Abstract
Fiber-reinforced cementitious composites (FRCC) are a class of materials made by adding randomly distributed fibers to a cementitious matrix, providing better material toughness through the crack bridging behavior of the fibers. One of the primary concerns with FRCCs is the behavior of the fiber when a crack is formed. The fibers provide a stress-bridging mechanism, which is largely determined by the bond that exists between the concrete and the fiber’s outer surface. While many studies have determined the properties of FRCCs and potential benefits of using specific fiber types, the effects of low temperature or cold plasma treatment of polymer fibers on the mechanical behavior of the composite material are limited. Polymer fibers are notable for their low density, ductility, ease of manufacture, and cost-effectiveness. Despite these advantages, the surface properties of polymers do not enable the bonding potential given by steel or glass fibers when used in untreated FRCC, resulting in pull-out failures before the full displacement capacity of the fiber is utilized. For this reason, modification of the surface characteristics of polymer fibers can aid in higher bonding potential. Plasma treatment is a process wherein surfaces are modified through the kinetics of electrically charged and reactive species in a gaseous discharge environment. This paper is a preliminary study on the use of atmospheric pressure plasma generated at approximately room temperature. This atmospheric, cold plasma treatment is a method for improving the mechanical properties of FRCC using polymeric fibers. In this study, polypropylene and polyvinyl-alcohol fibers were cold plasma treated for 0, 30, 60, and 120 s before being used in cementitious mortar mixtures. Compression and flexure tests were performed using a displacement-based loading protocol to examine the impact of plasma treatment time on the corresponding mechanical performance of the fiber-reinforced cementitious composite. The experimental results obtained from this study indicate that there is a positive correlation between fiber treatment time and post-peak load-carrying capacity, especially for specimens subjected to flexural loading.
Highlights
Additions of fibers to concrete systems have long been known to improve concrete durability, increase ductility, and improve overall cracking resistance of concrete [1,2,3]
The observed response of the specimens in this study suggests that cold plasma treatment positively alters the bonding potential and interaction between the fiber surface and the mortar as a function of treatment time
Compressive PP specimens and polyvinyl alcohol (PV) specimens did not exhibit a strong relationship between treatment time and post-peak capacity; it was observed that the longest treatment time was associated with a higher residual load capacity during strain softening
Summary
Additions of fibers to concrete systems have long been known to improve concrete durability, increase ductility, and improve overall cracking resistance of concrete [1,2,3]. While steel fibers tend to offer the best performance in terms of mechanical properties improvement, polymeric fibers can increase performance at a significantly lower cost [4]. Finding ways to improve the performance of concrete made with polymeric fibers, without significantly increasing cost, may provide significant economic benefits as well as performance improvements. Due to the low tensile strength characteristics of conventional concrete, the inclusion of fibers with a high tensile strength enhances the ductility and cracking characteristics of the composite. These enhancements are achieved by restraining crack openings when mechanical loading or environment cause stresses that exceed the cracking stress of the cementitious materials. The use of synthetic fibers manufactured from naturally occurring macromolecules and synthetic polymers as reinforcement for cementitious materials has been adopted as an alternative to steel and glass fibers due to their effectiveness and relatively low cost [8]
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