Waffle Surface Problem in PS Conrete Beam
Waffle Surface Problem in PS Conrete Beam
(OP)
I have a weird concrete problem that I have never seen before; any advice or thoughts would be appreciated. It is a prestressed, large (2'-6"deep, 6'-0"wide, 20' long) concrete beam, simple span (so PS strands towards bottom), longitudinal mild reinforcing towards top, #5 full circumference stirrups, 7 ksi concrete, 1.5" min. cover (which was special inspected, so not likely to be shortchanged on cover). The contractor used steam curing. When the steaming tarps were removed, it was noted that a "waffle" pattern had developed in the top face of the beam, with low points occurring directly over reinforcing (especially the stirrups). Any ideas why? Or similar problems experienced? My first intuition was that they should not have used steam curing for mass concrete, but I do not have any theory handy that would explain such a phenomenom. Thank you...






RE: Waffle Surface Problem in PS Conrete Beam
1.5" of cover over reiforcing bars is somewhat shallow. It could be that due to the shallow cover there is less than the desired amount of aggregate available over the re-bar. In concrete, shrinkage occurs in the cement paste, aggregate will not shrink.
RE: Waffle Surface Problem in PS Conrete Beam
RE: Waffle Surface Problem in PS Conrete Beam
RE: Waffle Surface Problem in PS Conrete Beam