Literature Review and Industry Survey of Recycled Fibers from Novel and Existing Source Materials for Concrete Use

Research has demonstrated the multiple benefits of fibers for the early and late-age performance of concrete pavements and bridge decks. Many research studies have also shown that the expected enhancements in properties of concrete with recycled fibers could be commensurate with those of concrete reinforced with virgin fibers. However, compared with virgin polymeric fibers and steel fibers from primary steel, recycled fibers and fibers from natural sources are not as commonly implemented in construction due to several barriers. Some of these obstacles include a lack of research on recycled fibers, leading to gaps in technical performance data, case studies, test tracks, and pilot projects. The primary reason for the lack of research is related to gaps in information regarding the quality of recycled fibers compared to virgin fibers. To help overcome some of these barriers, this study included a comprehensive survey of concrete fiber suppliers. Those suppliers with recycled fiber and natural fiber manufacturing lines were identified and interviewed. The categories of fibers included in this report are recycled polymeric fibers, natural fibers mainly from cellulose, recycled steel fibers, carbon and glass fiber-reinforced polymer composites (for example, from end-of-life windmill blades), recycled carbon fibers, and glass and basalt fibers. The information gathered from the manufacturers is summarized in this report and includes the feedstock material, recycling process, geometric properties of fibers, recommended load for concrete flatwork applications, performance data (if available), cost, and environmental product declaration, if available. In addition to manufacturers’ surveys, a synthesis of performance in concrete is provided based on published technical literature for each fiber type. The topics included in the literature review are fiber dispersion and the impacts of fibers on the workability of concrete, plastic and drying shrinkage, strength and post-cracking performance, and durability of concrete. Based on this comprehensive review, many fibers from recycled and natural sources were identified for each source material. These fibers are already available on a large scale in the market, and several have been successfully implemented in concrete applications. In the case of steel and carbon fibers, recycled fibers are available at a fraction of the cost of virgin fibers, making this product more feasible in construction. Cellulosic fibers appear to have great potential to reduce plastic shrinkage cracking in concrete. Glass and basalt fibers are from natural silica sources and offer many structural advantages to the performance of concrete. These fibers are recommended for laboratory testing in the next phase of the project.