Precast Solutions - January/February 2008 - (Page 9)

and the concrete will have the texture of cloth. The aesthetic options also include form liners, integral colorants and other precasting techniques. Very thin veneers of glass and stone can be laminated to thin MRC panels to combine the aesthetics of the veneer with the strength of MRC. If a blast or impact occurs, the veneer will adhere to the concrete to reduce the risk of dangerous fragments or shards. This precast MRC portal is 14 feet high and has a wall thickness ranging from 3 to 4 inches – far thinner than would be possible using conventional materials. SUSTAINABLE AND PRACTICAL MRC is well-suited for sustainable construction. Both the mortar and steel mesh contain recycled-content materials. As with most precast concrete, MRC can be produced locally using locally extracted raw materials. And when made with white cementitious materials, MRC can reduce the heat island in urban environments by reflecting sunlight, an intriguing option given the possibility of using MRC as an exposed roof deck. Far more environmentally significant are the breakthroughs enabled by MRC’s higher strength-toweight ratio. MRC reduces the quantity of material required to achieve a given structural performance and this, in turn, reduces the material required to support an element’s dead load. The structure is thus lighter and uses less material with the added benefit of reducing energy consumption, pollution and other transportationrelated impacts. The material’s strength and durability also contributes to a long service life for a structure. Lehigh University, Southwest Research Institute and other leading research organizations have tested MRC to North American standards. The International Code ARCHITECTURAL POSSIBILITIES Conference-Evaluation Service (ICC-ES) is currently reviewing acceptance criteria for the material. Engineers, precasters and contractors are being recruited and trained to work with this material. And new applications for MRC are being identified every week. As the development of new industry standards continues, MRC can be specified using performance specifications, much like precast is currently specified – showing the design loads in the contract documents and allowing the precast supplier to engineer a system that optimizes the performance of the concrete. For additional information, visit www.excendinc.com. Michael Chusid is an architect, a Fellow of the Construction Specifications Institute and a member the American Concrete Institute. His firm, Chusid Associates, investigates and reports on innovative building materials. He can be reached at www.chusid.com. Thinner, lighter and stronger precast elements will lead to exciting innovations in design. Peter DiMaggio, P.E., principal of structural engineering firm Weidlinger Associates, has studied MRC and says, “With MRC, I get to rethink everything I design in concrete.” A precast entry portal (see photo above) demonstrates how MRC has already been employed to produce complex structures far beyond the limits of previous concrete technology. Another example is a prestressed concrete plank that exhibits slenderness not practical with conventional concrete. Nearly any surface texture can be replicated using MRC, because the slurry takes on the finish of the mold in which it was cast. Cast it against smooth plastic, and the concrete will shine like plastic. Or cast it onto fabric, JAN/FEB 2008 | PRECAST SOLUTIONS 9 http://www.excendinc.com http://www.chusid.com

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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