Where to use - Glass fiber reinforced concrete (GFRC)

GFRC panels may have a thickness of as little as a half inch. With such a thin shell, there is no margin to take chances on a low quality concrete. That’s why leading GFRC producers around the world rely on Engelhard MetaMax® high reactivity metakaolin to boost the strength and durability of their products.
  
Over time, ordinary GFRC can lose some of its strength and ductility. Research has shown that this is due to the formation of lime crystals around the glass reinforcing fibers. Lime (also known as calcium hydroxide) is formed as a byproduct of the reaction between portland cement and water. When the lime crystallizes, it forms deposits that “pinch” the glass fibers so they cannot slip. Yet it is this slippage that gives GFRC its energy absorbing capability and toughness.

As a highly reactive pozzolan, MetaMax converts the lime in GFRC into calcium silicate hydrates (CSH) before the lime can damage the glass fibers. In fact, the CSH formed by MetaMax actually strengthens the concrete and makes it less porous. In testing at the NSF Center for Advanced Cement-Based Materials, Northwestern University, researchers found that, “The results indicate that the blended cement consisting of synthetic pozzolan metakaolin significantly improves the durability of GFRC composite.”*

The renovation of Shepard Hall at City College of New York provides a dramatic example of the benefit of MetaMax in GFRC. In an extensive program of accelerated aging tests conducted prior to selecting a cladding material for the project, GFRC with MetaMax outperformed ten other cladding products for resistance to weathering, discoloration, and environmental attack. And not only did MetaMax outperformed systems with silica fume and fly ash, its bright white color made it easier to match the color required for this historic structure. To date, more than 40,000 pieces of GFRC have been successfully installed on the project.

BASF is proud to be a partner with Saint-Gobain Vetrotex, producers of the Cem-FIL® glass fiber reinforcement for GFRC. According to them, “Metakaolin may also be added as partial cement replacement material to improve the long term properties of the GFRC.”  For information on Cem-FIL, click here.

Case studies: Shepard Hall, Alwyn Court

* “Marikunte, Aldea and Shah, “Durability of Glass Fiber Reinforced Cement Composites: Effect of Silica Fume and Metakaolin”, 1997, Elsevier Science Ltd.