[concretemasonry]

You should use mortar for the joints under and between the caps. - Gout is only used to fill the cores of the block. Tool the joints with a convex to to give a tighter joint.

The wall does appear to be built using mortar and grout, so it is classified as a "rigid" wall.

If you had used mortarless interlocking retaining wall units with no mortar, you would use dabs of silicone adhesive to adhere the caps since it would be classified as a "flexible" wall that can adjust to temperatures and moisture movement.

Dick

 

[concretemasonry]

Use the same 3/8" joint that was used on the split face block for the wall. Use the same mortar color also.

Dick