What is the primary aggregate used in masonry mortar?

The primary aggregate used in masonry mortar is sand. Sand plays a crucial role in the formulation of masonry mortar, primarily because it provides workability, strength, and stability to the mixture. The grains of sand help to ensure that the mortar can be easily spread and shaped during application, allowing for good bonding between masonry units such as bricks or blocks. The texture and size of the sand particles are also important; they should be clean and well-graded to achieve a strong and durable mortar.

In contrast, gravel is too coarse for masonry mortar, as it would create a mixture that is more difficult to work with and might not bond well with the masonry units. Silt can hold moisture but does not provide the necessary structural integrity for mortar; too much silt can also lead to shrinkage and cracking. Clay, while used in some types of mortar, is not the primary aggregate. It is typically associated with brick-making and can affect the mortar's cohesion and water retention negatively when used in excess.

Overall, the choice of sand as the primary aggregate in masonry mortar is essential for achieving the proper consistency, bonding, and durability required in masonry construction.