Diagnosis: Also known as blow-holes, bug-holes are small air-bubble voids on the surface of formed concrete.
Cause: Air entrapped during concrete placement and consolidation. Three main factors contribute to this condition, improper vibration practice, non-permeable formwork and mix design. To prevent bug holes, follow the ACI (American Concrete Institute) published vibration practice standards, use permeable formwork or permeable liners, and choose a mix design with enhanced self-consolidating properties.
Possible concrete repairs:
Structural: Bug-holes are rarely a structural problem, however if not addressed, they can increase the likelihood of future problems.
Aesthetic: The time-honored standard practice for this is a modified rubbed finish (aka sack-rub, or sacking). This involves dressing of the surface to remove form-fins and other raised imperfections, followed by SSD and application of a polymer-modified mortar with sponge floats.