Use and results
After fabrication of the mixer platform, installation only took a few days. The plant was then fully commissioned and mix designs tested. “The new automated controls were easy to learn and straightforward,” Daigle says. “Our old mixer was completely manual, so it’s far less labor-intensive to run our new batch plant.”
The precaster’s most immediate and profound improvement was the speed with which it was able to achieve or exceed design strength. Elm Street’s target for burial vaults is 4000 psi or greater in 28 days. After the plant improvements, it were hitting 6000-7000 psi within seven days—and with up to 200 pounds less cement per yard.
“The mix intensity and batching accuracy that our new plant provides is delivering significant benefits,” says Daigle. The savings in cement gives Elm Street greater flexibility in a competitive market, enabling the producer to reduce production costs, enhance product quality, and achieve a greater profit.
The early strength provided by the new system also enables the firm to strip forms up to five hours sooner than before. This not only helps avoid breakage, but allows the company to double-pour when necessary and apply finishing touches to vault covers and other components sooner than ever.
“Often with our old mixer, I would come back after dinner or after hours to strip forms and apply finishes,” Daigle says. “That gets old fast. Now, we can easily get our work done in a normal shift and the finished product looks much better.” The new mixer has eliminated bugholes and other cosmetic defects.
Improved mix quality also allows Elm Street Vault to use structural fiber in place of wire mesh for secondary reinforcement in many applications, including vaults and manholes. This provides savings in labor, set-up time, and materials.
Elm Street Vault plans to soon begin testing self-consolidating concrete (SCC) mix designs, which was not possible with its previous volumetric mixer. “SCC is definitely something we want to start producing,” Daigle says. “Most of the precasters I know are pouring SCC. With our ACT/Wiggert batching system, SCC is not only something we believe we can produce, but will also provide new opportunities for us.”
Hank Giles is an independent journalist who writes for industrial trade journals. Please visit www.concretebiz.com for more information on Advanced Concrete Technologies.
Elm Street Vault’s modernization in the summer 2012 included the following components:
- New ACT/Wiggert HPGM 750 high-shear planetary counter-current mixer, capable of producing up to 0.6 cubic yard per batch in approximately 30 seconds. Equipped with integrated cement weigh batcher for increased precision batching.
- New ACT SmartTouch Controls with automated batching, one-touch call station control, visual touch screen for commands and indicators, batching history, and recipe storage.
- New mixer platform fabricated locally according to ACT drawings.
- Reused single cement silo and screw conveyor.
- Reused dual aggregate bins. Converted to decumulative weighing with the addition of load cells.
- Enclosed aggregate bins to shield them from the weather and provide improved batching.
- Reused overhead crane and crane buckets for concrete distribution.