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Equipment manufacturers rise to RCC pavement mix production challenges.

The National Ready Mixed Concrete Association opened its 2013 education series with a webinar, "RCC: Your Third Pavement Choice," a fitting theme timed with the continued emergence of roller compacted concrete as a strong competitor to asphalt pavement. Ready mixed producers are responding to market opportunities by staging RCC pavement demonstrations and equipping plants for high output of the low slump mixes RCC projects require. Equipment manufacturers have tailored portable models, often combining conveyors and high-energy mixers, that can be charged in transit mixed plant alleys and load dump trucks at a pace matching contractor demands. Concrete Products surveys manufacturers' RCC mix-geared offerings here.


The Portable RCC Mixer combines a trailerized conveyor and platform from Stephens and MA0-6000 6-yd. twin shaft mixer from Sicoma North America. The mixer height is placed 13 ft. 4 in. to allow loading from conventional ready mixed plant. The conveyor extends so that mixer load point and belt discharge point are just under 60 ft. A truck collection hopper for loading mixers can easily be removed to load dump trucks. A motor control center is shipped with starters and controls for the conveyor and mixer, which are pre-wired to starters in liquid-tight metallic flux conduit. The trailer includes three 20,000-lb. single-axle transportation systems, With air brakes, turning signals and fifth wheel.--Stephens Mfg., 270/487-5774,; Sicoma NA, 727/934-4424,


Loadcraft Industries has integrated R&S Industries' transit and central mixed plant equipment into its portfolio of production and delivery equipment for construction materials and energy resources interests. R&S has teamed With BHS-Sonthofen U.S./Mixing Division on a roller compacted concrete mix-grade portable plant. The DKX 4.5-6.0 mobile mixer, which is designed to convert existing dry batch concrete plants into a RCC-capable central mix plant, is used for "low slump" roller compacted concrete at a moment's notice. It can be moved quickly and easily from one dry batch to another and meet market demands.

The model features a Loadcraft/R&S-engineered trailer and platform, plus BHS twin shaft mixer. It also features a 42-in. standard conveyor with dual 30-hp drives, hydraulic self-erection, and hydraulic leveling jacks.--Loadcraft/R&S, 325/597-2911,; BHS-Sonthofen U.S., 704/814-7671,


The company cites the largest portable roller compacted concrete mixer on the market, with Concrete Plant Manufacturers Bureau (CPMB) 10-yd. rated capacity for 1 in. and higher slump material, and 8-yd. yield for zero to 1-in. slump mixes.

The horizontal mixer is equal to all ranges of concrete mixes, including RCC and cement-treated base, and has been deployed on federal, state and Corps of Engineers projects. It is CPMB-rated for a 30-second mix time on 4- to 6-in. slump mixes for general use, and 4-in. or lower slump material in paving applications.

In most cases, the trailer-mounted horizontal mixer can convert portable or stationary dry batch plants to central mixed, and load Agitor or a wide range of dump tracks, or--with an optional dump cone assembly--front discharge, conventional rear or booster axle mixer trucks. Another optional component, a portable, 48-in. wet belt (bottom image, right), can be added for additional charging height and speed.

The horizontal mixer can theoretically produce up to 400 yd./hour of standard concrete and 300 yd./hour of RCC or CTB mixes. Delivered pre-wired, pre-plumbed and tested, it meets all NEC and NEMA requirements, and is UL listed with certified electrical panel. HM 4.5 yd. and HM 8 yd. mixer models in standard configuration are also available.--800/354-3238;


The twin-shaft mixer from the company's Concrete Products Group, combined with a range of portable and fixed plant models, quickly incorporates materials into a consistent, uniform mix. Material enters through the water and admixture curtain and is then mixed using the Astec paddle design to achieve a uniform blend and drive material across and down the mixer.

Intense shearing action delivers a uniform concrete mix for short production cycles. The finished material then exits the mixer and a proprietary automated wash-down system utilizes pre-positioned nozzles inside the mixing chamber to thoroughly wash down the interior, allowing all materials to be flushed through the discharge gate. The wash-down can be activated manually or automatically.--Astec Concrete Products Group, 423/827-1227;


Company has recently added the Jumper series mobile plants to a full range of concrete machinery offerings. With Jumper 750, 2500 and D1 models, the new series is configured for easy transport on standard trailers or 40-ft. open top containers, and site installation without foundations. The Jumper 2500 is equipped with a Simem MS02500 twin shaft mixer, with a compacted concrete output of 1.7 cu. m per batch. The aggregate section has a storage capacity of 20 cu. m (50 cu. m optional) and can be divided in 2, 3 or 4 compartments. A cement scale and a water scale are also included. The plant can be supplied with wheels for road transport.--210/581-8600;


The Mobile Mixer is configured to be driven under the outlet of any dry ready mixed plant to convert it to full central or paving operation. The high-efficiency twin shaft mixer, one of Ocmer's flagship products, is already said to have excellent reliability and ruggedness as well as the ability to mix thoroughly, thereby offering a saving on cement for equal strength product, compared with older styles of mixer. In operation, the dry plant discharges aggregates, cement and water into the mixer, together with admixtures. Once mixed, the truck is charged through the on-board conveyor. A choice of mixer sizes nets production of 150 to 250 yd. per hour.

Once on-site, setup includes folding down the walkways and stairs, connecting power to the motor control panel and connecting the actuators to the control system. If the existing control system cannot handle a mixer, a separate controller for mixing is available. Scale-Tron represents Ocmer in North America. Scale-Tron represents Ocmer in North America.--800/632-7083;


Company specializes in the design and manufacture of continuous mobile mixing plants for the concrete, environmental and construction industries. With over 25 years of continuous mixing experience incorporated into its design, the Rapid Mix 400 and 600C models were developed to be a cost-effective method for mixing a wide range of materials for such applications as: roller compacted concrete (RCC), for pavement or dams; cement treated base (CTB), or cement stabilized base; Bentonite enriched soils for lagoons, waste landfills and protective cell linings; and, flowable fill.

A large mixing chamber coupled with twin shafts rotating at 110 rpm ensures a homogenous mix on a consistent basis of 400 yd. and 600 yd. per hour, respectively. The Rapid Mix 400 and 600C are completely mobile, and self-contained with an on-board diesel engine and generator. Both models can be set-up, erected and calibrated usually in about four to six hours. Additionally, these machines are electrically driven with the exception of the hydraulic system used for set-up and erection of the plants.--303/853-0068;


With an eye toward roller compacted concrete (RCC) and other specialty mix production, the company offers a solution to combine the simplicity of dry-batch plants with the superior mixing quality of a twin shaft mixer. The mixer is installed on a mobile trailer unit. The dry-mix plant is feeding material into the mixer. A standard recipe requires only 30 second mixing time. Mixed concrete is discharged onto a concrete discharge belt, which loads directly into a dump or mixer truck. No special modifications are required to the dry-mix plant.

The mobile twin shaft mixer is a self-contained unit and an essential option if high-quality mixed concrete is required. An existing dry batch plant can easily be upgraded and converted to a wet mix plant. The plant can now produce high quality concrete mixes such as RCC, cement treated base self consolidating concrete, zero slump concrete, etc. More flexibility and variability increases the application possibility of the plant and generates more revenue.--866/879-6312;

Retarder suits specs for 700,000-yd. RCC dam

Phased construction at the City of San Diego's San Vicente Dam, elevating it from 220 ft. to 347 ft. high and expanding the structure's footprint to increase reservoir capacity from 90,000 to 152,000 acre feet, continues through 2014.

A five-year master plan encompasses a 2010-2013 placement schedule for nearly 700,000 yd. of roller compacted concrete mixes--primarily by an advanced system of high speed conveyors and shoots. Due to the aggressive timetable, the dry mixes have been placed in varying weather conditions, including summer temperatures exceeding 110[degrees]F, accompanied by low humidity and occasional high winds.

Excessive RCC surface drying has been a concern because of the potential for improper bonding between 24-in. lifts. To maintain mix characteristics necessary for required concrete bond, 18- to 24-hour initial set and 26- to 45-hour final set, engineers approved a molasses-based, set-retarding admixture: Sika Plastiment ES, dosed at 17 oz. per weight of cement. In a mix with 240 lb. of fly ash and 180 lb. of portland cement, the Plastiment ES has helped maintain typical 20-hour initial and 39-hour final set times.

With production rates averaging over 2,000 yd./day, back up dispensing systems were put in place to assure continuous admixture supply in case of system breakdown. Sika provided around-the-dock technical, maintenance and calibration service for the San Vicente Dam Project.--Sika Corp., 800/933 7452;
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Publication:Concrete Products
Date:Feb 1, 2013
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