Influence of sisal fibers on the mechanical performance of ultra-high performance concretes

This paper investigated the utilization of natural sisal fibers in ultra-high performance concrete (UHPC). UHPC mixtures containing sisal fibers with different lengths (6, 12, and 18 mm) and volume contents (1.0%, 2.0%, and 3.0%) were prepared. Flowability, mechanical strength, and interfacial bond behavior between fiber and matrix were tested for every mixture. The distribution of sisal fibers in the UHPC matrix was evaluated using the ultraviolet (UV) light and fluorescent whitening agent (FWA). Finally, the microstructures of typical samples were observed by a scanning electron microscope (SEM). Experimental results indicated that the flowability of the fresh UHPC mixture decreased with the increase of length and volume fraction of sisal fibers. The content of 2.0% sisal fibers with a length of 18 mm increased flexural strength and toughness of UHPC by 16.7% and 540.0%, respectively, compared with plain UHPC specimens. The pull-out load and pull-out energy increased with the length of sisal fibers. Moreover, the sisal fibers can be uniformly distributed in the UHPC matrix. Therefore, the utilization of sisal fibers to manufacture a low-cost and low energy-consumption UHPC has great potential.