Unique Polymeric Fiber and Fiber Delivery Systems for the Economic Preparation of High-fiber Content Concrete with Superior Physical Properties

Book excerpt: This report documents the results from an investigation of a new polymer fiber and unique delivery system for charging fibers into concrete mixtures. The straight Polyolefin fibers are available in two sizes: (1) 0.63 mm in diameter and 50 mm long, and (2) 0.38 mm in diameter and 25 mm long. Each of the two sizes of fibers is packaged in bundles approximately 50 mm in diameter. Each. bundle is encased with paper tape bound with a water-soluble glue. The fibers are charged into the concrete mixture in mass. Approximately 3 to 10 min of mixing time is necessary to uniformly distribute the fibers throughout the concrete mixture, depending upon the fiber content, consistency of the concrete mixture, and the type of mixer being used. Fresh and hardened properties were evaluated in mixtures containing up to 15 kg/cu m. The results indicate that concrete mixtures with the Polyolefin fibers can be produced having adequate workability and finishability if proportioned properly. Addition of the Polyolefin fibers does not significantly influence the compressive nor first-crack flexural strength, freezing-and-thawing resistance, drying shrinkage, nor the chloride permeability of concrete mixtures. However, the presence of the Polyolefin fibers does influence the post-crack behavior of concrete mixtures. Impact resistance and flexural toughness are improved as the fiber loading increases. A 6,100-m whitetopping demonstration project was constructed on a heavily traveled interstate in Mississippi. The whitetopping was 100 mm thick. Details of the specifications, construction, and early-time performance are given.