Why isn’t the water retention of masonry mortar the higher the better

The water retention of masonry mortar is important because it affects the workability, consistency, and performance of the mortar. While it is true that water retention is an important property, it is not always the case that higher water retention is better. There are several reasons for this:

1. Workability: High water retention can lead to excessively wet and sticky mortar, which can be difficult to work with and may cause issues such as sagging or slumping of the mortar during application.
2. Bond strength: The water-to-cement ratio is a critical factor in determining the bond strength of mortar. Excessively high water retention can lead to a higher water-to-cement ratio, which can reduce the bond strength of the mortar.
3. Durability: High water retention can also affect the durability of the mortar. Excess moisture can lead to increased water absorption and potential freeze-thaw damage in colder climates.
4. Shrinkage: High water retention can also lead to increased shrinkage and cracking of the mortar, which can compromise the integrity of the masonry structure.

In summary, while water retention is an important property of masonry mortar, it is not always the case that the higher the water retention, the better the performance of the mortar. Balancing water retention with other important properties such as workability, bond strength, durability, and shrinkage is essential in achieving a high-quality mortar that meets the needs of the specific application.