Since the Panama Canal opened in 1914, shipping capabilities and ship sizes have grown. As a result, many modern vessels are now too large to fit through the famous waterway. In 2009, a consortium of international companies called Grupo Unidos por el Canal (GUPC), was awarded the contract to expand the canal's capacity with a third set of locks.

The project involves excavating several million cubic yards of earth and rock and producing more than 5 million cubic yards of concrete to form the new locks and water recycling basins. Work is scheduled for completion by fall 2014, in time for the canal's 100th anniversary. This means the concrete must be poured within about 30 months.

Simem SPA, of Minerbe, Italy, has supplied two twin-shaft concrete batching and mixing plants for the job; one in Panama City and another in Colon. Each plant can produce 942 yards per hour, with a cycle time of 80 seconds per mixer. The plants' computer-based control systems will simplify installation, and climate-controlled electrical panels are designed to ensure problem-free operation.

U.S. subsidiary Simem America Corp. began installing the plants in June 2010, and the Panama City plant produced its first batch of concrete in November. Regular production was scheduled to begin in February, and gradually increase to full capacity by March or April.

Design and production

Many factors were considered in designing the concrete plants, such as raw material requirements, output capacity, and concrete placing temperature. In the end, the layout was based on a shared aggregate section serving two independent mixing towers. Each contains two MSO6000-HLS twin-shaft mixers with an output capacity of 6 cubic yards of compacted concrete per batch.

Five different aggregates will be used: three grades of stone and two types of sand. Each plant's control system sends continuous consumption information to the aggregate loading system, which loads the bins with different aggregates as required.

Due to the required concrete placing temperature of 50° F in an area with a typical ambient temperature of 95° F and higher, cooling is a priority. The aggregate is cooled while it is loaded into 980-cubic-yard capacity bins, which are enclosed with insulated panels. Cold air is blown into the enclosure and directly into some bins to control the aggregate temperature.

To maintain a cycle time of 80 seconds, each mixing tower uses five scales, one for each type of aggregate. The aggregate is transported from the scales on a high-capacity extraction belt and an inclined belt before being diverted into holding hoppers above each mixer. The mixing towers each use a double set of ice scales, which discharge ice onto the inclined aggregate belt conveyor.

One type of cement and one type pozzolan will be used in the canal's mix designs. Each mixer has two 150-cubic-yard cement silos and two cement scales—one for cement and one for pozzolan. Three types of admixtures will be used, and dosed by one double-chamber and one single-chamber scale.

The plants are equipped to use clean, chilled water or slurry water. Slurry water will be supplied by Simem's Betonwash 25 concrete reclaimers. Water is dosed with two scale units to ensure accuracy.

To further control consistency, the plants use a mixer moisture probe combined with power consumption readings. Rather than calculating the amount of water required, the moisture probe verifies the moisture level in the mix as a point of reference.

Most of the concrete produced for the canal will be loaded into open-bed agitator trucks with a capacity of 11.7 cubic yards, making it necessary to double-batch to fill the truck. To reach the required capacity, each mixer is equipped with a holding hopper that can hold one batch, thus ensuring that the truck movement will not delay mixer discharge. The plant is also equipped with an automated, moveable chute for loading traditional ready-mix trucks.

Erik Johansen is director sales & marketing for SIMEM America Corp.

Mobile batch plant

The company's new portable concrete batch plant produces up to 78 cu. yds./hr. Two aggregate batchers can handle 5 and 7 cu. yds./hr. The cement batcher processes 5 cu. yds./hr., with an 8-in. screw discharge and 24-in. conveyor belt. The plant is easy to move and set up without a crane. A three-compartment aggregate bin and single aggregate batcher are optional. Odisa Concrete Equipment. +52-55-54263342.

High-output central mix plant

The LO-PRO 427 central mix batch plant is available with a 48-in.-wide charging belt. When combined with a tilt mixer, the plant can produce up to 350 cu. yds./hr. Features include a LO-PRO blending cement batcher; 50-, 70-, or 90-cu. yd. aggregate storage bins; and standard 427-barrel single-compartment cement silo. It can be configured for dump truck or transit mixer charging. Con-E-Co. 402-426-4181.

Reduce cost and waste

The high-performance SmartMix Plant is designed to reduce material and energy costs and improve productivity. Its high-shear planetary mixer minimizes cement usage and efficient motor requires less power to operate. The plant can reduce waste with automatic end-of-day mixer cleaning and a dust collection system. Available with 10- to 40-cu.-yd./hr. capacities. Advanced Concrete Technologies Inc. 603-431-5661.

Meet onsite demands

The MCM OnSite Plant is a portable, automated concrete batching plant that can produce up to 60 cu. yds./hr. It is easily assembled with pinned connections, pre-plumbed air and hydraulic hoses, and pre-wired plug-in electrical connections. The main structure is composed of two 8 x 40-ft. units built to meet sea container specifications for easy transportation. MCT Supply Inc. 877-628-4768.

Produce more, spend less

The Model 275 concrete batch plant can be moved as a single unit and set up in less than an hour. It comes standard with a self-erecting, 58-ton cement silo, and can be configured with two, three, or four aggregate bins. The plant's small footprint allows maximum flexibility in tight quarters. Cemco Inc. 855-564-5855.

High capacity, small footprint

With a high-capacity vertical silo, the compact Bandit B12 MVR ready-mix concrete plant offers more site selection options. The standard design Bandit B12 MVR ships in five loads, and is pre-wired, plumbed, and tested for fast setup. Configured to meet the exact needs of the concrete operation, the plant can produce up to 200 cu. yds./hr. Terex Roadbuilding. 405-787-6020.

Hand-loaded batch plant

Low-tech construction teams can produce consistent concrete with the Concrete MD hand-loaded batching mixer. The mixer uses measured batching buckets for sand and gravel for the same recipe time after time. Measured buckets of water and bags of cement are broken into the center of the mixer as the dual-rotation auger blends .65 cu. yds. (.5 meters) every 15 minutes. Cart-Away Concrete Systems Inc. 800-909-9809.

Portable and dependable

Compact Easy portable concrete batch plants are self-contained for ease of transportation without specialized equipment. Each is completely assembled and wired for automated control, batching, conveying, and mixing. A fully enclosed operator cabin has a control board for manually operating the plant, with digital indicators for weigh batchers and a PLC/PC-based automatic control system. CIFA USA Inc. 877-243-2345.

Twin-shaft mixers

MSO6000-HLS twin-shaft mixers have an output capacity of 6 cu. yds. of compacted concrete per batch. Each has two 150-cu.-yd. cement silos and aggregate bins with a storage capacity of 981 cu. yds. The mixers have a fully automatic high-pressure cleaning system to ensure quick and easy clean-up. Simem America Corp. 877-333-9924.

Practical for many markets

The Mobilmix 0.5 mobile mixing plant has an output rate of up to 40 cu. yds./hr. With two completely preassembled and pre-wired, 20-ft. containers, the plant is erected and ready for operation in a matter of hours; no crane is required. The pocket-type aggregate bin can store up to 21 cu. yds. of material. Liebherr Concrete Technology Co. 866-879-6312.

Mobile and modular

EG-10 and EG-10MX mobile batch plants can be used for temporary installations, special projects, or in permanent facilities. Setup is quick and easy; no foundation or erection is required. Both models feature four-compartment aggregate bins with 110-ton capacity, and cement bins with 60-ton capacity. BMH Systems. 450-449-4770.

Modular plant design

The ULC-IV ready-mix batch plant's modular design allows producers to customize a plant for today's needs and still expand in the future. All kits mount to the batch plant at the same elevation as the cement batcher for simple installation and easy maintenance access. Modular bolt-on kits facilitate installation and minimize downtime. Besser Co. 800-968-0444.

Load front or rear discharge trucks

The Mobile 12 SE, available in central and transit mix configurations, requires no concrete slab or steel plating in most locations. The portable plant can be set up in 20 minutes by one person without a crane. Two 150-barrel silos feed a 12-cu.-yd. cement batcher, and two aggregate batchers have 10- and 11.5-cu.-yd. capacities. Larger capacity storage bins are available. RexCon LLC. 414-351-7000.

Portable plant for large jobs

The large, portable Falcon plant's standard frame can support two 1000-barrel cement silos and 200-ton aggregate bins. An optional frame can hold up to 400 tons of aggregates. The plant can be designed with a 36-in. belt, water batcher, and holding tank, for a 200-cu.-yd./hr. production capacity. The central dust collector can be mounted to save space. Stephens Mfg. Co. 877-626-0200.