Test Methods for Durability of Polymeric Fibers in Concrete and UV Light Exposure

Abstract

Two test methods are presented that can be used for evaluating durability of polymeric fibers subjected to alkaline environment present in concrete and to ultraviolet (UV) light exposure. The test methods were used to evaluate three polymeric fibers: nylon, polypropylene, and polyester. Durability of the fibers in an alkaline environment was ascertained by measuring the flexural toughness of fiber reinforced concrete specimens that had been aged in lime saturated water maintained at 50 deg C. The UV light exposure test was conducted at a temperature of 65 deg C with intermittent water spray. The wet spray was used to simulate conditions in the field. Durability of the fibers was determined by measuring the retained tensile strength of the fibers after light exposure and by observing the surface characteristics of fibers under a microscope. The test results indicate that nylon and polypropylene fibers are durable in alkaline environment present in concrete. The nylon fibers, which were light stabilized, were determined to be stable under UV light exposure. Polypropylene fibers deteriorated under UV light, and the deterioration of the polypropylene single filament fibers was more rapid than for the fibrillated fibers. Hence these fibers should not be used in applications where the fiber contribution is needed at cracked-exposed sections.