What is the most important mortar property?

• A. Compressive strength
• B. Bond strength
• C. Color
• D. Workability

Answer: (B)

The most important mortar property is its ability to bond masonry units together. Bond strength measures how well the mortar adheres to the faces of the bricks or blocks and fills the joints so loads and stresses can be transferred across the wall. When the bond is strong, the masonry behaves as a single connected system, resisting vertical loads, wind, and seismic forces, and preventing units from sliding or separating at the joints. If bond is weak, cracks form at the mortar–unit interface, joints can open, and the overall stability of the wall suffers—even if the individual bricks or blocks and the mortar mix have decent strength.

Compressive strength of mortar matters, but the wall’s overall strength is driven more by the interaction between units and mortar than by mortar strength alone. The emphasis is on achieving a continuous, durable bond rather than just a hard mortar. Color is purely cosmetic and has no bearing on performance. Workability is important for proper placement and finishing, which supports good bonding, but the decisive factor for structural performance is how well the mortar bonds the units.