In masonry, what is the primary role of lime in mortar?

In masonry, lime plays a critical role in improving the pliability of mortar. When lime is added to the mix, it enhances the workability and flexibility of the mortar. This is particularly important for masonry because the materials being used—like bricks or stones—are subjected to various loads and movements. The ability of the mortar to accommodate these movements without cracking is essential for the durability and integrity of the structure.

Additionally, lime helps to create a smoother mix, which aids in achieving better adhesion between the masonry units. This can lead to a stronger overall bond and contribute to the longevity of the construction. In contrast to the other possible roles mentioned in the choices, lime does not primarily serve to increase compressive strength, reduce costs, or enhance color, focusing instead on the crucial aspect of pliability which is vital for effective masonry work.