Modular Docks’ Aquatic Feat

While floating massive concrete structures requires no magical intervention, it does demand ingenious design. Accordingly, the patented Uni-Module invented

While floating massive concrete structures requires no magical intervention, it does demand ingenious design. Accordingly, the patented Uni-Module invented by Jerry Mattson of Lake Ozark, Mo., functions as buoyant concrete block that can be used to assemble a variety of aquatic structures, including residential docks, commercial marinas, and wave breaks.

Modular Concrete Docks, LLC fabricates the units at its Eldon, Mo., plant and transports them by flat-bed truck to marina docking sites. For convenient hauling and handling, the patented Uni-Module is typically 4-ft. square and 3 ft. deep; it weighs in excess of 1,500 lb. and features a low center of gravity as well as a free board of 18 inches. A foam core encased by concrete on all six sides provides buoyancy. Produced in a Cemen-Tech SCD3-50 volumetric mixer, the shell concrete combines portland cement, Lafarge Max-Chem slag, sand, 5/16- to ?-in. pea rock, Re-rod and Forta Ferro structural fibers.

Precasting Uni-Module components entails the use of a form, core rods, and a form liner, plus exterior vibration. Each unit is finished with a permanent, textured, crushed-ice anti-skid surface. The process and materials, company representatives affirm, are designed to produce durable, low-maintenance, rugged modules for reliable, floating foundation assemblies.

Using an interlocking key way system to maintain alignment, Uni-Module components are joined with rods and post-tensioned cables to create a stable surface suitable for docks, breakwaters, swim decks, and fishing decks. The frame design, including passages spanning the width and length of each unit for connecting rods and cables, permits a variety of configurations and inclusion of custom docks or other elements. Any floating structure, the producer notes, can be individually designed and engineered to meet site-specific demands.

Supplying protection for boats, shorelines and swimmers, the final product is able to stop three- to four-foot waves. The stability of a 12-ft.-wide breakwater, for example, reduces wave energy from exposure to main waterway channels, while nondeteriorating and nonpolluting precast construction protects the natural environment. A 10-year warranty attests to a long life span.

Since the Uni-Module patent was issued in 2001, refinements to its design have improved the through-rod frame and post-tension cable systems, evident in the company’s standard 12 _ 80 breakwater comprising 60 modules. Each 4-ft.-square, 3-ft.-deep component weighing 1,450 lb. has 16 preformed channels to accommodate connecting rods through the unit. Coupling nuts and other threaded fasteners are used to secure and reinforce the system. Also included with each breakwater are seven 2,500-lb. concrete anchors with winch stands and eye guides; seven #11 marine winches with 250 ft. of galvanized cable per winch; and, four navigational amber lights on 2_-in.-square upright posts extending three feet above the deck. Weighing in at 115,000 lb. or 57.5 tons, single breakwaters can be joined by post tensioning to extend overall length.

Each structure is designed to meet or exceed multiple standards or codes promulgated by widely recognized professional bodies. Among these are the American Concrete Institute, American Society of Civil Engineers (Engineering Practice Manual No. 50), American Society for Testing and Materials (ASTM A-123 and ASTM-A36), and American National Standards Institute.

A recent project on Missouri’s Lake of the Ozarks was tailored to the demands of Bayou Bills, which required permanent, year-round boat docking for restaurant customers. Besides a wave attenuator, the docks include 15 slips measuring 20-ft. _ 28-ft. Wind from three directions, boat traffic producing waves 14 feet crest to crest, and continuous three- to four-foot waves were typical conditions for which the installation had to be designed. Equal to the challenge was a post-tensioning system incorporating large polyurethane couplers to provide flexibility and longevity amid constant wave incursion. The Bayou Bills structure was preassembled and pushed downriver to the restaurant location for installation. Today, the multi-slip dock and wave attenuator day docks provide a convenient boating platform as well as protection from main-channel water traffic that produces waves exceeding five feet.