Conventionally reinforced concrete is concrete strengthened with ordinary steel reinforcing bars (rebar) that are not tensioned, in contrast to prestressed systems such as post-tensioned or precast pretensioned concrete.
The rebar carries the tension that concrete cannot. Because nothing squeezes the concrete together, it cracks more readily under load and shrinkage. That is acceptable in many buildings, but in a parking structure cracks let water and deicing salts reach the steel. For that reason it is used more for foundations, columns, walls and short spans than for long-span parking decks.
Where it fits
- Foundations, columns, shear walls and below-grade structures.
- Short-span floors and podium levels under buildings.
- Ramps, stairs and other elements that are hard to prestress.
Protecting it in a garage
- Low-permeability concrete with enough cover over the bars. See concrete.
- Epoxy-coated or galvanized reinforcing in exposed decks.
- Penetrating sealers or traffic membranes on driving surfaces.
- Routing out and sealing cracks as part of routine maintenance. See chloride-ion contamination.
The Parkonomics view
Rebar is not the problem; water reaching rebar is. Whatever the structural system, a garage lasts as long as its owner keeps salt water away from the steel.
Related terms: Post-Tensioned Concrete, Precast Concrete, Concrete, Chloride-Ion Contamination, Structural Systems of Parking, Spalled