If blisters do form, which action should you take?

If blisters do form, which action should you take?

• A. Flatten the trowel blades or reopen the surface with a wood float and delay further finishing for as long as possible
• B. Flatten the trowel blades and finish immediately with a steel float
• C. Remove blisters with sandpaper and resume finishing
• D. Ignore blisters and continue troweling freely

Answer: (A)

Blisters form when moisture or trapped air pushes up through the surface of fresh concrete. The right response is to back off from finishing and rework the area by flattening the blistered skin with the trowel blades or, better, reopening the surface with a wood hand float to pop and level it. After this rework, delay further finishing until the surface stiffens a bit and bleed water can escape. This pause helps prevent pushing moisture to the surface again and avoids creating weak spots. Finishing immediately with a steel float would burnish or smear the blister, trapping moisture and making the defect worse. Removing blisters with sandpaper only removes the top layer without addressing the moisture issue, and ignoring the blisters lets defects propagate, leading to cracks or delamination.

Blisters form when moisture or trapped air pushes up through the surface of fresh concrete. The right response is to back off from finishing and rework the area by flattening the blistered skin with the trowel blades or, better, reopening the surface with a wood hand float to pop and level it. After this rework, delay further finishing until the surface stiffens a bit and bleed water can escape. This pause helps prevent pushing moisture to the surface again and avoids creating weak spots. Finishing immediately with a steel float would burnish or smear the blister, trapping moisture and making the defect worse. Removing blisters with sandpaper only removes the top layer without addressing the moisture issue, and ignoring the blisters lets defects propagate, leading to cracks or delamination.