is usually added to improve workability at the time of construction, but it does not improve strength.