Cast-in-place cellulose fiber-reinforced cement paste, mortar, and concrete

Fiber-reinforced concrete is a fast-growing technology. This research considers the use of cellulose fibers as an inexpensive alternative to synthetic fibers. This study characterizes the behavior of cellulose fiber-reinforced paste, mortar, and concrete and investigates rheological, dispersion, and mechanical properties of the materials. The addition of cellulose fibers to a cementitious material stiffens the matrix. This stiffening limits the maximum usable fiber volume. At fiber volumes used, fibers offer little improvement in flexural properties. Optical and scanning electron microscopy are used to inspect fiber dispersion. A technique is developed to locate fibers in hardened specimens. Correlations among fiber dispersion, mechanical performance, and rheology are investigated. Restrained ring shrinkage tests are performed on paste and mortar. Fibers are found to reduce the width of shrinkage cracks in both materials. Fiber dispersion, matrix rheology, and mechanical performance cannot be correlated. Fibers disperse well under normal mixing conditions, regardless of matrix rheological properties.