Mechanical and structural properties of polyvinyl alcohol fibre reinforced concrete (PVA-FRC)
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Concrete is a brittle material that has low tensile strength and low strain capacity. In fact, many deteriorations and failures in the concrete structures are due to the brittle nature of this material (Hamoush et al. 2010). These disadvantages may be avoided by adding short discontinuous fibres to plain concrete which has been a major motivation for many research works in recent years (Wu & Sun 2003). Fibres are added into a brittle-matrix composite to help improve three major aspects; toughness, ductility and strength (tensile) (Arisoy 2002). Fibres tend to increase toughness of the composite material by bridging the cracks and provide energy absorption mechanism related to de-bonding and fibre pull-out. Furthermore, they can increase the ductility of the composite by allowing multiple cracking. They may also help increase the strength by transferring load and stresses across the cracks. Advancement of fibre reinforced concretes (FRCs) started in the 1970s. By that time, only glass fibre and steel fibre were investigated (Perumalsamy & Surendra 1992). Synthetic fibres have become more attractive in recent years as reinforcements for cementitious materials. This is due to the fact that they can provide inexpensive reinforcement for concrete and if the fibres are further optimized, greater improvements can be gained without increasing the reinforcement costs (Li et al. 1991; Wang et al. 1989). Moreover, unlike the steel fibre which is highly corrosive in nature, there is no corrosion concern regarding synthetic fibres in concrete. During the past 20 years (since early 1990s), polyvinyl alcohol (PVA) fibre has been introduced in the production of cementitious composites (Li 1998; Redon et al. 2001; Shen et al. 2008; Sun & Wu 2008). PVA fibres act greatly in a cement based matrix with no coarse aggregates due to their surface formation and high strength (Li et al. 2001). The resulting composite, which exhibits a pseudo ductile behaviour, is called engineered cementitious composites (ECC). Although many research works have been performed to date on the properties of PVA fibre reinforced ECC, there has not been much investigation on the mechanical and structural characteristics of PVA fibre reinforced concrete. Accordingly, the objective of this study is to experimentally observe the effects of adding PVA fibres to the conventional concrete to assess its mechanical and structural properties. To achieve this aim, a comprehensive set of experiments were carried out to investigate the effect of PVA micro fibre addition on mechanical and structural properties of conventional concrete. Therefore, concrete mixes containing PVA fibres of varying lengths (6 and 12 mm) in different fibre volume fractions ranging from 0.125% - 1% were prepared and tested for their fresh and hardened properties. The optimum fibre contents in terms of FRC performance were then selected to cast several concrete beams. These beams have later been tested for 4-point monotonic and 3-point cyclic flexure, to assess their structural properties. Hammer test was also conducted to evaluate the dynamic characteristics of conventional and FRC specimens as well as concrete beams.
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