Central Mixed Migration
- Published: Friday, 17 August 2012 18:03
- Written by CP Staff
Twin shaft technology equips Illinois’ Quad-County Ready Mix for DOT, RCC work
By Don Marsh
Recent delivery of central mixed concrete for Illinois Department of Transportation work from equipment other than a conventional tilt drum came not from the state’s major producers, who blanket the Chicago market, but a mid-sized, family-owned operator marking 60 years in business.
To meet production peaks for the final two phases of a three-year, 105,000-yd. IDOT contract, Quad-County Ready Mix Corp. built a “wet” alley at its 30-year-old transit mixed plant in Mt. Vernon. The producer opted for a BHS twin shaft mixer, which enabled a narrower alley and simpler material handling reconfiguration than a tilting drum. Located just over a mile from the Quad-County plant, the contract entails widening Interstate 57, from two to three lanes, near the Interstate 64 junction—about midpoint between Chicago and Memphis.
“Key IDOT officials visited prior to the 2012 construction start since they had not seen a twin shaft mixer first hand,” says Quad-County RM Operations Manager Neil Hustedde. “The main phases of the I-57 widening require 150 yards an hour for the paving train, a volume we couldn’t match very well with mixer trucks.”
Mixers were sufficient for the first phase in 2011, totaling 15,000 yd. At three times that quantity, this year’s second phase has seen Quad-County deploy the twin shaft mixer on two-load cycles, along with the dump trucks of sister operation, Clinton County Materials Corp., to meet the volume target of E.T. Simonds Construction. (Based in Carbondale, Ill., the contractor is accustomed to measuring plant and truck productivity through its own local business, Illini Ready Mix.)
With the robust motion of intertwined paddles along two horizontal shafts, the mixer is capable of turning out 5- to 5.5-yd. loads every 60 seconds. “The new plant equipment gives us capability for current and future IDOT pavement work,” says Hustedde, adding that the twin shaft equipment’s aggressive mixing capability will give Quad-County a chance to pursue some roller-compacted concrete (RCC) jobs.
Engineers on public and private work in Illinois are taking note of how their peers in neighboring Indiana and other states have embraced RCC as an economical alternative to asphalt pavement, prices of which remain unstable due to petroleum market volatility. So far, Quad-County RM has only tested RCC mix production in mixer trucks, but noted the material’s performance potential in pavements.
In Quad-County RM’s 60-year history, the Interstate 57 widening contract is second only in volume to a 2007–2012 project, the Prairie State Energy Campus in Washington County, Ill. (note page 27). A 1,600 MW generating station integrated with a 7 million ton per year Peabody Energy coal mine, the campus consumed 260,000 yd., including 4,800-yd. contractor Bechtel Corp. required on a peak day.
Prairie State was a fitting milestone for a producer that had last set a single-contract watermark in 1974—a coal mine structure consuming 40,000 yd. Operating under the original company name, Clinton County Ready Mix also saw its first expansion in 1974 with the opening of a plant in Okawville, Ill., now the home office. Over the next 18 years, Clinton County RM established a hauling business, Clinton County Materials; built three more ready mixed plants; and acquired Centralia Ready Mix, extending company presence to four counties. The business was renamed Quad-County Ready Mix in 1992.
From there, the company built four more plants and acquired Carlyle Ready Mix, Building Products/Concrete Division and Tri-City Ready Mix, bringing it into six counties. With 12 ready mixed plants, Quad-County RM and Clinton County Materials serve a 100-mile market radius. Their combined fleet spans 90 mixer trucks, 45 tractor-trailers, 30 tandem dumps and nine cement tankers. Quad-County RM also offers placing services via three pump trucks, concrete truck-mounted conveyors and a Telebelt conveyor. Present payroll is 125.
Fifty-five-year company veteran Herb Hustedde, grandson of Clinton County RM cofounder Henry Hustedde, is president of the two businesses; his wife Carol is in her 36th year overseeing accounting and office management. With more than 40 years combined at the family business, sons Neil and Kent split plant management and quality control duties, running a testing lab at their Salem, Ill., ready mixed plant. Both hold (ACI-equivalent) Illinois DOT Portland Cement Concrete Level III certification, and conduct in-house seminars on concrete technology as part of mandatory training for plant staff and drivers. (A third son, Chad, has progressed in the Cemex USA management ranks, starting in Florida and proceeding to Arizona, where he is Vice President/General Manager–Phoenix Area.)
“We have grown to a scale where we can move people and equipment around to supply large contracts requiring high volumes in short windows,” says Herb Hustedde. “After looking at opportunities and future growth possibilities, we can see expanding to other locations surrounding our current ready mixed plants.”
Dry to Wet Conversion
Compared to the installation of a tilting drum model, the BHS DKXS4.5 twin shaft mixer helps minimize the footprint of a new central mixed alley at Quad-County RM’s Mt. Vernon plant. The high-intensity mixer bears on an R&S/Loadcraft structure Cummings McGowan & West delivered for the plant upgrade. The St. Louis-based concrete plant specialist had to contend with integrating the BHS equipment and a two-silo Ross model built in 1980, and creating a new alley locked in by existing boundaries, truck routing lanes, and a buried fuel tank that could not be moved.
An existing cement batcher was shifted to the new structure while holding hoppers were placed above the new mixer. A new aggregate conveyor was installed at 20 degrees and extended further out from an old drive-through lane. This additional conveyor elevation allowed for a 6-yd. aggregate holding hopper. Once the materials are transferred from the aggregate scale below, to the holding hopper, the next batch can be weighed. Once the holding hopper is emptied and all materials are gravity discharged into the twin shaft mixer, the aggregate scale can discharge and transfer the materials immediately—equating to zero time wasted during the batching sequence. The new alley construction also saw the relocation of an existing cement scale and extension of powder augers.
Aggregate, cement and water holding hoppers, charged as the prior batch is mixing, unload into the BHS in 10 seconds. The mixer easily matches production pace and quality targets typically required for Illinois DOT projects, while positioning Quad-County RM to produce roller compacted mixes as the state’s RCC pavement market develops.
The BHS DKXS 4.5 is a 6-yd. (4.5 m³) compulsory mixer, netting a 95 percent homogenous mix in as little as 30 seconds. The mixing shaft is hexagonal, allowing a 60 degree placement of the mixing arms to produce a more intense mixing action and achieve higher quality concrete. The DKXS model’s worm gear drive system, exclusive to BHS, means less moving parts and friction and no oil cooler requirement. The mixer is lined with the manufacturer’s 1-in.-thick Optilong tile, placed in maximum, medium and normal hardness levels from base to top, respectively.
The mixer uses a rotary discharge gate of heavy-duty cast iron construction versus fabricated plate steel, with four proximity switches to control discharge. It has adjustable ledges for sealing, offsetting wear that compromises gap tolerances and leads to steel replacement. A robust and reliable shaft seal design features an automatic greaser, operating on 144-second intervals, or a total of 12 minutes per eight hours of production.
The twin shaft mixer minimizes central dust collection requirements: Its aggregate inlet area is sufficient for air displacement; between the intense mixing action and aggregate entering the mixer, cement dust is virtually encapsulated.