Plumb concrete is normally accepted for massive concrete works in which stone pieces of larger sizes are added along-with normal concrete to achieve economy. The proportion of concrete with stones depends on may factors like size of member, availability of reinforcement, size and shape of stone , grade of concrete. Normally, proportion of concrete may be 30 to 60 % of total volume. Is there are standard norms or design procedure?
To answer this properly I may have to start with the function of concrete. Since you already know plumb concrete is used in foundations and not in structures it is evident enough that we don't have to worry about a lot of exterior conditions that may arise if the concrete was above the ground level.
So now going into foundation design, there are different types of foundation and plumb concrete cannot be used for single column footings or any foundations of smaller dimensions. I think you know this too.
Now, coming to your answer, when we use aggregate for concrete there are specific requirements for its size and strength so that we can achieve an overall strength (concrete is usually used to withstand compression). So the plan concrete design will depend largely upon material property of the aggregate (plumb) such as density and compressive strength.
All you need to do is find a material and it's properties and make some large enough test cubes with trial and error method.
I don't know a better way as of now because you are specifically wanting to know the mix design ratio.
- Plum consist of black trap basalt of minimum 100 Kg /cm2.
- The nominal concrete mix 1:4:8
- Maximum aggregate of size 25mm.
- The plum volume in concrete not more than 50% of total volume.
- Layer shall not exceed 900mm.
The nominal maximum size of coarse aggregate should be as large as possible within the limits specified but in no case greater than one-fourth of the minimum thickness of the member, provided that the concrete can be placed without difficulty so as to surround all reinforcement thoroughly and fill the comers of the form.
A mix design for plum concrete:
PPC Cement 53 Grade: 220 Kg
Water Cement ratio (w/c) : 0.6
Free Water: 132 liters
300 mm Metal: 666 kg
20 mm Aggregates: 666 Kg
10 mm Aggregates: 539 Kg
Fine Aggregate (Sand):1038 Kg
Admixture Dosage :0.6%
Admixture: 1.4 liter
The density of Concrete: 2596 Kg/cum
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