Dry Cast mix design

[gemotorres]

How much Air Content do I need to assume to design a Dry Cast mix for Reinforced Concrete Pipe?
Zero? or 2% in average? I am updating my mix designs that have a 27 cu.ft/ cu.yd yield but with 0% air, but the yield raise if I put air, and I should need to adjust and reduce the aggregates weight.

Some comments please.

 

[concretemasonry]

What type of "Dry cast"?'

Is it dry tamp, zero slump, very low slump or just low slump? Is there a required air content?

Much depends on the placing and vibration methods and the curing time in the forms. For the extremely dry mixes (first two listed above), the aggregate gradation AND particle shapes are very critical and water is the best ( and economical) way to achieve higher strength and and density. - For those very low/zero slump materials, you must forget about a tradition mix design, except for the chemistry (cement and pozzolans).

If this is for manufacturing, the CPI requires a high degree of record keeping on the materials and batches. A local person that has worked in that industry could be a great resource since very often a mix design must be adjusted for very slight material variations. - In a sophisticated plant it is more of a familiarity/experience issue and not a strict science since the production processes are extremely accurate and efficient and they can be fine tunes by slight adjustments if the gradation change by a percent or two.

Dick

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