Tuesday, December 16, 2008
I've always been somewhat surprised by the Corps of Engineers continued use of PVC dumbbell waterstop in their flood control and dam projects. After Hurricane Katrina hit, and large portions of floodwall needed to be repaired or replaced, the COE's design still called out for this largely out-dated style of waterstop. Dumbbell waterstop functions like a cork in a bottle, with the large end bulbs simultaneously acting as both anchors and internal dams. Historically, dumbbell waterstop is one of the leakiest varieties of waterstop, as the large end bulbs when pulled under tension distort to an elliptical shape, while the concrete cast against them remains in a round shape and therefore creates an annular void for water to migrate through.
Now, large portions of the rebuilt floodwall in Kenner, LA are leaking and expensive repair procedures are taking place. I would imagine that simply by specifying a ribbed centerbulb waterstop this entire failure could have been avoided.
Tuesday, December 09, 2008
JP Specialties, Inc. has developed a new Earth Shield® waterstop product specifically designed to accommodate large shear movements, such as tank ring foundations subjected to settlement. The JP621L Retrofit Waterstop System is chemically and mechanically adhered to the existing concrete using one of our chemical resistant, novolac epoxies (VEN500 or VEN1000), stainless steel batten bar, and stainless steel anchor bolts. The waterstop profile is combed along the fastening leg, which facilitates the epoxy bonding to the profile. The embedded waterstop leg has two large polymer dams which are designed to create a torturous fluid path and simultaneously perform as anchor points for the new concrete to bond to. The JP621L profile has a large, tear-web centerbulb that can move greater than five inches without deformation of the waterstops main body. (The thin diaphragm, or "tear-web", ruptures under shear stress, allowing the "U-bulb" to move freely for its entire length when installed in an open joint.) JP621L Retrofit Waterstop can be heat welded to a continuous, fluid-tight barrier, like all our Earth Shield® waterstop profiles, and can be joined to our baseseal (or rearguard) profiles for intersecting joints.