Christian
Meyer and Gregor Vilkner
Columbia University, New York
Thin-sheet concrete products have attracted the attention of researchers and concrete producers alike in recent years because of their numerous potential applications. In conventional steel reinforced concrete elements, the cover needed to protect the steel against corrosion calls for a minimum sheet thickness of at least 5 to 7 cm. The tendency of the ribs of standard reinforcing bars to spall off thin concrete covers may require a further increase of the minimum plate thickness. For non-metallic reinforcement no corrosion protection is needed, and thicknesses of a few mm are theoretically possible. Woven fabrics or fiber mesh, also referred to as textile reinforcement, have proven to be a viable form of such reinforcement. The rovings are curved at points of intersection, caused by the weaving process. It has been observed by other researchers that woven fabrics, when stressed as ordinary reinforcement, need to be straightened before they contribute in the load carrying process (Curbach 1999). This delay inhibits distributed cracking to some extent, but if the fabrics are stretched slightly before being built in, such curvature effects become negligible. Prestressing the embedded reinforcement, whether provided in the form of single rovings or continuous fiber mesh, further improves the mechanical properties of structural members and enhances their durability because of the absence of cracks (Krüger 2004, Vilkner 2003).
The substitution of crushed glass for natural aggregate opens up additional options, primarily in the field of architectural concrete, because of the esthetic potential of colored glass. An important prerequisite is an effective measure to counter the potentially damaging effects of alkali-silica reaction (ASR). At Columbia University, a project is currently under way to explore the possibilities of prestressing thin sheet glass concrete products. There are numerous performance criteria that need to be satisfied by the fiber mesh material in order to qualify for the tasks on hand. Most promising to date are high-performance materials such as aramid and carbon fiber mesh. This paper describes work in progress, pointing out some of the issues of mechanical behavior involved and technical problems that need to be overcome, before such thin sheets can be mass-produced commercially.
References
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Columbia University, New York
Thin-sheet concrete products have attracted the attention of researchers and concrete producers alike in recent years because of their numerous potential applications. In conventional steel reinforced concrete elements, the cover needed to protect the steel against corrosion calls for a minimum sheet thickness of at least 5 to 7 cm. The tendency of the ribs of standard reinforcing bars to spall off thin concrete covers may require a further increase of the minimum plate thickness. For non-metallic reinforcement no corrosion protection is needed, and thicknesses of a few mm are theoretically possible. Woven fabrics or fiber mesh, also referred to as textile reinforcement, have proven to be a viable form of such reinforcement. The rovings are curved at points of intersection, caused by the weaving process. It has been observed by other researchers that woven fabrics, when stressed as ordinary reinforcement, need to be straightened before they contribute in the load carrying process (Curbach 1999). This delay inhibits distributed cracking to some extent, but if the fabrics are stretched slightly before being built in, such curvature effects become negligible. Prestressing the embedded reinforcement, whether provided in the form of single rovings or continuous fiber mesh, further improves the mechanical properties of structural members and enhances their durability because of the absence of cracks (Krüger 2004, Vilkner 2003).
The substitution of crushed glass for natural aggregate opens up additional options, primarily in the field of architectural concrete, because of the esthetic potential of colored glass. An important prerequisite is an effective measure to counter the potentially damaging effects of alkali-silica reaction (ASR). At Columbia University, a project is currently under way to explore the possibilities of prestressing thin sheet glass concrete products. There are numerous performance criteria that need to be satisfied by the fiber mesh material in order to qualify for the tasks on hand. Most promising to date are high-performance materials such as aramid and carbon fiber mesh. This paper describes work in progress, pointing out some of the issues of mechanical behavior involved and technical problems that need to be overcome, before such thin sheets can be mass-produced commercially.
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