International Journal of Material and Mechanical Engineering (IJMME), Volume 5 2016 www.ijm‐me.org doi: 10.14355/ijmme.2016.05.002
Effects of Concrete Compressive Strength of Steel and Polyester Fiber Admixtures and Vacuumed Dewatering Application Hakan Bolat1, Mustafa Çullu2 Gumushane University Natural Science and Engineering Faculty, Department of Civil Engineering 29100 Gumushane, Turkey, 1‐2
1hbolat@gmail.com; 2mustafacullu@hotmail.com Abstract Vacuum dewatering method is the process of removing some of mixing water from fresh concrete. Therefore, excess mix water damages are prevented and mechanical strengths increase after concrete takes the shape of the mold. Fiber admixtures are mostly used for increasing the flexural strength of concrete. However, there are also effects on the compressive strength. In this study, the effects of application of the vacuum dewatering on the compressive strength of concrete are examined with addition of steel and polyester fibers. The parameters of the study are fiber types (steel, polyester), fiber ratios (3 different ratios), fiber lengths (long, short) for concrete class (C16/20‐C25/30‐C35/45 according to EN) and two different application methods (normal, vacuum). The compressive strengths of the concrete prepared in accordance with these parameters are determined after 1, 3, 7 and 28 days. Thus, it is investigated that each of the parameters is affected concrete compressive strength. Keywords Concrete; Compressive Strength; Steel; Polyester Fibers
Introduction Fibers are generally used to increase flexural strength of concrete [1‐3]. However, physical and mechanicalcharacteristics of concrete are affected by type, length, geometric shape and ratio of the fiber [4‐5]. The most important mechanical characteristic of concrete is compressive strength [1‐3]. Itʹs been reported in the literature that fiber admixtures do not have a great influence on compressive strength of concrete, however, any change in fiber parameters also affects compressive strength of concrete [6,7]. If steel fibers with appropriate characteristics are added, they will make a significant contribution to the mechanical strength of concrete [4,6,8]. However if concrete is exposed to conditions such as adverse weather conditions, chemicals, freeze‐thaw, becoming wet or dry, steel fibers in concrete lose their characteristics depending on time [6,9,10] (Fig 1). Synthetic fibers are concrete admixtures developed as an laternative to steel fibers [9‐11]. Although breaking strength of synthetic fibers is not as high as that of steel fibers, their strength against other negative conditions is much higher and they show much more positive behaviors compared to steel fibers over time [8‐10]. One of the factors affecting mechanic behaviors of concrete is the mixing water. Parameters of the mixing water affecting concrete can be summarized as follows [1‐3,7]: • Using water the amount of which is either more or less than what is necessary • Using either too cold or hot water • Using water with unwanted physical and chemical properties • Using too much or too little water Reasons for such parameters occuring can be summarized as follows;
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