During his World of Asphalt 2024 presentation on asphalt plant efficiency, Astec’s Greg Renegar shared ways you can turn your storage silo into a game-changer. By filling the silo at the end of the day, you’re ready for FOB customers first thing in the morning when other plants might be experiencing start-up woes. But Renegar and others cautioned producers on some of the reasons you might not want to take advantage of this business practice.
The Mix You Offer
Lack of planning on your customer’s part could result in wasted mix for you! There’s no point in producing 100 tons of state mix at 300°F if your first five customers show up wanting something less pricy at 340°F. Where’s the fellow who wanted the state mix? You want to make sure the right customer is in the right lane for the right mix.
Heat
Speaking of temperature, make sure you have heating systems in place to store mix overnight. If you don’t have proper heating systems in place, you run the risk of losing temperature and creating a solid problem. There are companies making electric heating elements that can be placed in silo cone packages to take the fear out of overnight storage. These entities might not make the silo itself but are experts in the manufacture of electric heating components and provide these to the OEMs who make the silo and cone.
Drain Down
Even with the concern of temperature under control, you want to consider the mix design itself. Experts in the field share concerns about storing open-graded mixes due to a phenomenon known as drain down. This is when gravity pulls the liquid asphalt cement (AC) away from the aggregate and down toward the silo cone.
Steve Jackson, the vice president of plant operations and sustainability for NB West Contracting, Pacific, Missouri, spoke of this in stone matrix asphalt (SMA) mixes. “The worst mix that I have seen for drain down is SMA,” he shared. “That is why some agencies are reluctant to remove the cellulose fibers even when you add ground tire rubber or reduce the mix temperature.”
Jackson offered examples of working with and around this problem in the June article “How to be the Plant Everyone Buys From.” His experience offers hope for adjusting the gap-graded mix so it can be stored overnight for quick loadout in the morning, if you’re willing to work with it.
For producers looking to optimize the use of the storage silos, it’s possible to adjust the mix design and temperature to ensure you have exactly what your customers are looking for first thing in the morning while avoiding the worry of drain down.