دانلود رایگان مقاله لاتین الیاف بازالت از سایت الزویر
عنوان فارسی مقاله:
تاثیر الیاف بازالت جمع شدگی پلاستیکی آزاد و محدود
عنوان انگلیسی مقاله:
Influence of basalt fibres on free and restrained plastic shrinkage
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Chopped basalt fibre is a relatively new concrete reinforcing material, with excellent mechanical properties and an environmentally friendly manufacturing process. The majority of research into basalt fibre reinforced concrete has focused on its mechanical properties [1e3]. In these studies, the results do not suggest the fibres are particularly effective in enhancing the post-cracking response of the concrete, which is one of the most significant benefits of fibre reinforcement [4]. Previous research has also indicated basalt fibres without any protective coating suffer from a lack of long-term durability in the alkaline environment of concrete [5,6]. Until this problem is resolved, a useful application of the fibre in its current state of development could be in enhancing the durability of concrete by preventing early-age cracking due to plastic shrinkage. It seems probable the fibres could be effective in this regard before any potential degradation negates their benefit. Plastic shrinkage refers to the volumetric contraction of cementbased materials that occurs during the first few hours after placement, while the material is in a plastic state. The contraction is driven by a combination of autogenous mechanisms and capillary pressure that develops in the pore structure near the surface when the rate of water evaporating from the concrete exceeds the rate at which it can be replaced by rising bleed water. When restrained, shrinkage will induce tensile stresses. If those stresses exceed the tensile strength of the concrete, it will crack. Restraint is generally present to at least some degree in practical applications by internal factors, such as rebar and aggregate, or by external factors, such as connections to walls and columns. Although initially shallow, plastic shrinkage cracks can grow to full-depth over time [7]. The cracks are not only unsightly, but they allow the penetration of deleterious substances and can lead to the rapid deterioration of structures; most notably the penetration of water and chlorides enabling the corrosion of embedded steel reinforcement. Shrinkage cracking is generally most prominent in structures with a large surface area to volume ratio, including: slabs-on-grade, tunnel linings, and repair overlays. One prominent example is the reduced serviceability of bridge decks due to early-age cracking. A number of reports published from various state departments of transportation (DOTs) in the United States of America suggest that shrinkage is a major contributing factor to early-age cracking [8e11]. In these reports, shrinkage refers to the strain that develops at both an early-age (plastic shrinkage), and over a longer duration after the concrete has hardened (drying shrinkage). However, according to the Transportation Research Board [12], the mechanisms that lead to plastic shrinkage cracks do not explain full depth cracks, and therefore, it is probable drying shrinkage can propagate plastic shrinkage cracks. Since cracks in concrete can propagate at a stress lower than that required to initiate them [13], the control of plastic shrinkage cracking should be a key design consideration in regards to mitigating cracking at later ages, and in-turn, minimizing long-term maintenance costs. It has been well established that the addition of short, randomly distributed fibres to concrete is an effective method in mitigating plastic shrinkage cracking. The fibres are effective in this regard for two reasons: first, they reduce the overall shrinkage strains and lower the possibility of tensile stresses exceeding tensile strength, and second, the fibres are able to restrict their development if they do occur [14]. According to Naaman et al. [15], the addition of any fibre with a diameter smaller than 40 mm, an aspect ratio above 200, in volume fractions of 0.2%e0.4%, should effectively eliminate plastic shrinkage cracking in concrete. Hence, it is unsurprising such a wide variety of fibres have been shown to be beneficial in this regard, including: steel, glass, various synthetic fibres (polypropylene, polyethylene, polyvinyl, and carbon), and various natural fibres (sisal, coconut, flax, and cellulose) [15e20]. However, the mechanisms by which different fibres reduce plastic shrinkage strain, and the resultant cracking, is not as thoroughly studied. This is an important consideration in order to understand the circumstances in which the use of a particular type of fibre is most effective.
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کلمات کلیدی:
Effect of Chopped Basalt Fibers on the Mechanical Properties and ... https://www.hindawi.com/journals/amse/2014/587686/ by T Ayub - 2014 - Cited by 5 - Related articles Jul 2, 2014 - Abstract. This paper presents the mechanical properties and the microstructure of the high performance fiber reinforced concrete (HPFRC) ... [PDF]Properties and applications of basalt fibre reinforced concrete scholar.uwindsor.ca/cgi/viewcontent.cgi?article=6627&context=etd by JS Branston - 2015 Dec 14, 2015 - basalt fibre reinforced concrete. Submitted, Construction and Building Materials. Chapter 3. Influence of basalt fibre on free and restrained ... The Influence of Steel and Basalt Fibers on the Shear and Flexural ... basalt.today › Reseach Mar 1, 2017 - The tests results confirmed: steel and basalt fibers in reinforced concrete ... Three series of single span free supported model beams were ... [PDF]Effect of Basalt Fibre on Mechanical Properties of Concrete Containing ... https://www.rroij.com/.../effect-of-basalt-fibre-on-mechanical-propertiesof-concrete-c... Jul 18, 2014 - KEYWORDS: Fibre reinforced concrete; basalt fibre; mechanical .... has uniform colour i.e. grey with a light greenish shade and is free from ... Materials | Free Full-Text | Effect of Hybrid Talc-Basalt Fillers in the ... www.mdpi.com/1996-1944/8/12/5473/htm by R Huang - 2015 - Related articles Dec 8, 2015 - Hybrid basalt fiber (BF) and Talc filled high density polyethylene ... The composite flexural and impact strength properties increased, and the ... [PDF]a review of the effect of basalt fibre lengths and proportions on ... - IJRET esatjournals.net/ijret/2015v04/i01/IJRET20150401069.pdf by S Elshafie - Cited by 4 - Related articles because different lengths and proportions of basalt fibres have an effect on the mechanical ... properties of concrete improved significantly when using basalt fibres with a length between ..... Projects, Western Kentucky University, Free acess. Mechanical Performance of Reinforced Concrete with Different ... https://www.omicsgroup.org/.../mechanical-performance-of-reinforced-concert-with-... This paper discusses the effect of the fraction (0.2-0.3% by volume) and length (22 mm and 24 mm) of basalt fibre on the mechanical properties of concrete.
