Concrete reinforced with irradiated nylon fibers
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mina Menchaca-Campos Centro de Investigación en Ingeniería y Ciencias Aplicadas (CIICAp), Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62210, Mexico; and Center for the Study of Matter at Extreme Conditions (CeSMEC), Florida International University, Miami, Florida 33199
Susana Hernández-López and Enrique Vigueras-Santiago Laboratorio de Investigación y Desarrollo de Materiales Avanzados (LIDMA), Facultad de Química, Universidad Autónoma del Estado de México, Km.12 de la carretera Toluca-Atlacomulco, San Cayetano 50200, Mexico
Witold Brostow Laboratory of Advanced Polymers & Optimized Materials (LAPOM), Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76203-5310 (Received 25 May 2005; accepted 3 November 2005)
Polymeric fibers have been used since the 1980s for improvement of the concrete. However, high mechanical performance has been obtained at high cost and using complex technologies. At least two parameters are important here: dimensions and surface characteristics of the fibers. We have modified nylon 6,12 fiber surfaces by 5, 10, 50, and 100 kGy gamma irradiation dosages. Tensile strength of the irradiated fibers was determined and then the fibers mixed at 1.5%, 2.0%, and 2.5% in volume with Portland cement, gravel, sand, and water. The compressive strength of the fiber reinforced concrete (FRC) was evaluated and the results were compared with results for similar materials reported before. The highest values of the compressive strength of FRC are seen for fibers at 50 kGy and 2.0% in volume of fiber; the strength is 122.2 MPa, as compared to 35 MPa for simple concrete without fibers. We advance a mechanism by which the fiber structure can be affected by gamma irradiation resulting in the compressive strength improvement of the concrete.
I. INTRODUCTION
Micro- or macro-synthetic nylon fibers have been in use since the early 1980s for secondary temperatureshrinkage reinforcement in shotcrete and concrete. In the micro case, monofilaments and fibrillated shapes are used; the monofilaments are available in various lengths from 13 to 38 mm, with the 20-mm size used most often. Since these fibers are very thin, their number per weight (fiber count) is in the range of millions per 1 kg of concrete, for example, 77 million/kg when using fibers with 19 mm length.1 Several improvements can occur when microsynthetic nylon fibers are added to the concrete, typically at dosage rates of 0.6 to 0.9 kg/m3 of mixture. a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0058 484
http://journals.cambridge.org
J. Mater. Res., Vol. 21, No. 2, Feb 2006 Downloaded: 26 Jan 2015
The first potential improvement is reduction in craze cracking due to compressive stress, plastic shrinkage cracking, and plastic settlement. The reduction in cracking and settlement prior to setting produces concrete with improved long-term durability. The second improvement relates to increasing high impact resistance by lowering the extent of stretch
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