Influences of Fibers on Drying Shrinkage of Fiber-Reinforced Cementitious Composite

An analytical model has been formulated for the drying shrinkage performance of a fiber-reinforced cementitious composite. The model is based on the assumption that shear stress is produced between the fiber and surrounding matrix as the matrix shrinks. This shear stress in turn influences the matrix deformation behavior resulting in macroscopic composite shrinkage lower than that of a pure cement-based matrix. Through systematic derivation, a free shrinkage expression, which reflects the influences of the matrix and fiber properties as well as fiber orientation characteristics, is presented. A parametric study, including the influence of elastic moduli of the fiber and matrix, fiber dimension, and fiber content in the case of 3D fiber distribution, is carried out. The model results indicate that shrinkage of a fiber-reinforced cement-based composite is significantly influenced by elastic moduli of fiber and matrix as well as fiber length and thickness (i.e., diameter for fiber with a circular cross section). Model predictions based on independent parametric inputs compare favorably with experimental measurements of free shrinkage of fiberreinforced mortar and concrete.