Q.: We have a problem with popouts on some rather expensive steps and landings in a church building and the owners are withholding the releasing of the bond. Can you recommend a way to repair them?
A.: Popouts are troublesome in that they are frequently a delayed action phenomenon. The concrete may sometimes be a year or more old before popping begins to appear. Then it may continue over an indefinite period of time covering several additional years. Structurally popouts are of little or no significance. They are, however, troublesome in terms of appearance. If the steps and landings that you are concerned about must be repaired to satisfy the owners requirements for appearance, you may have to resurface with concrete. An alternative might be to put on an epoxy mortar topping but I would not do so without substantial technical aid from a reliable epoxy toppings manufacturer. Before doing anything you may wish to try to satisfy yourself that popping has come to an end. It is possible that you have not seen the last of the popouts on this job.
It is normally the aggregate close to the surface that causes popouts. If you take off one inch or more and then put a good concrete topping that is free of susceptible aggregates over the surface you may be able to prevent further popping caused by the aggregate in the base course.