Longer panels are better???
We at Hawk frequently go out to do repairs of our competitors wall, so we have the opportunity to see a lot of walls and the problems that those walls face. Being a manufacturer of these walls, these issues allow us to modify our walls to ensure that these issues are mitigated, if not eliminated.
One frequent issue we constantly see is a certain panel that is 16 feet long standard. The industry has promoted longer panels as the way to reduce costs due to needing fewer columns; good idea in theory. These longer panels when supported from the ends put a great deal off tension stress at the bottom of the panel and a lot of compression stress at the top. Concrete is really great at handling compression, but not really good at the tension part. A good rule of thumb is that concrete, in tension, can hold 10% of its compressive strength. If you have concrete that is claimed to be 5000 psi, it would be able to hold about 500 lbs of tension. Well, that long wall has a tendency to pull pretty hard; you see, a typical 8 foot tall panel at 16 feet long may weigh 8000 lbs. With that kind of weight, only sitting on its ends, stresses that panel pretty hard.
Many customers of these types of walls ask us to come out and fix these panels, unfortunately we cannot, we can only either band-aid it by supporting the bottom, or use our Verti-Crete Screen Wall System as the replacement. It is difficult for a customer of this product to invest a lot of money into these walls only to come back in a year and start to see these types of cracks, we think its a shame as well.
Concrete will crack, but we should not help it crack. Manufacturers should be building these walls with enough support at the bottom of the panel by using steel rebar. Rebar is real good in tension and will help the concrete hold that load. Some also try to use fiber reinforcement to help with cracking as well, but with a big panel, it is not a replacement for rebar. If you see a big panel with little 'stringies' at the top of the wall, ask your manufacturer if there is steel in there too. It would not be uncommon to forego the steel all together and just use the fiber to help cut costs and try to bet the job, that usually would reveal itself in a matter of time.
It is unfortunate that the drive to reduce costs will go so far as to compromise the long term condition of a wall and your investment. We encourage our customers to ask what is in the wall and what the manufacturer is doing to prevent and mitigate cracking. Ask how strong that concrete is and ask them to prove it.