Use of fibers for plastic shrinkage crack reduction in concrete

Use of discrete fibers to reduce plastic shrinkage cracking of concrete is discussed. The results presented cover a wide range of fibers in terms of their material properties such as modulus of elasticity, diameter, lengths, and surface characteristics. Fiber contents used ranges from 0.45 kg/m3 to 60 kg/m3 and the matrix composition evaluated vary from mortar to concrete with normal and low density aggregates. The influence of fiber properties, fiber geometries, volume fractions, and matrix compositions were evaluated for the crack reduction of concrete during the initial and final setting period. These cracks eventually influence the long-term durability of concrete. The results indicate that fibers provide a definite contribution to crack reduction and the major parameters that influence the crack reduction are: fiber count, geometry of the fiber, modulus of elasticity of the fiber, and fiber volume fraction. The fiber volume fraction needed for effective crack reduction ranges from 0.1 to 5 percent.