Mix proportion of cast-stone vs. precast concrete?

[ljiang]

Hello, folks,

I am doing a new research project regarding to the " Cast-Stone". I have read all the specifications of cast stone from cast stone institute, but still did not get clear idea about how to do mix design of cast stone. I understand that the requirement of physical properties is a little bit different between the cast stone and arthitectural precast concrete regarding to the strength and freeze-thaw resistance. But is the mix design method is similar?

Moreover, About aggregates, it is said in the specification that " exception for gradation" while ASTM C33 should be followed? so, how is the gradation of aggregates and how to optimize the gradation?

Any input would be greatly appreciated.

 

[blake989]

I have never done a mix design for cast stone, however I do know that the mix is referred to as an earth-moist zero slump mix. That does not even come close to a pourable mix description for precast concrete. The method for design may be the similar, but I bet the water-cement ratio is just slightly different.

 

[epr]

The fine line between cast stone and architectural precast concrete has become blurred with the advent of veneer and cavity wall construction. The only difference in many cases is the size of the component. It is becoming accepted that cast stone is small enough to be installed by man-handling and small portable hoists, etc., while architectural precast concrete comprises larger units that require lifting and erection equipment, such as cranes, etc. Cast stone is usually anchored with metal strap anchors or dowels set in mortar or sealant, or dry anchors similar to those used for anchoring natural stone. The larger architectural precast concrete units are usually anchored with threaded inserts and metal fabrications. Because of these differences, in union areas it can also mean the difference between ironworkers or masons.

Since you are doing research, I suggest you begin with the PCI publication entitled "Architectural Precast Concrete" (I have the second edition, in which cast stone is addressed in section 3.5.15).

You should also log onto the Cast Stone Institute's website

http://www.caststone.org

to download their standard specification, which will answer a lot of your questions.

Now to your original question . . .

Cast stone is manufactured using a wet mix or a dry-tamping process. Very few fabricators (in the USA) use the dry-tamping process anymore because of the additional manual labor involved.

Differing requirements for absorption and compressive strength may be specified on a per project basis, but they need not be different for architectural precast concrete. The wet-mix process for cast stone is virtually identical to the casting of architectural cast stone, and therefore the concrete mix design can very well be the same.

 

[jheidt2543]

Just a comment. My intuition is that Cast Stone is a "non-structural" material to be treated like real stone or other veneer masonry. Archtitectural Precast is usually, but not always, structural, ie is supports other elements than its' own weight. Mix design in both is subject to whim of architectural design for color and finish.

Just my way of looking at it. For mix information I would call PCA and PCI.