psi required to remove lightweight concrete from molds

[MDGREENWRLD]

We have a cellular, foam entrained mix for a pre-cast panel application that has about 45-55% air by volume. Ultimate strengths needed are 1200-1500 psi, and we can hit 550 psi within 24 hrs. At what strength can we effectively break out product from the molds? This can obviously be verified through experimentation, but we are not yet in production of this product.

 

[Ron]

550 psi should not be a problem with mold removal.

 

[concretemasonry]

MDGREENWRLD -

Your problem sounds similar to AAC where the molds are designed to be removed FROM the concrete for further use (cutting, dimensioning, etc.).

Have you looked into the processes that have been used for decades on many construction materials? some are two stage system and others are a single curing operation and details that cannot be form are carved out in a separate process prior to packaging or delivery.

Usually, these products are produced in a very sophisticated plant with fine tuning of the mixes and processes to be able to adapt to different products after research and actual production using the same materials anticipated.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Ron]

mdgreenwrld...I answered before based on removal from test specimen molds...I re-read your post and see that you are asking about product removal from molds....could be a big difference...sorry if I mislead you.

Yes, experimentation will be your better guide for this. It will depend on the geometry of the product, how vigorous the removal process has to be and how the product is supported during removal. Obviously, if the product can be fully supported during removal so that no bending stresses are introduced, it would be better. It would also be better to remove the mold from the product, not the product from the mold.

 

[cvg]

you should check tensile strength, not compressive

 

[MDGREENWRLD]

Thanks for the replies. Yes, the tensile strength is more important. The mold is cast horizontally in a twin configuration. It is supported during breakout, and three of four sides are removed. There will be some stress pulling the unit laterally from the fourth side. However, the greatest stress introduced is lifting vertically from the mold. The long axis of the panel is in the greatest danger of failing if the product was too green. The key will have to be the clamping and support mechanisms during this lifting process.