Nonconventional Concrete Technologies Renewal of the Highway Infrastructure (1997) / Chapter Skim
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3 Reinforcement
3 Reinforcement
Pages 53-62
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From page 53... ...
Conventional concrete technology utilizes composite theory to optimize the effects of various combinations of matrix materials, graded aggregates, and reinforcement materials (e.g., continuous rebar reinforcement and fiber) on overall performance and properties.
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From page 54... ...
These environmental conditions drive the specifications for concrete permeability, reinforcement cover, and possibly reinforcement coatings and alternative reinforcement materials, all of which are aimed at improving the clurability of concrete structures. Translating the property requirements of a concrete structural system into specific reinforcement requirements is a nontrivial exercise.
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From page 55... ...
Improved concrete durability may also require the use of discontinuous reinforcement to provide mechanisms for crack briciging, crack tip blunting, and crack cleflection. CONTINUOUS REINFORCEMENT The ancillary role that conventional cement plays in passivating the rebar poses some significant challenges in developing a nonconventional concrete.
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From page 56... ...
Alternative Continuous Reinforcement An alternative to protecting steel rebar would be the development of a replacement that does not degrade in chIoricle, neutral, or acid environments. Such a replacement might take the form of either a rigid composite structure, such as a fiber-reinforced plastic composite, or a linear or planar structure, such as a woven-fiber mat.
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From page 57... ...
Fiber-reinforced plastic composites are characterized by reasonable strength, low density, chemical resistance, and clurability, all of which can be tailored to meet performance needs. The resin matrix in a fiber-reinforcec} plastic composite provides structural continuity, transfers loacis among reinforcing fibers, ant!
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From page 58... ...
. In acldition, Japanese research indicates that fiber-reinforced plastic composites show excessive deformation uncler load due to low elastic moclulus and high creep (Henrichsen, 19961.
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From page 59... ...
~ _ . Deformation FIGURE 3-1 Tensile load versus deformation for conventional concrete and discontinuous-fiber-reinforced concrete showing the increased resistance to crack propagation and crack opening by the addition of discontinuous fibers.
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From page 60... ...
After the peak load produces matrix cracking, however, FRC can carry a significant level of Toad over a wide range of continued deflection (Figure - 29. The fibers hold the cracked concrete pieces together, provide a mechanism to blunt crack propagation, ant!
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From page 61... ...
. determination of the optimum volume fraction, mixing, and placement of discontinuous reinforcement as a function of concrete composition ant!
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From page 62... ...
shape memory alloys, which can exhibit high damping capacity and might improve earthquake resistance in large constructions (Van Humbeeck et al., 1996 . foams, porous materials, or three-climensional woven structures to absorb the energy and stress waves producecl by continuous pressure (the materials couIci also be infiltrates!
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