Concrete densifiers allow some internal migration of moisture, increases density, increases compression and flexural strengths, reduced permeability, protects against acid and calcium chloride contamination and damage, reduces dusting potential, increased abrasion resistance, and does not alter traction quality.
Integrally sealing concrete is a good low cost preventive measure for any concrete structure.
Rough surface removal, repair, and re-profiling is low cost and low cost / risk solution to rehabilitate an old slab at a fraction of the cost of a new slab.
Moisture / freeze thaw / rusting rebar. Very common repair.
Pop outs are a common problem for freshly placed slabs in North America. Sand and aggregates cannot be screened and washed to remove the risk entirely. Many floors have been rectified of this problem over the years.