We are building wall panels from concrete for a custom job. I am making 2' x4' forms 7/8" thick to pour cement in. I would like to keep it lite and also am concerned about cracking because we have to ship it to the job when finished. I was thinking about using "Dens Shield" from Georgia Pacific or "Durock" to set in the cement to keep it stiff and lite (used in tile setting), that will leave only about 3/8" of cement on top or the face side.

Can I pour it that thin and keep it from cracking? Can you suggest a mixture.

Can you send answer to this address instead of one I mailed from?
Thanks for any help!   JM

3/8" thick concrete topping?  The problem will be to get the concrete to bond securely to the panels.  I can see a big problem with the concrete below the board since a lot of air and water will be trapped at the interface.  It might work if you could find a board that has holes in at least half its surface.  This way there will room for the air/water to escape and the two sides will bond.

Even 7/8" is very thin for concrete.  You will not be using any aggregates larger than 3/8", and will need relatively high strength (above 5000 psi).  The mix design depends on the materials available to you in your area and your best bet will be to get your concrete supplier to pull out of his archives a proven mix.  There is no way I could do that without all the local info and extensive experimenting.

If you do not have a proven mix design, you will have to spend a lot of time and money getting the mix to exactly what you need.  I can imagine that the penalty for cracked panels can be expensive.

You may want to consider using fibers (such as Fibermesh) to stiffen the concrete for transport.  A layer or two of "chicken wire" centered in the panel will also help.  I would have recommended using actual rebars, but this panel is too thin.  Even if you use #3 bar (3/8") you will have less than 1/4" cover of concrete on the steel.  This will cause corrosion and cracking problems.

An option to consider will be to use light-weight aggregate.  You can reduce the weight of the concrete panel from 1000 lbs to 750 with commonly available aggregates.  Further reduction can be achieved by entraining air.