Abstract
AbstractUltra-high-performance concrete (UHPC) incorporates a relatively large volume fraction of very dense cementitious binder with microscale fibers. The dense binder in UHPC can effectively interact with nano- and microscale reinforcement, which offers the promise to overcome the brittleness of UHPC. Nanoscale reinforcement can act synergistically with microscale fibers by providing reinforcing action of a finer scale, and also by improving the bond and pullout behavior of microscale fibers. Carbon nanofiber (CNF) and polyvinyl alcohol (PVA) fiber were used as nano- and microscale reinforcement, respectively, in UHPC. An optimization experimental program was conducted in order to identify the optimum dosages of CNF and PVA fiber for realizing balanced gains in flexural strength, energy absorption capacity, ductility, impact resistance, abrasion resistance, and compressive strength of UHPC without compromising the fresh mix workability. Experimental results indicated that significant and balanced gains...
Highlights
Experimental results and discussion The fresh mix flow test results for Ultra-high-performance concrete (UHPC) mixtures with carbon nanofiber (CNF) and/or polyvinyl alcohol (PVA) reinforcement systems are summarized in Figures 2 and 3 versus PVA fiber and CNF concentrations, respectively
It should be noted that the wide scatter in test results observed in Figure 3 is because the PVA fiber volume fraction is not constant for different data points depicted in this figure
Summary and conclusions A hybrid reinforcement system comprising CNF and PVA microfiber was optimized for balanced improvement of UHPC material properties
Summary
Ultra-high-performance concrete (UHPC) materials provide compressive strengths higher than 150 MPa (22 ksi) and tensile strengths greater than 8 MPa (1.1 Ksi) (Graybeal, 2007; Habel, Viviani, Denarié, & Brühwiler, 2006; Magureanu, Sosa, Negrutiu, & Heghes, 2012; Wille, Naaman, & Parra-Montesinos, 2011).The exceptional mechanical and durability characteristics offered by UHPC (FHWA, 2011; Van Tuan, Ye, van Breugel, & Copuroglu, 2011) are made possible by the use of high contents of cementitious binder with very low water/binder ratios (less than 0.25) (Barnett, Lataste, Parry, Millard, & Soutsos, 2010; Ding, Liu, Pacheco-Torgal, & Jalali, 2011; Peyvandi, Sbia, Soroushian, & Sobolev, 2013; Schröfl, Gruber, & Plank, 2012), dense packing (Wille, Naaman, El-Tawil, & Parra-Montesinos, 2012) particulate matter (aggregate, cement, supplementary cementitious materials, and inert powder) lowering maximum aggregate size, effective use of pozzolanic reactions to realize the binder structure and capillary pore system, and use of macro/microscale fibers (Kang & Kim, 2011; Yang, Joh, & Kim, 2011) to overcome the brittleness of UHPC.In order to overcome the extreme brittleness of UHPC, this cement-based material usually incorporates fibers (of different types). The work reported ; evaluate the synergistic action in mechanical properties of low-cost CNF and microscale poly vinyl alcohol (PVA) fiber in ultra-high-performance concrete. The maximum PVA fiber volume fraction beyond which fresh mix workability would be compromised was identified as 0.55% by volume UHPC materials.
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