Precast Solutions - January/February 2008 - (Page 8)

YOU CAN'T DO THAT WITH CONCRETE – UNTIL NOW. With micro-reinforced concrete, precast concrete will become the material of choice for a wide range of applications that, until a short while ago, would have been unimaginable. For example, MRC makes it possible to transform precast elements into structures that are monolithic and water-resistant. Edges of the steel mats, left deliberately exposed during precasting, can be interwoven and mortared on site – much like a scarf joint during wood construction to create a seamless joint. Potential applications include roofs, foundation walls, water tanks, boats and other structures. Precast architectural panels will likely be the first significant application for MRC in North America. After that, precast building elements including floor and roof decks, stairs, balconies and shaft walls are distinct possibilities. Research has already begun toward making lightweight concrete pipe. Reducing the weight of precast modular buildings is also under investigation. For smaller-scale applications, its reduced weight and thinner profile should make MRC attractive for use in site amenities, countertops, plumbing fixtures, furniture and other architectural specialties. One of the construction industry’s top engineers, Charles Thornton, Ph.D., P.E., founder of the international engineering group Thornton Tomasetti, has evaluated MRC and is enthusiastic about the possibilities allowed by the material. “The material’s homogenous composition is more like a very high-strength wood with nearly equal tensile and compressive strengths. Or perhaps we should consider it to be like a ‘liquid steel’ that can be cast into whatever shape required. Either way, it is an exciting new material in the designer’s palette and may replace traditional building materials in many applications.” structural capacity and did not release fragment A closely spaced reinforcement mat made of multiple layers of fine-woven steel wire mesh gives MRC unusual flexural and tensile strength. projectiles. A number of European projects have utilized precast MRC blast resistance in both new construction and retrofit applications. Freestanding, blast-resistant walls protect a community center and a general consulate. The thin panels were also applied over the consulate’s existing facade. Using conventional reinforced concrete in this application would have required separate footings and would have been thick enough to block an existing driveway. Precast MRC panels can be used in conjunction with conventional concrete construction to create fragmentation protection slabs. For example, a highsecurity data center used standard concrete poured onto precast MRC panels to protect against an attack via the public lobby above. In another situation, precast MRC cylinders were used as stay-in-place forms for conventional concrete columns. In addition to imparting blast resistance, the cylinders avoided the expense of conventional formwork and reduced the amount of constraining reinforcement required in the column. Not surprisingly, MRC can provide protection for forces in combat. The U.S. Department of Defense has approved MRC panels to protect forward operating bases from fragmenting mortar rounds and other explosives. On the domestic front, MRC has been proposed for use as containers for waste receptacles in public areas to minimize the damage that could result from a bomb hidden within. The material’s strength, ductility and reduced structural mass can provide similar benefits in seismically active zones. In Turkey, for example, existing columns in an industrial building were wrapped with MRC to allow elastic response and prevent damage from repeated seismic shocks. 8 PRECAST SOLUTIONS | JAN/FEB 2008

Table of Contents Feed for the Digital Edition of Precast Solutions - January/February 2008

Precast Solutions - January/February 2008 Contents Precast Concrete Short-Span Bridges Precast Micro-Reinforced Concrete A Winning Edge The Creative Edge TMI: Too Much Infiltration! Architectural Details Cast in Stone

Precast Solutions - January/February 2008

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