Prestressed Concrete: Classes, Environments, Reinforcement, and Roofing

Prestressing Classes and Environments

Classes

• Class I: Elements whose conditions of use require the absence of cracking.
• Class II: Elements whose conditions of use can accept some risk of cracking under certain conditions.
• Class III: Elements whose conditions of use can support a controllable amplitude of cracking.

Environments

• I: Inside buildings or outside of moisture.
• II: External, non-aggressive contact with water or ground.
• III: Aggressive atmosphere, industrial or marine, or land contact with water or aggressive substances.

Active Reinforcement Types (P)

• Wire: A product of solid section from a cold drawn or drawn from alumbrón, normally supplied in a roll. Diameter: 3, 4, 5, 6, 7, 7.5, 8, 9.4, 10 mm.
• Bar: A solid product that is supplied only as a straight wire.
• Strand of 2 or 3 wires: A set of 2 or 3 wires with a nominal diameter, helically wound, with the same pace and direction of torque on a common shaft. Diameter: 5.2, 5.6, 6, 6.5, 6.8, 7.5 mm.
• 7-wire rope: A set of 6 wires of equal nominal diameter, helically wound with equal pace and in the same sense of twist around a wire whose diameter is 1.02 to 1.05 times the nominal diameter. Diameter: 9.3, 13, 15.2, 16 mm.

Roofing

Inclined Roofs

Industrial and non-industrial.

Flat Roofs

With heavy forged, accessible (not walkable), light (straps and plates).

Tile

Slope less than 20%, with tar paper, the overlap of 8-15 cm between tiles, the tile will have a 7 cm eave, and a separation between blankets of 3 cm.

Sheet Metal

• Sandwich Panel: Composed of sheet metal, insulation, and sheet metal. Profiles are placed between the plates.
• Prefabricated Panel: This is a panel composed of two sheets of 5 mm, holding each other with 4-5 cm of polyurethane. The lower plate forms the ceiling, and the upper plate forms the deck. Note: Static resistance, thermal conduction, and sound transmission are important. The number of fixations and tightness are very important.
• Deck Cover:
  1. Profiled support base plate.
  2. Vapor barrier (thin sheet).
  3. Insulation (rock wool, expanded perlite, cellular glass).
  4. Waterproofing (bituminous sheet: monolayer, multilayer, multilayer in-situ; synthetic: PVC, rubber).
  5. Protection (heavy "gravel", self-protection mineral, metal self-protection).

Types of Prestressing

• Pre-tensioned Reinforcement: The reinforcement is provisionally anchored and tightened. Concrete is poured and allowed to gain strength. The reinforcement is then released, and the force is transmitted to the concrete by bond.
• Post-tensioned Reinforcement: The concrete is poured, leaving ducts. When the concrete has gained sufficient strength, the reinforcement is tensioned and anchored. Types: adherent and non-adherent.