Our brick walk is 30' long and approx. 17 yrs old. At 5 places, the mortar is either loose or missing on a few bricks. It appears that only about 1 inch of the mortar is missing. The remaining mortar seems solid when I pick at it with a screwdriver.

My question is, can I simply add mortar like Sacrete or do I have to remove the remaining mortar? Also, what preparation is needed?

Thanks