A tendon for prestressed concrete wherein inorganic particles are coated on an outer surface of a rod made of fiber reinforced plastic through a plastic adhesive layer. The inorganic particles are formed with minute rugged surface portions on the outer surface of the tendon for prestressed concrete, the rugged surface portions being firmly adhered to concrete. The inorganic particles are coated on the whole outer surface of the tendon for prestressed concrete, on the fixed portions at both ends, or on the fixed portions at both ends and on a portion subjected to the maximum bending moment.
A cell material structure for confinement of concrete and earth material, having a plurality of plastic strips bonded together on their faces in a side by side relationship at bonding areas which are staggered from strip to strip such that the plurality of strips may be stretched in a direction perpendicular to the faces of the strips to form a web of cells, the strips forming cell walls. At least one of the strips has an aperture through which a reinforcing member extends. Preferably, the reinforcing member is a tendon made of a polymer having a nominal breaking strength of from about 100 to about 2,500 lb.
A rod-shaped tension member formed of fiber reinforced composite material is utilized as an anchoring rod in foundation and mining construction, or as a reinforcing member in concrete and prestressed concrete construction. At least, in an axially extending region where it is to receive an anchoring member, such as a rod, the tension member has a continuous helical thread formed of alternating ribs and recesses. The anchoring member has a corresponding thread so that it can be screwed onto the tension member thread. An intermediate layer is provided between the threaded regions of the tension member and the anchoring nut, and is formed of a material affording large plastic deformation relative to the tension member when slight stress increases occur at overload conditions. Accordingly, between the threads on the tension member, and the nut, the plastically deformable intermediate layer has a strength less than that of the fiber reinforced composite material whereby it is subject to compression, acting transversely of the rod. As a result, stress peaks in the tension member are avoided by the plastic deformation of the intermediate layer.
Small cross-section composites are used as reinforcements for concrete. The composites include longitudinally oriented fibers embedded in a depolymerizable and repolymerizable thermoplastic matrix. The composites are mixed into the wet concrete and poured with the concrete to form a reinforced concrete structure.
Carbon fiber rovings for reinforcement of concrete are here disclosed which are obtained by sizing, with a sizing agent, strands each consisting of 100 to 1,000 monofilaments of mesophase pitch-based carbon fibers, and then bundling the thus sized 5 to 100 strands into one roving.
A method for producing flexible, low-bulk towpreg which involves powder coating a bundle of unspread fiber tows arranged in a predetermined cross-sectional shape, and the resulting towpreg. During the powder coating process, the resin powder particles do not enter into the fiber bundle, but rather only coat the surface fibers comprising the tows, resulting in dry fibers in the core of the towpreg and outer fibers which are coated with a discontinuous sheath of resin on the surface of the towpreg surrounding the core of dry fibers. The resin layer on the surface of the towpreg is formed by a partial melting of the powder particles. A post treatment process can be used to convert flat ribbon towpreg produced in accordance with the present invention into flexible unidirectional tape.
