Fibras em geral

CONCRETE REINFORCEMENT

WITH

RECYCLED FIBERS

By Youjiang Wang,1 H. C. Wu,2 and Victor C. Li3
ABSTRACT: Fiber reinforcement can effectively improve the toughness, shrinkage, and durability characteristics of concrete. The use of recycled fibers from industrial or postconsumer waste offers additional advantages of waste reduction and resources conservation. This paper reviews some of the work on concrete reinforcement using recycled fibers, including tire cords/wires, carpet fibers, feather fibers, steel shavings, wood fibers from paper waste, and high density polyethylene. This paper also provides a summary of the properties and applications of concrete reinforced with these fibers.

INTRODUCTION Concrete is the most frequently used construction material in the world. However, it has low tensile strength, low ductility, and low energy absorption. An intrinsic cause of the poor tensile behavior of concrete is its low toughness and the presence of defects. Therefore improving concrete toughness and reducing the size and amount of defects in concrete would lead to better concrete performance. An effective way to improve the toughness of concrete is by adding a small fraction (usually 0.5–2% by volume) of short fibers to the concrete mix during mixing. In the fracture process of fiber reinforced concrete (FRC), fibers bridging the cracks in the matrix can provide resistance to crack propagation and crack opening before being pulled out or stressed to rupture. After extensive studies it is widely reported that such fiber reinforcement can significantly improve the tensile properties of concrete. Orders of magnitude increases in toughness (energy absorption) over plain concrete is commonly observed (ACI 1982; Keer 1984; Wang et al. 1987; Bentur and Mindess 1990). Another application of fiber reinforcement is for the reduction of the shrinkage and shrinkage cracking of concrete associated with hardening and curing. Plastic shrinkage cracks occur in fresh, unhardened