Писах няколко е-мейла тук и там. Вижте един от отговорите:
"... As a general rule, the maximum size of aggregate (regardless of the type) should be kept to less than 1/5 of the finished element size. Therefore, in your case, with a 1 inch member size, the maximum aggregate should be less than or equal to 1.5 inch (about 5 mm).

Unfortunately, unique concrete mix designs such as these are often accomplished through trial and error. (Mix a batch and test it. Change the proportions of materials and retest. Continue retesting new mixes until an 'optimum' mix is achieved for the given set of materials.)

As a starting point, I would likely start with an aggregate gradation that had equal distribution of aggregate particle size from 5 mm down to very small sand (i.e., 0.2 mm or so) at one of the proportions you noted below using conventional sand and gravel. Then mix additional batches substituting in the marble dust for some of the conventional aggregate and see if there is any impact on the resulting compressive strength of the concrete.

Hope this helps. Let me know if there are any others questions I can help with. ..."

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