|Astec Concrete-Plant Technology|
The new Big Name in concrete plants: portable, versatile, and dependable quality.
Even those industry professionals who are very familiar with Astec's reputation for designing state-of-the-art HMA technology may not realize that the company has more than 20 years of experience with building concrete production facilities.
The contractors present at that demonstration observed the ease of mixing in the Astec Twin Shaft Mixer, the consistent flow of fractionated aggregates, and the precise water control.
Everyone agreed that a new era of concrete-production history was unfolding before their eyes.
Astec has been putting its 20 years of experience building concrete plants to work for the industry. Many believe that the technology provided in the Astec Continuous Blending Concrete plant represents the first real innovations that the concrete industry has seen in decades.
A solid history
Most industry professionals probably think they know Astec, Inc. very well, but some may not be entirely familiar with its history of manufacturing production equipment for concrete. In fact, that history goes back more than two decades.
In 1987, the first pervious concrete ever produced in the United States came out of an Astec plant. That material was used to pave a 14-acre (5.7-hectare) parking lot at Epcot Center in Disney World, Florida. That same plant was later used to provide roller-compacted concrete (RCC) for the expansion of the Port of Los Angeles in California.
Another concrete plant manufactured by Astec was one of two plants used to produce RCC for the Penn Forest Dam in Bethlehem, Pennsylvania. This project—the third largest dam in the United States built with RCC—consisted of 360,000 yd3 (301,006 m3) of RCC. The plant operated reliably through two shifts a day, six days a week.
In late 2008, Astec announced that it was forming its Concrete Products Group, a move that only solidified the company's status as a leader in concrete innovations.
One concrete producer in the southeastern United States who recently took delivery on a new Astec Continuous Blending Concrete plant commented on his initial impression of the technology that Astec had designed.
"As I listened to you explain what was happening in your new plant I thought I might be witnessing a revolution in concrete production equal to the change from hand to mechanical mixing," he said.
This producer has his own solid history in the industry. He was involved in one of the first public RCC projects undertaken by the United States Army Corps of Engineers, the Lake Nickajack Lock and Dam on the Tennessee River. He has been involved in RCC since the late 1980s, and has been active in the industry right up to current projects such as the new Volkswagen auto plant in Chattanooga, Tennessee. Now, he has a new Astec concrete plant on his yard.
This new plant—dubbed the Universal plant because it makes the whole range of concrete mixes—uses a powerful, 250-hp Astec Twin Shaft Mixer. It includes a transit truck chute and boot in addition to a larger surge hopper, which proves popular with the contractor's customers who haul concrete in dump trucks for slip-forming and RCC paving.
The heart of the plant's state-ofthe- art technology is the switch it makes from conventional aggregate batchers to continuous volumetric aggregate sections with live gates and calibrated bins. And if the bins look a little like cold feeds from a hot-mix asphalt plant, don't be surprised. Astec Industries' Chairman and Chief Executive Officer Dr. J. Don Brock had a vision that Astec concrete plants would be advanced, yet use field-proven components from the production facilities manufactured by Astec, Inc. So, for example, a feature such as the surge hopper on a self-erecting frame can be easily compared to its cousin on the Astec Six Pack SEB 100-ton (91- tonne) surge bin for HMA.
In fact, the whole concept of a super-portable, self-erecting, continuous concrete plant is linked to the successful Astec Six Pack portable HMA production facility. And these concrete plants borrow the field-proven performance of the Astec Computer Control Systems that give daily assurance of quality material mixes to paving contractors around the world.
The new Astec Total Concrete Control system (CTC3) gives the operator smooth control over the powerful Astec plants. Available in packages that can handle three sizes of Astec Twin Shaft Mixers—a 125 hp, a 200 hp, and a 250 hp—the CTC3 system manages precision aggregate flow from each of multiple bins and distributes cementitious materials from silos. And Astec incorporates a breakthrough water system using Coriolis effect water-flow meters. Since the water system controls flow continuously, the accuracy is a real-time 9 oz (266 mL) of water per yard.
The incorporation of these cutting- edge Astec features provides a way for contractors to use Optimized-Gradation Mixes, allowing them to give customers concrete mixes that are consistent and that have the workability needed for quality placements.
Because the Astec plant can accommodate six or more aggregate bins, the contractor can use designs that have four or more coarse aggregate sizes and two kinds of sand. This versatility provides accurate volumes of exact gradations so the correct amount of cement paste will provide the target strength needed for the specified design.
Industry professionals who have taken a closer look at this latest Astec technology agree:
Never before has this level of precise control been available to concrete producers.
This article originally appeared in Hot-Mix Magazine Vol. 15 num. 1