Batching and Mixing

A recirculating high-shear vortex or impeller pump works well. For cement and water it is important to remember we are actually emulsifying the powder and water, dissolving the finest powder materials and creating a solution or paste--depending on the viscosity required. For very thick pastes, a pump is not reccommended, but rather a high-shear mixer should be utilized.

The best way to do this is to use a mid-range water reducing agent in the mix at the plant to establish an initial 100mm slump at the plant with the W/C slightly lower than specified. Then on site add a small amount of prescribed high-range water-reducing agent after dosing the small amount of yet-to-be-added water.

Leonard,

I apologize for the untimely reply. We have had technical difficulties here on the Q&A service.

Well, the pouring of concrete can certainly be completed in December in NC--even in a "normal" year! The main problem is the slower set time experienced at +34˚ to +60˚ F. At these cooler temperatures you will get the best results actually. However, more care is required.

Although my Q&A is concerning the mixing technology, I'll go ahead here and really oversimplify what is required. First do not pour the concrete too wet--just wet enough to make it workable and finishable. Be sure to rod the concrete well and compact it thoroughly. Use very little sprinkle water to finish, as at cooler temperatures the mix water will creep to the surface more slowly and mot evaporate nearly as fast. Finally--and most importantly--do not pour on frost, and blanket the firm green concrete if the temperature nears frost!