Why Prestress the Exterior Layer of Insulated Wall Panels?

 

Did you know that many precast concrete wall panel manufacturers do NOT prestress their exterior layer in an insulated sandwich wall panel?  In fact, some precasters don’t even use mild reinforcement (steel).  They do this because it either cuts costs and/or they don’t have the capabilities to do so.  Either way, it’s a loss for the customer.  There’s probably a good majority of people who don’t even understand the benefits of having a prestressed architectural layer.  I’ll try and explain…

Although reinforced concrete is generally a better construction material than the ordinary stuff, it’s still brittle and liable to crack in tension.  Reinforced concrete can fail in spite of its steel, letting water in, which then causes the concrete to deteriorate and the rebar to rust.  The solution is to put concrete permanently into compression by prestresssing (also called pretensioning). Compression is the cunning trick that helps to stop cracking (and stops cracks from spreading if they do form).

Other Benefits of a Prestressed Exterior Wythe:

  • Aesthetically more pleasing panels due to the absence of cracks
  • Improves structural capacity and handling capabilities
  • Allows for composite design without the use of solid concrete (which is a big deal in colder climates)
  • Can reduce the required structural layer thickness
  • Helps resist thermal bowing along with camber & deflection issues
  • Higher strength concrete is provided to ensure the bonding of the strand

Dave Eilertson
Sales – Southern Minnesota/Southern Wisconsin