Batching and Mixing

I do not know of real stone being used in tilt-up in this manner. However--in my experience, which is limited in this area--the use of lightweight cultured and area faux stone has been done, as well as face block and brick, both thinner to affect weight.

You are making very large cylinders that will allow you to use larger, stronger aggregate. Choose the largest crushed stones allowable for a 6" diameter test cylinder--which would be 2"-2¼" stones that are jagged. Don't use more than 60% of the total weight of the aggregates--in this size.

Next, use a blend of smaller crushed gravel from 5/8" down to sand that is at least 60% sand fines. We call this a graded blend of crushed stone and fines.

To this add the amount of cement required for teh strength you are wanting to make--10%, 20% or 30% of the weight of the aggregates.

Go to concrete.org and click on mix designs to read about the all important water/cement ratio. This ratio will allow you to glue crushed aggregates together weakly or strongly.

By "batching" time, I am assuming you are not asking about "mixing" time. Batching is normally measured in cycle time. A batch cycle incliudes the weighing of aggregates, cement, pozzolans and the metering or weighing of admixtures and water. This weigh-up time is variable dependent on whether you use a single, cumulative weighing hopper or individual hoppers allowing simultaneous weigh-up. The size of the dosing gates, feed rates of materials, etc. are all factors.

The mixing time in a "premix" plant, or "central" mix plant, is dependent on whether a complete, ready to test mix is desired, or a "shrink" or "starter" mix is being completed for dust control or quality control reasons (initial water/cement ratio control), i.e., limiting variables in numerous transit mixer drums.

The former is commonly referred to as "compacted" concrete, and to attain a good throroughly mixed compacted product it will depend on the type of premixer used. Low-intensity drum type mixers may require upwards of 120 seconds of mixing, while high-intensity mixers such as a twin-shaft mixers may require only 30 seconds for compacted results and as little as 5-10 seconds for shrink mixing.

The discharge time of the mixer is dependent on the type of truck receiving the mixture and that truck's ability to accept the mixture. The type of mix will also impact discharge times--whether mixes flow or not--and keeping in mind that higher cement content mix designs and lower slump mix designs discharge much slower.

Average cycle times for a normal 10 yd truck load can vary from an absolute minumum of 60 seconds up to 5 minutes depending on the aforementioned factors.

Purchase the pre-bagged product with the 3,000 psi formula-- for 2,000 bag product, you can add 20% more cement, but be careful not to add too much water as you will not have enough fines to balance the mix.

You will require a mix design by a local engineering firm familiar with your particular area, freeze-thaw, etc.

I assume you have also looked at RCC with fiber? Visit pca.org and concrete.org and look at the cost benefit of 80,000 sq. ft. of RCC placement vs. slump concrete with steel reinforcement.