Formliners are a cost-effective method for creating patterned or decorative concrete walls, sound barriers, and retaining walls. Some formliners are intended for only one use, though many are meant to be used again and again, representing a longer-term investment in this construction method. However, it is rare to get much more than 30 uses out of a formliner. To protect that investment, Ed Fitzgerald, of Fitzgerald Formliners, knows a few tricks you can use to make them last longer.
It's important to care for your form-liners. Cleaning off the release agent between pours is a simple way to make them last longer, Fitzgerald says. Some release agents can be reactive, degrading the formliner over time. Cleaning the formliner also removes any concrete dust that can be unwanted for the next pour.
When coating the forms prior to placing, Fitzgerald recommends wiping down the formliner surface with a rag soaked in the release agent after first spraying on a layer of the release agent. And remember to get under blades or any overhanging relief. This ensures the release agent gets into all the crevices, completely covering the form. However, more release agent is not necessarily better, he says. Excessive use of release agents can cause bug holes.
Using nails to fasten the formliner to the form is an easy way to shorten the lifespan of the formliner. Screws are much better. In addition, the fewer times you need to remount the formliner on the form the better. If you must, try to reuse the same holes. Otherwise, the more holes you make in the formliner, the more you need to patch the old holes. And naturally, a form-liner with many patches doesn't look as good as one with no patches.
Formliners are not the same as plain plywood form panels. Fitzgerald says to be careful not to peel back the formliners during stripping. This can put undue stress on the bottom of the form, reducing its usefulness over time. Formliners won't simply “pop off” like flat panels.
When placing the concrete, always remember to use a tremie to cut down on segregation. And don't forget to vibrate the wall segment to eliminate voids.
It is also important to consider carefully the wall ties, especially when using a plasticizer in the mix. Higher head pressures require stronger wall ties. There are many types of ties, as well as situations where choosing the right one is important. Contact your form-liner manufacturer for help.