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دانلود ترجمه مقاله استحکام خمشی و بهره وری فیبر بتن اصلاح شده با پلیمر و متراکم شده با غلتک – مجله الزویر
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(1) در مقایسه با بتن مسلح شده با فیبر فولاد معمولی، بتن اصلاح شده با پلیمر، متراکم شده با غلتک یا غلتکی و مسلح شده با فیبر فولاد، مقاومت خمشی بسیار بالایی به معرض نمایش گذاشت. این ماده برای نوسازی و ترمیم سنگفرش بتنی فرسوده بسیار مطلوب می باشد.
. Introduction Part of the ‘Green Overlays’ research lead by the authors for the last four years involved the development of special concrete mixes used as overlay material, fully bonded on worn concrete pavements. This material exhibits high flexural, shear and bond strengths and high resistance to reflection cracking. It also demonstrates unique placeability and compactability properties, hence it can be placed on the damaged surface by an asphalt paver and compacted by a vibrating roller [1]. The mixes were named steel-fibre-reinforced, roller-compacted, polymer modified concrete (SFR–RC–PMC). The steel fibre in the mix retards and contains reflective cracking, the polymers enhance its strength and achieve good bond with the old concrete and the roller compaction ensures quick construction. These types of mixes were different from conventional roller-compacted concrete (RCC). Specifically, the optimal water content of the former determined by the modified-light (M-L) compaction method proposed by the authors [1] was usually around 17 kg higher than the latter, designed by the modified Vebe method [2,3] for 1 m3 of concrete, for the same mix proportion [1]. Flexural strengths of conventional steel fibre reinforced concrete (SFRC) have been investigated since the 1980s [4–11]. A vast amount of literature deals with flexural strength, residual flexural strength, toughness, toughness indexes, crack development and propagation, fibre bridging law, fracture energy, and so on. Neocleous et al. [12,13] investigated the flexural performance of steel fibre-reinforced RCC for pavements, while the steel fibres were recovered from used tyres, whereas the mix was conventional RCC. Kagaya et al. [14] investigated the mix design method for steel fibre reinforced RCC pavements by employing the modi- fied Proctor compaction method. It is seen that the mechanical properties of SFR–RC–PMCs have not been investigated to date. In addition, steel fibres in these types of mixes may exhibit a different behaviour to those in conventional SFRCs, due to the fact that the former contains much less cement paste than the conventional concrete, and roller compaction may result in deformation of steel fibres. Furthermore, the flexural performance of PVA (Polyvinyl Alcohol) modified concrete has rarely been investigated. Therefore, it is crucial to investigate the flexural performance of SFR–RC–PMC for overlay pavement design. This article aims to reveal the flexural performance, especially the equivalent flexural strengths of SFR–RC–PMC for overlay pavement design and the efficiency of fibres in RCC. 2. Mix proportion and specimen preparation The ingredient materials used (apart from the 50 mm-long fibre) were presented in Ref. [1] in detail. The 50 mm-long fibre was the hooked-end type, with an aspect ratio of 80. The test beams of eight mixes are tabulated in Table 1. Two types of polymers, i.e. SBR (Styrene Butadiene Rubber) and PVA (Polyvinyl Alcohol) and two types of steel fibre, i.e. 35 mm-long and 50 mm-long were used. Super-plasticizer was added in the PVA modified concrete to reduce water content and obtain high strength, while the SBR modified concrete did not incorporate any admixtures. Among a total of eight mixes, five mixes, SBRPMC1%-35, SBRPMC1.5%-35, SBRPMC2%-35, PVAPMC1.5% and SBRPMC1.5%-50 (final numbers of mix ID indicate length of fibres), were SFR–RC–PMC, whose water contents were determined using the M-L compaction method [1]. Mix SBRPMC0%, did not contain fibre and was used as the matrix of mixes SBRPMC1.5%-35 and SBRPMC1.5%-50. Also, it was purposely used for the evaluation of the relative toughness of the same mixes. All beams of the six mixes were fabricated in steel moulds using the vibrating compactor shown in Fig. 1, which was purposely designed for specimen formation. The dimensions of the beams of the six mixes were 80 (W) 100 (H) 500 (L) mm. The mixing procedure can be found in Ref. [1]. The mix compaction was carried out in two layers. Each layer was about 40–50 mm thick. The vibrating compaction lasted 30–50 s per layer for SBRPMC, and 60–90 s for PVAPMC until mortar formed a ring around the perimeter of the moulds. The surface of each layer was roughened before accepting the next layer of material. The specimens were de-moulded in twenty-four hours. The SBR modified concrete specimens were cured in water for five days whereas the PVA specimens for seven days, followed by air curing until the test day. The ages of the specimens for tests were 28–40 days. The conventional SFRC, i.e. Con.SBRPMC1.5%-35, was intended for comparison with the mix SBRPMC1.5%-35 to reveal the efficiency of fibres. The former had the same ingredients and mix proportion as the latter except for the water content. The mix Con.SBRPMC0% acted as the matrix of mix Con.SBRPMC1.5%-35. The slump of the mix Con.SBRPMC1.5%-35 was 130 mm. The dimensions of the beams of both mixes were 100 (W) 100 (H) 500 (L) mm, fabricated in steel moulds on the vibrating table. The mixing and curing procedures of both mixes were the same as for mix SBRPMC1.5%-35. |
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