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Abstract

Macro recycled plastic fibre offers significant environmental benefits over virgin plastic fibre and steel reinforcement. However, as there is limited research on performance of recycled plastic fibre in concrete, it has not yet been widely adopted by the construction industries. In this research, post-cracking performance of different kinds of recycled polypropylene fibres from industrial waste was studied and compared with that of virgin polypropylene fibre in concrete. The diamond-indent recycled fibres showed a good balance of tensile strength, Young's modulus and concrete bonding, thus producing brilliant post-cracking performance. This research proved the feasibility of using recycled fibres as reinforcement in concrete footpaths.

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... Fraternali et al. [18] Italy PET Alkali resistance and flexural response Koo et al. [19] Korea PET Addition of Hwangtoh (clay) Fraternali et al. [20] Italy PET Straight and crimped fibres. Seawater curing Yin et al. [21] Australia HDPE/PP Fibre properties and mechanical properties Yin et al. [22] Australia PP/HDPE Fibre preparation and properties Spadea et al. [23] Italy Nylon Fibre from fishing nets Ghernouti et al. [24] Algeria Various Mechanical properties Yin et al. [25] Australia PP Life Cycle Assessment of fibre reinforced footpaths Borg et al. [26] Malta PET Early-age performance Particles/aggregates Batayneh et al. [27] Jordan s/d Glass, plastic and recycled concrete Marzouk et al. [28] France PET Mechanical properties Ismail and Hashmi [29] Iraq LDPE/PS Mechanical properties Panyakapo and Panyakapo [30] Thailand Melamine Mechanical properties Dweik et al. [31] Palestine Melamine Mechanical and thermal properties Yesilata et al. [10] Turkey PET Thermal insulation of different plastics aggregates Choi et al. [32] Korea, Canada PET Waste PET bottles coated with powder from river sand Albano et al. [33] Venezuela PET Mechanical properties for different particle sizes Kou et al. [34] Hong Kong PVC Mechanical properties Akçaözoglu et al. [35] Turkey PET Mechanical properties Frigione [36] Italia PET Mechanical properties Hannawi et a. [37] France PET/PC Mechanical properties Casanova-del-angel and Vázquez-Ruiz [38] Mexico PET Mechanical properties Ferreira et al. [39] Portugal PET Different curing conditions Akçaözoglu et al. [40] Turkey PET Mechanical properties Ávila Córdoba et al. [41] Mexico PET Mechanical properties Saikia and De Brito [42] Portugal PET Mechanical properties and abrasion behaviour Rahmani et al. [43] Iran PET Mechanical properties Yang et al. [44] China PP Mechanical properties Janfeshan Araghi et al. [45] Iran PET Erosion resistance against sulphuric acid attack Islam et al. [46] Bangladesh PET Mechanical properties using PET as coarse aggregate Nikbin et al. [47] Iran PET Addition of light expanded clay Aattache et al. [51] Algeria HDPE Thermo-mechanical properties Safi et al. [52] Algeria PET Mechanical properties Benosman et al. [53] Algeria PET Diffusion of Chloride Ions Senhadji et al. [54] Algeria PVC Mechanical properties Benosman et al. [55] Algeria PET Physical and mechanical properties ...
... Conversely, Yin et al., Pereira et al. and Koo et al. did not report differences in compression strength with the addition of fibres, maybe because of the low dosage used (less than 1.5% per volume) [15,19,21]. This result was not influenced by fibre conformation type (line or diamond indentation). ...
... Borg et al. observed that higher fibre volumes provided better residual strength [26]. Yin et al. found differences in the post-cracking performance between line and diamond indented fibres [21]. While the first ones were pulled out the second ones were broken, which indicates that diamond indented fibres have better bonding. ...
Article
Valorization of waste plastic as concrete aggregates has become an opportunity. Some advantages are plastic waste recycling, consumption reduction of natural aggregates and improvement of concrete properties. This paper presents a review on addition of recycled plastic waste to cement composites and influence on their properties. Forty five international papers were selected from scientific peer-reviewed journals. The critical items analyzed were: plastic characteristics, mix proportion design and concrete properties. The last item includes fresh and hardened concrete properties, durability performance and thermal conductivity. Although some properties were negatively influenced by the plastics, this paper focuses on the variables that mitigate these effects. The improvement of insulation properties with plastic is widely analyzed, but further research is recommended. As conclusion, application of plastic waste would be useful on both, technical and environmental dimensions and this paper could be used as a helpful tool for studying and designing mortars and concrete composites with recycled plastic.
... Concluyeron que se incrementó la resistencia a la tracción en hasta 35 % y la tenacidad hasta 13 veces respecto del mortero sin fibras. Yin et al. (2015a) estudiaron fibras plásticas de polipropileno (PP) virgen y reciclado con textura, con un contenido de 4 kg/m 3 . Concluyeron que las fibras de material virgen resistieron más a la tracción y presentaron un módulo de Young inferior que el de las fibras recicladas. ...
... Se realizó una búsqueda bibliográfica de antecedentes sobre el uso de fibras plásticas de origen residual en hormigones. Luego, se propuso el diseño de las fibras (ancho, largo, espesor, morfología) y el tipo de material a emplear, considerando los valores más frecuentes de 17 publicaciones recientes (menos de 10 años de antigüedad), obtenidas de revistas científicas con arbitraje (Ochi et al. 2007, Kim et al. 2008, Won et al. 2010, Foti 2011, Fraternali et al. 2011, Pereira-de-Oliveira y Castro-Gomes 2011, Pereira-de-Oliveira et al. 2012, Foti 2013, Fraternali et al. 2013, Fraternali et al. 2014, Koo et al. 2014, Ghernouti et al. 2015, Spadea et al. 2015, Yin et al. 2015a, Yin et al. 2015by Borg et al. 2016. ...
... El comportamiento de las fibras puede optimizarse mediante tratamientos superficiales o conformado para mejorar la adherencia con el mortero (Yin et al. 2015a). Sin embargo, en estos ensayos se adoptó la forma recta y sin textura superficial. ...
Article
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The generation increase of solid waste represents a challenge for the development of new forms of recycling and reuse of materials. Plastics make up 10 % of solid waste worldwide and can be used to manufacture fibers for concrete and mortars. The aim of this paper was to design, and test recycled plastic fibers incorporated in cement mortars and compare their behavior with that of commercial fibers. For this, three dosages were elaborated: one standard mix, another mix with the designed fibers and a third one with commercial fibers. Test specimens were constructed and mechanical tests of ompressive and flexural strength were carried out. The mixture with the developed fibers achieved more than one and a half times the flexural strength of the standard mixture at 28 days, while only a 25 % increase in the case of commercial fibers mixtures was achieved. The compressive resistance also improved. It was concluded that the performance of the designed fibers was better than that of the commercial fibers, and that the use of fibers improved the properties studied with respect to mortars without fibers.
... They found that a 50% virgin and 50% recycled PP fiber blend had the same tensile strength as, but a greater Young's modulus than, virgin PP fiber. The properties of recycled polypropylene fibers in concrete for footpath applications were studied by Yin et al. [29], who concluded that the energy absorption of fiber reinforced concrete with a virgin PP to recycled PP ratio of 50:50 was higher than that using only virgin PP fiber due to the greater Young's modulus and tensile strength. The lowest energy absorption was found when using recycled PP fiber [30,31]. ...
... Moreover, Yin et al. [30] showed that the tensile strength of F prepared with a PP:RPP ratio of 100:0 was up to 25% lower than that of the F mixed with a PP:RPP ratio of 0:100. This is due to the addition of RPP in the specimens led to a lower molecular weight and shorter molecular chains as a result of higher crystallinity and different crystal sizes [29,30]. The compressive strength requirements for concrete footpaths, as specified by Austroads [41], and for rigid pavement, as specified by the Department of Highways, Thailand [42], are at least 25 [13], who concluded that incorporating 1 and 2% waste plastic fiber in the samples can increase compressive strength by 25 and 29%, respectively. ...
... compressive strength was found to decrease by about 4.4%. This is because the addition of RPP in the F results in decreased tensile strength and a decreased Young's modulus of F [29]. The maximum compressive strengths of 28 and 32 MPa FRC were found at a fiber content of 0.25% and a PP:RPP ratio of 100:0; these maximum compressive strengths values were 31.3 and 34 MPa, respectively. ...
Article
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The use of concrete in road construction has grown over the past decade due to the material’s great durability. However, concrete has poor tensile strength, ductility, and energy absorption. This paper aims to investigate the utilization of plastic waste, namely polypropylene (PP), to create a novel fiber to enhance the engineering properties of fiber reinforced concrete (FRC), an eco-friendly concrete that can reduce environmental problems. The 28-day design strengths of 28 and 32 MPa were used in this study because the compressive strength requirements for concrete footpaths and pavement specified by Austroads and the Department of Highways, Thailand, were at least 25 and 32 MPa, respectively. The fiber (F) was a mixture of virgin PP and recycled PP (RPP). The study used F contents of 0.25, 0.50, 0.75, and 1% by weight of cement and PP:RPP ratios of 100:0, 75:25, 50:50, 25:75, and 0:100. The compressive strength, flexural strength, leaching, and CO2 emissions savings of FRC were evaluated. Improvements in the compressive strength, flexural strength, and toughness of the samples with F were observed in comparison to the control concrete samples for all design strengths. All mixtures met the compressive strength requirements for concrete footpaths, except for F contents of 0.75 and 1% and a PP:RPP ratio of 0:100. By contrast, the 32 MPa FRC samples with F contents of 0.25 and 0.5% and all PP:RPP ratios met the requirements for rigid pavement. From an environmental perspective, the heavy metal contaminants of the 32 MPa FRC sample were within the allowable limits for all mixtures. Regarding incineration disposal, the maximum CO2 emissions savings of 28 MPa and 32 MPa FRC with an F content of 0.5% and a PP:RPP ratio of 0:100 were 1.0 and 1.11 kg CO2-e/m3, respectively. This research will enable plastic waste, traditionally destined for incineration and landfill disposal, to be used as a sustainable fiber in the construction industry.
... Another common way to increase the fiber-matrix bond strength of monofilament PP fibers is by twisting the straight fibers along their longitudinal axis, or indenting their surfaces (Figure 1b). Yin et al. [42] indicated that diamond surface indentations are more effective than line indentations in increasing the bond of macro PP fibers. [43], (b) surface-indented PP fibers [42], and (c) pre-treated PP fibers with microbiallyinduced calcite precipitation [44]. ...
... Yin et al. [42] indicated that diamond surface indentations are more effective than line indentations in increasing the bond of macro PP fibers. [43], (b) surface-indented PP fibers [42], and (c) pre-treated PP fibers with microbiallyinduced calcite precipitation [44]. ...
... The inconsistences among the available studies regarding the ability of PP fibers to increase pre-peak strength properties can be attributed to the variations in the fiber's dosage, geometry, and mechanical properties, as well as the characteristics of the concrete matrix. Studies have found that recycled PP fibers can deliver similar mechanical properties, while averting fiber degradation in concrete [42,132]. ...
Article
Full-text available
The concrete industry has long been adding discrete fibers to cementitious materials to compensate for their (relatively) low tensile strengths and control possible cracks. Extensive past studies have identified effective strategies to mix and utilize the discrete fibers, but as the fiber material properties advance, so do the properties of the cementitious composites made with them. Thus, it is critical to have a state-of-the-art understanding of not only the effects of individual fiber types on various properties of concrete, but also how those properties are influenced by changing the fiber type. For this purpose, the current study provides a detailed review of the relevant literature pertaining to different fiber types considered for fiber-reinforced concrete (FRC) applications with a focus on their capabilities, limitations, common uses, and most recent advances. To achieve this goal, the main fiber properties that are influential on the characteristics of cementitious composites in the fresh and hardened states are first investigated. The study is then extended to the stability of the identified fibers in alkaline environments and how they bond with cementitious matrices. The effects of fiber type on the workability, pre- and post-peak mechanical properties, shrinkage, and extreme temperature resistance of the FRC are explored as well. In offering holistic comparisons, the outcome of this study provides a comprehensive guide to properly choose and utilize the benefits of fibers in concrete, facilitating an informed design of various FRC products.
... O processo de formação de fissuras em concretos se dá por diferentes razões, podendo ser provenientes das restrições de movimentação, por vezes causando aumento de esforços internos de tração na mistura (CARINO; CLIFTON, 1995 O combate ao surgimento de fissuras pode ser feito de diversas maneiras em um composto cimentício (ABABNEH, 2001;YIN et al., 2015;JUAREZ et al., 2015). O uso de fibras se tornou um procedimento eficaz de reforço, com o intuito de superar as limitações de resistência à tração e aspecto frágil dos concretos convencionais (CHASIOTI; VECCHIO, 2017). ...
... Fibras de baixo módulo de elasticidade, como aramida, polipropileno e poliéster, não são recomendadas para matrizes com funções estruturais, pois o módulo de elasticidade do composto supera o do filamento, fazendo com que a fibra atue somente nos efeitos de segunda ordem (TANESI; FIGUEIREDO, 1999;YIN et al., 2015;YOUSEFIEH et al., 2017). Além disso, o período de atuação efetiva dos filamentos de baixo módulo de elasticidade permanece nas idades iniciais da mistura (SILVA, 2007). ...
... Fibras de baixo módulo de elasticidade, como aramida, polipropileno e poliéster, não são recomendadas para matrizes com funções estruturais, pois o módulo de elasticidade do composto supera o do filamento, fazendo com que a fibra atue somente nos efeitos de segunda ordem (TANESI; FIGUEIREDO, 1999;YIN et al., 2015;YOUSEFIEH et al., 2017). Além disso, o período de atuação efetiva dos filamentos de baixo módulo de elasticidade permanece nas idades iniciais da mistura (SILVA, 2007). ...
Article
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Analyzing the physical characteristics of the cementitious matrices, it is possible to highlight the shrinkage as one of the most influential in the durability. If not predicted or controlled, this has the potential to cause serious problems in systems, such as cracking. Due to the shrinkage effect of the matrix it is inevitable to encounter cracks in the early ages of the concrete due to the phenomenon of their volumetric variation. It is known that the addition of fibers affects the properties of the resulting composite, reducing its cracking potential. In this sense, this research evaluates the effects caused by the insertion of new and used polyester fibers in the drying retraction of concretes. The results of the compressive strength did not change with the addition of the polyester fibers in the reference concrete. By means of the restricted ring test it was possible to observe efficiency gains in the blends with the use of fibers, when it refers to the retraction by means of the reference matrix. The shrinkage stresses on drying were increased about twice with the inclusion of the fibrous reinforcements. It could be observed that the addition of recycled polyester fibers provided a reduction, about 80%, in the formation of cracks in the matrix when compared to the reinforcing effects in concrete with addition of the virgin fibers.
... Além disso, c, que é o comprimento crítico da fissura normalizado, é obtido pela relação ac/d. [5,16,42,54,68]. (0,09) (0,05) LOP = tensão correspondente ao limite de proporcionalidade; fR,1 = resistência residual à flexão correspondente a CMOD de 0,5 mm; fR,2 = resistência residual à flexão correspondente a CMOD de 1,5 mm; fR,3 = resistência residual à flexão correspondente a CMOD de 2,5 mm; fR,4 = resistência residual à flexão correspondente a CMOD de 3,5 mm. ...
... Entretanto, a adição das fibras tem efeito significativo no mecanismo de fratura dos cilindros de concreto, que passaram a romper de forma mais dúctil[13]. Mazaheripour et al.[41] também afirmaram que a presença de fibras discretas de polipropileno não resultaram em impacto significativo na resistência à compressão de concretos autoadensáveis reforçados com teores de até 0,3% de fibras, assim como Yin et al.[42] para concretos convencionais reforçados com teor de 4 kg/m3 de fibras discretas. A Figura 2.18 apresenta os resultados obtidos por Li et al. [16] sobre o efeito do conteúdo de fibras de polipropileno na resistência à compressão do concreto. ...
Thesis
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This work aims to present a comparative study of the mechanical performance and durability of concretes reinforced with discrete sisal and polypropylene macrofibers. Two cementitious matrices with different pozzolan material content were used. The both fibers were incorporated into fractions of 3 to 15 kg/m3 and were 51 mm long. Direct tensile tests were performed for the fibers, achieving equivalent stress values. For mechanical characterization of the composites, three-point flexural tests were performed under monotonic loading in accordance with the EN 14651 procedure. The behavior under cyclic loading was also investigated. To evaluate the fiber-matrix interaction, pull out tests were performed. The sisal fiber showed lower adhesion with the two matrices. All the composites with sisal and polypropylene fibers presented deflection softening behavior when subjected to flexural loads. In order to obtain similar flexural mechanical performance for both fibers, approximately twice dosage of sisal fiber was required. According to the classification proposed by fib Model Code, these fibers can partially or fully replace the conventional reinforcement at ultimate limit state. The durability of the composites was studied by accelerated aging process through wetting and drying cycles. The use of sisal fibers as reinforcement in the matrix with higher alkalinity showed degradation, while its incorporation into the matrix free of calcium hydroxide did not result in mechanical losses after the cycles. Concretes reinforced with polypropylene fibers did not present degradation caused by accelerated aging processes.
... The behavior of plain concrete in Fig. 8 is typical of brittle materials. It is possible to note a linear elastic zone before cracking followed by a rapid stress decrease with the CMOD increase, as confirmed by different research papers [35][36][37]. The flexural tensile strength of the unreinforced matrix was approximately 5% of the compressive strength at 28 days. ...
... All the composites presented a linear behavior until the appearance of the first crack, followed by a decrease in stress with the increase of CMOD. This behavior is known as deflection-softening, and is characterized by the development of a single crack, common in composites reinforced with the proposed dosages of discrete fibers [2,[35][36][37][38][39]. ...
Article
This investigation aims to compare the mechanical behavior of concretes reinforced with polypropylene and sisal fibers. Both fibers were 51 mm long and were incorporated in fractions of 3, 6 and 10 kg/m3 into the matrices. The composites were tested under three-point monotonic and cyclic flexural loads. Pullout tests were performed to study the fiber-matrix interaction. It was observed that the sisal fiber could provide the same level of residual strength as the polypropylene fiber, as long as the equivalence of the dosages of the fibers is taken into account. The composites were classified according to fib Model Code 2010 based on parameters obtained from flexural tests. The durability of the composites was studied by assessing the flexural behavior after wetting and drying cycles. Concrete reinforced with both fibers did not present mechanical losses after the cycles.
... Our production process includes melt-spinning and hot-drawing processes, where recycled PP plastic granules are extruded and hot-drawn into plastic fibers. Detailed production process of recycled PP fibers is covered in Chapter 4 and their performance in concrete is presented in other publications by the authors Yin et al. (2015a) and Yin et al. (2016a). This chapter focuses on the life cycle environmental benefits of production of recycled PP fibers compared to using SRM or virgin PP fibers to achieve equivalent reinforcement in concrete footpaths. ...
... The scope of this study does not include environmental impact at maintenance and post-use disposal stages of concrete footpath. Our study has shown that both plastic fibers and SRMreinforced concrete have similar performance, maintenance requirements, and life spans (Yin et al., 2015a;Yin et al., 2016a). Furthermore, it is assumed that the ...
... There are some applications where recycled polypropylene can be employed. For instance, Yin et al. [20] proposed the introduction of recycled fibers as a reinforcement of concrete; they compared the difference between virgin fibers, an actual alternative to steel meshes in concrete. Similar results were obtained for both kinds of fibers, therefore they can replace the steel meshes. ...
... The interaction between the matrix and the reinforcing fiber was analyzed by FTIR and FESEM. Finally, since these composites are intended for industrial applications where the hydrophobicity represents a handicap (i.e., automotive, construction materials, outdoor applications, etc.), the effect of the addition of compatibilized short hemp fibers in different percentages (10,20, and 30 wt%) on the water absorption properties of the rPP-based composites was studied. Finally, the composites' appearance was evaluated, and the color properties were assayed to get insights regarding the industrial applicability of the PP textile wastes recyclability as WPC materials. ...
Article
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This research reports the manufacturing and characterization of green composites made from recycled polypropylene obtained from the remnants of polypropylene non-woven fabrics used in the textile industry and further reinforced with short hemp fibers (SHFs). To improve the interaction of the reinforcing fibers with the recycled polymeric matrix, two types of compatibilizing agents (maleic anhydride grafted, PP-g-MA, and maleinized linseed oil, MLO) were added during melt-processing, the percentage of which had to remain constant concerning the amount of fiber loading to ensure complete reactivity. Standardized test specimens were obtained by injection molding. The composites were characterized by mechanical (tensile, impact, and hardness), thermal (DSC, TGA), thermomechanical, FTIR, and FESEM microscopy tests. In addition, color and water uptake properties were also analyzed. The results show that the addition of PP-g-MA to rPP was satisfactory, thus improving the fiber-matrix interaction, resulting in a marked reinforcing effect of the hemp fibers in the recycled PP matrix, which can be reflected in the increased stiffness of the samples. In parallel to the compatibilizing effect, a plasticizing effect was obtained by incorporating MLO, causing a decrease in the glass transition temperature of the composites by approximately 6 °C and an increase in ductility compared to the unfilled recycled polypropylene samples.
... The recycled fibers during the performance of the test demonstrated a good balance between tensile strength, elastic modulus and concrete bonding, thus producing brilliant post cracking performance. This research demonstrated the feasibility of using recycled fibers as reinforcement in concrete pavement [3] (Yin, et al., 2015). The basic guidelines for the design of a concrete reinforced with polypropylene-based fiber on road pavement, as it is applied in a real test section that rests inside a tunnel of the Marche-Umbria Quadrilatero, road empowerment project, Italy. ...
... The results of a six-month follow-up with the presence of real traffic loads, such as feedback to the design stage. The supervision covers the direct measurement of the level of tension inside the mold, as well as the acoustic measurement, it was a design solution for roads, especially within tunnels [4] (Nobili, Lanzoni and Tarantino, 2013). ...
Article
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The retraction affects the setting process and the useful life of the concrete with the appearance of fissures; in last year’s studies and methods have been generated to mitigate and control it with the use of different products and applications. The development of road infrastructure with the use of concrete as a rolling folder, requires methods to guarantee the durability and reduce the effects of the efforts incorporated by the use, climatic conditions, support base and restrictions of movement of the structure. To evaluate the effects of recycled synthetic polypropylene fibers in plastic retraction tests (ASTM C 1579), 3 mix designs were prepared with different ratios 58 gr., 116 gr., and 176 gr. of recycled and virgin synthetic fibers; the most significant and positive result to reduce fissures without affecting the resistance of concrete by bending and compression, was 0.50 mm without addition fibers, 0.10 mm and 0.15 mm with 176 gr. of virgin and recycled synthetic fibers. Finally, it can be concluded that adding a ratio of 4 kg per m3 allows good workability, in addition, the costs of the fibers are not representative compared to the high costs for future repairs.
... Mechanical properties (tensile strength and Young's modulus) of plastic fibers have significant influences on the postcracking performance of the plastic fiber reinforced concrete (Yin et al., 2015d(Yin et al., , 2016. In this research, tensile tests on plastic fibers were conducted according to ASTM D3822-07 (ASTM D3822, 2007). ...
... Table 4.3. Nevertheless, the mechanical properties achieved in 100% recycled PP fibers were shown adequate for the required postcracking performance in concrete as presented by the authors in their other publications (Yin et al., 2015d(Yin et al., , 2016. Melt blending 50% recycled PP with 50% virgin PP significantly improved tensile strength and Young's modulus compared to the 100% recycled PP. ...
... Yin et al. [20] PP Recycled PP fibers were studied and compared to virgin fibers, both with and without indentations. All the fibers produced a more ductile response and recycled fibers had a successful performance. ...
... Construction and Building Materials 295 (2021) 123420 [71,72] and 8 [73]. In this paper, equation 9 was obtained based on the results of eigth papers, four with plastic fibers [20,22,32,33] and four with plastic aggregates [37,41,43,48]. Fig. 10 shows that equations 7 and 9 are quite similar to each other, while equations 6 and 8 underestimate flexural strength. ...
Article
Many authors have previously reviewed the scientific literature about the use of plastic as aggregates and fibers in mortars and concrete. However, a full meta-analysis has never been conducted. Plenty of scientific data are available to be analyzed from published papers around the world. In this research, 435 experimental mixes using plastic as aggregates or as fibers were studied, belonging to 53 original papers. Scientific production related to these composites has had sustained growth since 2005. However, the largest amount of tests were carried out focusing mainly on the use of polyethylene terephthalate (PET), both as aggregates and as fibers. Thermo mechanical and technological properties were statistically analyzed, obtaining models for compressive strength, elasticity modulus, flexural strength and splitting tensile strength. As conclusion, this is the first general meta-analysis carried out about these composites and the main findings of this paper could be used by professionals and scientists, as well as an initial approach for elaboration of specific technical standards and codes.
... Due to the addition of fibers, mechanical properties, as well as impact resistance properties, improve especially under high-strain-rate impact loading, such as in the drop weight test. In a similar study, Hosseini et al. [10] and Yin et al. [11] utilized recycled polypropylene carpet fibers to improve impact resistance and energy absorption capacity. It was concluded that the recycled PP fibers significantly improved impact load from 71 to 418% for a fiber volume of 0.25-1.25%. ...
... It is a well-established fact that fibers of different types improve the mechanical properties (flexural strength, tensile strength, impact resistance, etc.) of plain concrete, particularly in post-crack regions [11]. In this present study, the effect of adding polypropylene fibers in concrete, with and without SBR latex at a constant dosage of 0.5% by weight of cement, was investigated [12]. ...
Article
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Improvements in tensile strength and impact resistance of concrete are among the most researched issues in the construction industry. The present study aims to improve the properties of concrete against impact loadings. For this purpose, energy-absorbing materials are used along with fibers that help in controlling the crack opening. A polymer-based energy-absorbing admixture, SBR latex, along with polypropylene fibers are used in this study to improve the impact resistance. Along with fibers and polymers, the effect of the size of aggregates was also investigated. In total, 12 mixes were prepared and tested against the drop weight test and the Charpy impact test. Other than this, mechanical characterization was also carried out for all the 12 concrete mixes. Three dosages of SBR latex, i.e., 0%, 4%, and 8% by weight of cement, were used along with three aggregates sizes, 19 mm down, 10 mm down, and 4.75 mm down. The quantity of polypropylene fibers was kept equal to 0.5% in all mixes. In addition to these, three control samples were also prepared for comparison. The mix design was performed to achieve a normal-strength concrete. For this purpose, a concrete mix of 1:1.5:3 was used with a water to a cement ratio of 0.4 to achieve a normal-strength concrete. The experimental study concluded that the addition of SBR latex improves the impact resistance of concrete. Furthermore, an increase in impact resistance was also observed for a larger aggregate size. The use of fibers and SBR latex is encouraged due to their positive results and the fact that they provide an economical solution for catering to impact strains. The study concludes that 4% SBR latex and 0.5% fibers with a larger aggregate size improve the resistance against impact loads.
... Most of the research has been conducted on different types of plastic waste like PET plastic [4,5,16,19,32], HDPE [33], expanded polystyrene (EPS) [23,34], polyvinyl chloride (PVC) waste [15,35], ethylene-vinyl acetate (EVA) [18]. Besides, in most cases, PP is used as a virgin fiber [36][37][38][39] or recycled fiber [40][41][42] or replaced as a partial replacement of fine aggregate [29,30] or as a percentage of cement mass [28]. A few studies have been conducted on PP plastic as coarse aggregate [31,43]. ...
... Flexural strength is decreased by 15.6% and 38.6% for 10% and 20% PP aggregate compared to 0% PP aggregate for the watercement ratio of 0.35. Again, for the water-cement ratio of 0. 40 [2,16,26,31,32]. Due to the hydrophobic nature and smooth surfaces of PP aggregates, the cement hydration reaction is restrained near the surface of PP aggregates. ...
Article
Reusing non-biodegradable plastic waste materials can be a viable solution towards minimizing the consumption of natural resources for construction purposes and reducing environmental hazards. Thus, this study inspects the potentialities of polypropylene (PP) plastic as coarse aggregate in concrete. This study aims to evaluate the mechanical and durability properties of PP concrete. It focuses mainly on workability, hardened density, compressive strength, modulus of elasticity (MoE), splitting tensile strength (STS), flexural strength, bond strength, temperature effect on compressive strength, shrinkage properties, and chloride ion penetration. The experimental work includes a varying percentage of PP aggregate as 10% and 20% of the volume of coarse aggregate and the water-cement ratios as 0.35, 0.40, 0.45, and 0.50. The experimental results reveal that the workability of concrete increased with the addition of PP aggregate into the mixture. Almost 5% and 10% density reduction can be achieved using 10% and 20% PP content, respectively. In terms of compressive strength, MoE, STS, and flexural strength, all the properties were decreased after incorporating PP aggregate into the concrete. At elevated temperatures, compressive strength decreased up to 10.8% and 34% at 100 °C and 200 °C, respectively. Besides, the shrinkage percentage increased with increasing the percentage of PP aggregate. However, the chloride ion penetrability of all PP concrete was fell in the moderate category. Regarding bond strength, 10% PP concrete exhibits better strength and a higher slip bearing capacity than the other percentages. Moreover, the PP concrete cylinders exhibited comparatively ductile failure than that of brittle failure of the reference concrete. Finally, to produce efficient and eco-friendly concrete, it is suggested to use PP aggregate up to 10% in structural concrete.
... To improve the mechanical properties of recycled aggregate concrete (RAC), scholars usually use concretemodification technology. These modification techniques mainly include removing the cement mortar on the surface of the RCA (physical method) [6][7][8], filling the pores and cracks inside the RCA with chemical solutions (chemical method) [9][10][11], and doping fibers to improve the pore structure of the interface transition zone (ITZ) [12][13][14]. Compared In engineering practice, commonly used fibers are steel fiber (SF) [15], polypropylene fiber [16], copper fiber [17] and basalt fiber [18]. ...
... The relationship between the macromechanical properties of SFRRC and the microscopic pore structure has not been discussed in detail, which requires further quantitative research. cracks inside the RCA with chemical solutions (chemical method) [9][10][11], and doping fibers to improve the pore structure of the interface transition zone (ITZ) [12][13][14]. Compared with the complicated operation process of physical and chemical methods, the method of doping fibers is more convenient. ...
Article
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A steel fiber-reinforced recycled concrete (SFRRC) is a porous material, and its macromechanical properties are affected by its microstructure. To elucidate the change rules and internal mechanisms of the mechanical properties of SFRRCs, the mechanical properties and failure modes of SFRRCs were studied at different water–cement ratio, replacement rate of recycled concrete aggregate (RCA), and steel fiber content. Moreover, the microstructures of the interface transition zones (ITZ) of the SFRRC specimens were tested by scanning electron microscopy and mercury intrusion, and the effect of the microscopic pore structure on the macromechanical properties of SFRRC was analyzed. The research results showed that an appropriate amount of steel fibers could reduce the size and number of cracks in the ITZ and improve the pore structure of an SFRRC. Based on the fractal dimension, porosity and other factors, the quantitative relationship between the macromechanical properties and microscopic pore structure parameters of SFRRCs was established.
... As reported by previous studies (Song et al. 2005; Page 2 of 20 Xu et al. Int J Concr Struct Mater (2018) 12:68 Mazaheripour et al. 2011;Kakooei et al. 2012;Cifuentes and Garcfa 2013;Nili and afroughsabet 2010;Yin et al. 2015; Karahan and Atis 2011;Zhang and Li 2013), when adding polypropylene fibers (PFs) into concrete matrix, the tensile and flexure strength, impact toughness, fatigue performance and post-peak ductility as well as durability of concrete are remarkably enhanced. Moreover, many experimental efforts have been devoted to investigating the stress-strain behavior of PFRC as well as steel-polypropylene hybrid fiber reinforced concrete (HFRC) material (Alhozaimy et al. 1996;Parveen 2013;Zhang et al. 2016;Hasan et al. 2011;Libre et al. 2011;Chi et al. 2014;Caggiano et al. 2016). ...
Article
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This paper presents results of an experimental investigation on the stress-strain behavior and damage mechanism of polypropylene fiber reinforced concrete (PFRC) under monotonic and cyclic compression. Fifty four specimens for different fiber volume fractions and aspect ratios were tested. Acoustic emission (AE) technique was used to monitor the damage progression. The damage mechanism of concrete was analyzed based on the AE parametric analysis. The results show that polypropylene fiber (PF) has a positive effect on the monotonic and cyclic behaviors of concrete, especially for the post-cracking branch. The toughness and ultimate strain are enhanced and the performance degradation in terms of elastic stiffness and strength is alleviated by the addition of PF. However, PF has little influences on the plastic strain, and the damage process of concrete is mainly driven by the envelope strain. Moreover, the effect of fiber volume fraction on the cyclic behavior of concrete shows more pronounced than that of aspect ratio. In addition, it is found from AE results that the damage, closely related to AE events, has a quick evolution just after the peak stress, with the AE hits having a concentrated release. The total amount of AE hits increases with increasing fiber volume fraction due to fiber pullout and sliding, while the concrete with fiber aspect ratio of 280 reaches the largest amount. Meanwhile, as substantiated by AE, the failure of PFRC shows an obvious shear mode, with shear cracks dominating the damage progression. Furthermore, a damage elasto-plastic model is developed to predict the monotonic and cyclic responses of PFRC and the prediction yields a fairly close estimation with experimental results.
... To a certain extent, the steel fiber shotcrete could reduce micro-cracks and prevent macroscopic cracks propagation [110][111][112][113][114][115][116][117]. Steel fiber is often used to improve the durability of the shotcrete [118][119][120][121][122][123]. ...
... Generally, FRCM with fibres added to control cracking have much higher tensile strength, abrasive resistance, impact resistance, ductility, toughness and fire resistance [13][14][15][16][17][18]. Among these fibres, polypropylene (PP) fibre is quite widely used due to its relatively low cost, good corrosion resistance, high effectiveness in crack control and high fire resistance [19][20][21][22]. ...
... In some cases, depending on the modulus of elasticity of the mixture, the reinforcement can have effect for 3 to 7 days. 25 Concerning the addition of polymer fibers to concretes, PP fibers stand out due to their versatility and usefulness. According to Ehrenbring, 26 the use of POL fibers has become more common, because it enables reuse of the primary material and improves sustainable bias. ...
Article
This study presents an investigation of a fiber‐reinforced concrete (FRC) with use of fibers of polypropylene, polyvinyl alcohol, and recycled polyester in the amount of 0.50%, seeking to analyze the impact of the fiber additions on mechanical properties, drying shrinkage, and cracking. Regarding flexural strength, a reduction of up to 25% of the value was observed for FRC. The residual strength of FRCs was increased values 20 times higher than the reference concrete. The addition of fibers also increased the void content of the matrices and, therefore, drying shrinkage of the reference matrix up to 74%. The fiber additions increased the internal tensile stresses of the FRC of up to 12.0 MPa. Besides the increase in resistance, the FRC presented formation cracks with openings 8 times smaller than the concrete.
... Thus, polymeric fibers are effective only when their modulus of elasticity is superior to that of the cementitious matrix. In some cases, depending on the properties of the mixture, the reinforcement may act for a few days (YIN et al., 2015). Tanesi and Figueiredo (1999) recommend the addition of low-volume fibers, varying from 0.10 to 0.30%. ...
Conference Paper
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Concretes with advanced technology become increasingly common in the construction industry through the development of mineral and chemical products, which guide the new generation of cementitious composites. However, even with those many advantages, the new concretes are still susceptible to drying shrinkage, being an inherent characteristic of these materials. If it is not mitigated, it can generate irreversible damages, like cracks, that undermine the durability of the structure. For this, in this research were used, in an isolated and hybrid way, polymeric fibers in order to impact on the cracking potential of the mixture. Besides the determination of the properties related to the shrinkage, the composites were characterized against the other physical and mechanical properties. The fibers were added with a content of 0.50% by volume, being polypropylene (PP), polyvinyl alcohol (PVA) and recycled polyester (POL). The fiber reinforced composites presented higher shrinkage due to drying when compared to the reference matrix, reaching deformations greater than 50 m/m. All the blends reached high cracking potential, with the samples containing PP and PVA fibers, which obtained the formation of the fissure later (14 days). It was also verified that the insertion of polymer fibers promoted the reduction of the axial compressive strength and the tensile strength in the flexion, in relation to the reference matrix. However, the use of PVA fibers did not promote the drop in tensile strength in the bending of the matrix. However, the toughness factor of the blends with fibers was higher than the reference concrete, increasing the results by up to 38 times.
... The fiber used in concrete reduces the absorption of water and, depending on the fiber type, slightly or significantly decreases the electrical resistance of it as compared to non-fibrous concrete [11]. Efficiency after cracking of various types of recycled polypropylene fibers obtained from industrial waste showed a good level of tensile strength, the Young modulus, of reinforced concrete with recycled polypropylene fibers, and these properties allow the use of recycled fibers in reinforcing the concrete of a column [12].Laboratory studies of seismic performance of reinforced concrete columns showed that effect of steel fibers is greater than the effects of hybrid fibers (polypropylene-metal fibers). In these concrete columns, the buckling performance of longitudinal reinforcements, ductility and energy dissipation seems more favorable [13]. ...
... Their results reported that ring shaped plastic fibers improved the first crack loading capacity of concrete. Yin et al. [26] observed that use of line and diamond indents recycled polypropylene plastic (PP) fibers in concrete improved the young modulus and tensile strength of concrete. The diamond indent PP fibers displayed superior bonding characteristics with concrete. ...
Article
Recycled fibers (RF) have demonstrated a sustainable solution in the generation of fiber reinforced concrete (FRC), but their flexural performance is still under study. This paper shows the flexural behavior of 15 FRC´s specimens with different aspect ratio and dosage of RF, to understand how these parameters affect their performance. In addition, 9 FRC´s samples with virgin fibers and 2 control samples (without fibers) were used as comparative elements. Workability, three-point bending and pull-out tests in combination with a count of fibers in the cracking section were developed. The results show a better flexural behavior of FRC of samples with high dosage and aspect ratio of RF, this combination generated similar or superior flexural performance with a better adherence in the concrete than those with virgin fibers. Data showed three principal problems with FRC´s with RF, a reduction of the workability in comparison with concrete without fibers, a lower quantity of fiber than samples with virgin fibers, and a non-uniform tendency in their mechanical performance.
... And the unreinforced beams have no postcracking (after the first peak load) performance. It is obvious that the area of the load-vertical displacement curve represents the energy absorbed by beams [32]. The energy absorbed by the unreinforced pervious concrete is in average 9 J. ...
Article
Pervious concrete has been widely used due to the environmental and stormwater management benefits. However, its susceptibility to cracking and low flexural strength limited the widespread use for vehicular traffic pavement. This paper focuses on the flexural behavior of pervious concrete beams reinforced by geogrids with different layer number at various positions. The influences of the embedded geogrids on effective porosity, strength and cracking behaviors are studied. The load-vertical displacement curves are obtained by four-point bending tests to describe the toughness and post-cracking performance of pervious concrete beams. Meanwhile, the acoustic emission (AE)and digital image correlation (DIC)techniques are used to monitor the internal fracture characteristics, strain fields and crack propagation. The experimental results indicate that the compressive strength and flexural strength of pervious concrete can be improved owing to the embedded geogrids. Notwithstanding an increased porosity is induced, the reinforced beams demonstrate significantly superior post-crack performance. Furthermore, the embedded geogrids in pervious concrete restrain the generation and propagation of the crack, resulting in a low strain field level as well as showing a short crack length and a small crack mouth opening displacement (CMOD). Embedding the geogrids at both one-third depth and two-thirds depth of the thickness provides the optimal performance.
... PP fibre is a lightweight material and has minor effect on mechanical performance and cracking control in comparison with metal fibres [22]. The mechanical properties of PP fibre-reinforced SCC (PPFRSCC) were slightly improved but the improvement was much less than that of SFRSCC. ...
Article
This paper reports a study on the use of nickel-titanium (NiTi) shape memory alloy (SMA), steel and polypropylene (PP) fibre as reinforcement in self-compacting concrete (SCC) to improve its load bearing capability and fracture resistance. The fibre’s type and its property between fibre and concrete matrix significantly influence the flexural performance of fibre-reinforced SCC (FRSCC), thus, the single fibre tensile property and the pull-out property between fibres and concrete matrix were studied prior to flexural strength test. In addition, in order to trace the failure and fracture development easily during the flexural strength test, the specimens tested in this study had a 25 mm notch. It is found that the NiTi fibre had 189 MPa tensile strength and 105 N pull-out strength, respectively. This is attributed to the smoth surface and the geometry of the NiTi fibre used (no hooked-end). The flexural strength and fracture development of FRSCC depend on the fibre type and fibre volume fraction used. It is found that the flexural strength of NiTi SMAFRSCC increased from 15 kN to 17.5 kN and NiTi SMAFRSCC specimens showed a considerable flexural residual performance without any fibre deformation and rupture. The steel and PPFRSCC samples also showed increased flexural strength with increase of fibre volume fraction but steel FRSCC has the larger values due to its higher fibre tensile strength.
... Liang et al. found that polypropylene fiber enhanced the bending performance of concrete and greatly improved the initiation toughness [21]. Nevertheless, the addition of polypropylene fiber declined the strength of concrete, and polypropylene fiber concrete was less effective in reducing dry shrinkage cracks [22]. It is not feasible for Qinghai area along with strong radiation and large temperature difference. ...
Article
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This paper mainly investigates the fracture parameters of Basalt Fiber Reinforced Concrete (BFRC) with various fiber lengths and dosages using Double-K fracture model. The model was developed by fracture criterion using ABAQUS Virtual Crack Closure Technique (VCCT), and the results of the model and experiments were compared. The basalt fiber with length of 6 mm and 12 mm was added into concrete in the dosage of 0.0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by volume of concrete, respectively. Concrete specimens were cast into three dimensions, i.e., 60 mm × 180 mm × 480 mm, 80 mm × 240 mm × 640 mm, and 100 mm × 300 mm × 800 mm. Then, three-point bending test was conducted on precast-notched beams. The load versus cracking mouth opening displacement (P-CMOD curve) was developed in order to evaluate cracking and breaking load. The initial fracture toughness and unstable fracture toughness were derived from the Double-K fracture model aimed to optimize the fiber length and dosage. The results showed that the initial fracture toughness and unstable fracture toughness increased first and then decreased with the increase in fiber dosage, and basalt fiber with length of 6 mm and dosage of 0.2% performed the best toughening effect on concrete. The comparison results showed that numerical simulation can better simulate the initiation and propagation of BFRC fractures and achieve the dynamic propagation process of fractures.
... Fibre mesh is a unique reinforcement material made through a specific which has high strength in longitudinal and transverse directions. At present, it is mainly used in the construction industry, including wall insulations, waterproofing, crack resistance, and repairing and retrofitting of existing concrete structures (Song et al. 2005, Yin et al. 2015, Li et al. 2017, Zhang et al. 2018b, Khan et al. 2019. Murtiadi et al. (2013) used sisal fibre mesh to strengthen the concrete wall, in which the fibre mesh was 15 mm away from the wall surface. ...
Article
The surface layer of military airfield pavements is prone to damage, including cracking, abrasion, and spalling. It is proposed to strengthen the pavement mortar layer by laying fiber mesh to solve these issues. In this study, three meshes of carbon fiber, aramid fiber, and basalt fiber were selected for surface reinforcement across six pavement slabs of 1.5m (length) × 1.5m (width) × 0.25m (height). The drop hammer impact test was carried out on the six pavement slabs. The test data were analyzed using impact times, crack development characteristics, and development models on the surface deflection as evaluation indices. The results show that the fiber mesh can effectively improve the impact resistance of concrete pavement slabs. Aramid fiber mesh best strengthened the pavement surface, whereas the basalt fiber mesh had the least strengthening effect. However, the mesh size has a negligible influence on the impact resistance of concrete pavement slabs. The effect of fiber mesh on improving the impact resistance of the concrete pavement slab corner was greater than that of the concrete pavement slab edge midpoint. Considering the performance and cost indicators, within the scope of the study, aramid fiber mesh is the most suitable for surface strengthening of airfield concrete pavement. ARTICLE HISTORY
... Results found that the flexural strength and compressive strength decreased with increase in temperature for all fiber types, with the optimum ratios of fiber addition of the specimens containing PP and GF being 0.5% by volume, and for PVA, it is between 0.5% and 1.5% by volume. Yin et al, [15] used different types of recycled polypropylene fibers from industrial waste and compared with virgin polypropylene fibers to study the performance of cracking in concrete. It was found to have a good tensile strength, Young's modulus and concrete bonding, thus good performance for post-cracking. ...
Article
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Fire is reflected as one of the most serious possible risks for buildings and constructions. The main objective of this research is to investigate the effect on the performance of beams reinforced concrete under and without fire conditions by adding waste polypropylene fibers (WPPF) with two variable values of volume fraction. Six beams with different volume fraction of WPPF ratio were tested to study the behavior of the beams when exposed and not exposed to fire conditions. Three of these beams were prepared with volume fraction of WPPF ratios 0%, 0.5%, and 1% to test under two-point loads without exposure to fire, while the other beams were prepared with same conditions to test after exposure to fire. The results showed that the reinforced concrete beams without fibers suffered significant reduction in overall performance and mechanical properties, when subjected to fire for enough time to reach elevated temperatures (400 C⁰). Both 0.5% and 1% of WPPF ratios didn't affect the flexural capacity before the fire, however, reduction in compressive strength occurred. On the other hand, the fiber improved the tensile strength and the first cracking load, and also reduced the loss in compression strength after the fire. Finally, the recommended optimal ratio of WPPF is not more than 0.5%.
... Therefore, it is essential to study the impact of PP fibers on the concrete. However, the existing researches about the PP fiber-reinforced concrete mainly focused on the compressive strength, ductility and elastic modulus [20,[27][28][29][30][31], and little research was about the porosity and the strain development [32,33]. This necessitates the objective of this article to conduct a systematic study of waste fiber-reinforced tailings recycled aggregate concrete. ...
Article
The purpose of this study was to assess the performance of introducing polypropylene (PP) fibers into recycled aggregate concrete containing iron ore tailings (TRAC). Thus, we prepared four different concretes, including natural aggregate concrete (NAC), recycled aggregate concrete (RAC), TRAC and fiber-reinforced tailings recycled aggregate concrete (TRAC-PP) series. PP fibers were used as supplementary material at different percentages (0.3%, 0.6%, 0.9% and 1.2%) and compared with NAC, RAC and TRAC. The cubic compressive strength, axial compressive strength and splitting tensile strength were analysed. The digital image correlation technique was used to monitor the strain development of concrete under compressive loading. Besides, the nuclear magnetic resonance technique was applied to evaluate the pore structure. The testing results showed that the use of recycled coarse aggregate (RCA) led to the reduction of strength of concrete, but this strength loss can be compensated by adding iron ore tailings (IOTs) to concrete. The addition of PP fibers to TRAC was significantly in the splitting tensile strength, but not obvious in the compressive strength when the supplementary percentage of PP fibers was lower than 0.6%. The failure pattern of TRAC-PP1.2 was relatively ductile and its cracks were relatively tortuous and fine. RAC had the highest total pore contents. Addition with IOTs and PP fibers to RAC significantly decreased the total pore contents. Recycling of RCA and IOTs would reduce the environmental impact and economic cost. Finally, the concrete with 30% RCA, 30% IOTs and 0.6% PP fibers can be considered as the most appropriate concrete.
... Energy absorption capacity of fibre reinforced concrete was better assessed using fracture based studies and CMOD measurements were used to evaluate the stress crack width relationship of concrete (Shi, 2015;Gopalaratnam et al., 1991). The fracture process of fibre reinforced concrete involves crack bridging of fibres followed by fibre pullout or rupture leading to a crack control mechanism. ...
Article
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The present study investigated the mechanical characteristics of different types of steel fibre substituted high strength concrete. Influence of steel fibre volume fraction and its complex profile characteristics on the strength properties of various fibre reinforced concretes had been systematically studied in slender concrete beam sections. Reinforcing efficiency of concrete incorporating four types of steel fibres having the same aspect ratio with varying fibre profile-single hooked ends, crimped, double hooked ends, and kinked had been experimentally analyzed in flexural bending and fracture studies. Test results showed higher flexural post peak toughness (23.48 N-m) and fracture toughness (39.62MPa√mm) for double hooked steel and crimped steel fibres substituted concretes. Steel fibre reinforced concretes containing double hooked and kinked geometry exhibited higher overall performance index. Also, high volume steel fibre substitutions (1.5% V f) in slender concrete beams showed improved fracture toughness characteristics.
... Besides, it will save the significant cost of money to recycle and dispose of polymer wastes, prevent the environment from pollution, and save energy. Various research have been conducted on virgin PP fiber [28][29][30] or recycled PP fibers [31,32] or replacement of PP as fine aggregate [25] but a few research have been conducted on PP plastic as coarse aggregate [27]. Therefore, the present study focuses on the physical and mechanical properties of concrete containing polypropylene (PP) plastic as coarse aggregate in terms of workability, hardened density, compressive strength, modulus of elasticity, tensile strength, modulus of rupture, ultrasonic pulse velocity as well as a cost-sensitive analysis. ...
Article
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The application of waste materials in concrete is getting more popular in the concrete industries as it can reduce the associated costs and environmental impacts. The present study investigates the performances of concrete while incorporating polypropylene (PP) plastic, derived from waste plastic products, as a partial replacement of natural stone aggregate (SA) and burnt clay brick aggregate (BA). The main variables include the percentage of PP aggregate (PPA) (0%, 10 %, 20 %, and 30 %), water-cement ratio (0.45 and 0.55), and types of aggregate (SA and BA). Results are presented in terms of workability, hardened density, compressive, tensile strengths, modulus of rupture, modulus of elasticity (MoE), ultrasonic pulse velocity (UPV), and cost analysis. Furthermore, empirical equations are proposed for predicting different properties of concrete; especially, predicting compressive strengths from the UPV values. Results indicated that the slump value increased with increasing the percentage of PPA. Concrete with 10 % PPA exhibited higher compressive strength, modulus of rupture, and splitting tensile strengths, even, higher than that of the control stone aggregate concrete (SAC) and control brick aggregate concrete (BAC). The UPV values varied with aggregate types and PPA content. Both the compressive strength and the UPV values decreased with the increasing percentages of PPA from 10 to 30. Furthermore, SAC exhibited higher compressive strength and UPV values compared to BAC. A good correlation was found between the compressive strength and the UPV values for concrete with PPA. From the cost sensitivity analysis, it was observed that concrete containing 10 % PP content had the highest strength over cost ratio compared to the control and other PPA concrete. Therefore, it is recommended to use up to 10 % PPA either with stone aggregate or brick aggregate for structural concrete. Finally, this study will open new opportunities for producing green concrete by using non-biodegradable waste plastic materials.
... is is mainly because the polypropylene fibers restrain the pores diameter to enlarge [25], further making the whole structure of the concrete more complete [9,20,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. ...
Article
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This paper aimed to explore the performance of concrete with iron tailings sand modified by polypropylene fibers under aggressive environment. Three kinds of concrete (ordinary concrete, concrete with iron tailings sand (ITS), and concrete with ITS modified by polypropylene fibers) were exposed to drying-wetting cycles in 5% Na2SO4 solution for 28, 56, 84, 112, and 140 days. The performance, such as pores distribution, crack width, corrosion products, mass variation, expansion variation, compressive strength, flexural strength, and the diffusion of sulfate ion were measured at regular time intervals during the whole exposure period to describe the associated evolution laws. The results show that, in the process of the corrosion of sodium sulfate solution, the formation of gypsum and ettringite (AFT) has an important impact on the harmful pores (>0.1 μm), cracks, mass variation, expansion variation, compressive strength, and flexural strength of the three concrete. Polypropylene fibers can refine the pores development and inhabit the crack development of the concrete with ITS, further alleviating the rate of sulfate ion attack on concrete and the rate of increase of corrosion products, so that the mass variation, the expansion variation, and the reduction of compressive strength and flexural strength can be limited effectively. Furthermore, in the concrete with ITS modified by 0.1% polypropylene fibers, the content of sulfate ions diffused is always the lowest.
... The RPF and PPF fibers help to sew up the microcracks and delay their propagation, which prevents the appearance of macro-cracks. From this, Fig. 3 Variation of flexural strength for NSC and HSC according to fiber content type fiber reinforced HSC concrete exhibits better mechanical characteristics after cracking due to the high adhesion between fibers and concrete compared to NSC concrete (Setti et al. 2020, Yin et al. 2015. ...
Article
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An experimental study was undertaken to evaluate the performance of recycled polypropylene fiber (RPF) in concrete. The RPF materials were recycled from woven bags and used in concrete at various volume fractions corresponding to 0.1%, 0.2%, and 0.3%. Two different classes of strength, corresponding to normal and high strength concrete, were investigated. Fiber was used as substitution of coarse aggregate in concrete. The dosage of fiber was used at relatively lower dosages to avoid altering fluidity and to limit the reduction in coarse aggregate content. On the other hand, a commercial polypropylene fiber (PPF) was used at equivalent dosages than RPF for comparisons purposes. Test results indicated that optimized RPF volumes can secure comparable mechanical performance than those obtained with commercial PPF. On the other hand, the use of both fiber types resulted in lower compressive strength (10 to 20%), higher flexural strength (up to 27%), and lower elastic modulus (by 16%). Furthermore, the use of RPF type reduced the drying shrinkage (6 to 10%) of normal and high strength concrete types and increased the permeable pore void of both concrete types.
... Cominoli et al. [16] investigated the possibility of replacing steel mesh in the external plate of a precast panel with synthetic fibres; they found that a minimum cover is no longer needed when fibre reinforced concrete is used, and moreover the panel weight and transportation costs are lower than for a normal precast panel. Further investigation into the post-cracking performance of recycled synthetic fibres in concrete considered the variations between virgin PP fibre and recycled PP fibre under a crack mouth opening displacement [17]. The load at both fibrous concrete cases reached a peak load of 20 kN and then dropped instantly to a range of 0.1 to 0.5 kN; the load then increased until the displacement reached 1.5 mm. ...
Article
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Adding fibers to concrete helps enhance its tensile strength and ductility. Synthetic fibres are preferable to steel ones which suffer from corrosion that reduces their functionality with time. More consideration is given to synthetic fibres as they can be sourced from waste plastics and their incorporation in concrete is considered a new recycling pathway. Thus, this work investigates the potential engineering benefits of a pioneering application using extruded macro polyfibres in concrete. Two different fiber dosages, 4 kg/m3 and 6 kg/m3, were used to investigate their influence based on several physical, mechanical and microstructural tests, including workability, compressive strength, modulus of elasticity, splitting-tensile strength, flexural test, CMOD, pull-out test and porosity. The test results revealed a slight decrease in the workability of the fibre-reinforced concrete, while all the mechanical and microstructural properties were enhanced significantly. It was observed that the compressive, splitting tensile and bonding strength of the concrete with 6 kg/m3 fibre dosage increased by 19.4%, 41.9% and 17.8% compared to the plain concrete specimens, respectively. Although there was no impact of the fibres on the modulus of rupture, they significantly increased the toughness, resulting in a progressive type of failure instead of the sudden and brittle type. Moreover, the macroporosity was reduced by the fibre addition, thus increasing the concrete compressive strength. Finally, simplified empirical formulas were developed to predict the mechanical properties of the concrete with fibre addition. The outcome of this study will help to increase the implementation of the recycled plastic waste in concrete mix design and promote a circular economy in the waste industry.
... hardening phenomenon. Meanwhile, the previous study by Yin et al.[55][56][57] reported that unmodified PP fibres only had a minor influence on the flexural strength of concrete. On the other hand, PP fibres mainly improved the toughness and postcracking performance of concrete rather than the flexural strength. ...
Article
To improve the bonding strength between polypropylene (PP) fibres and concrete, this study investigates a new method of modifying the surface by grafting hydrophilic groups and silane groups on PP fibres. Characterisation of fibre modification, fibre pullout performance from concrete, and flexural behaviour of fibre reinforced ultra-high performance concrete (UHPC) were studied. From the Fourier transform infrared (FTIR) and water contact angle measurements, both the hydrophilic groups and silane groups demonstrated successful and efficient surface grafting on the PP fibres, which helped to improve the bonding behaviour of the grafted fibres. The silane groups and hydrophilic groups grafted PP fibres showed significant improvement in the bond behaviour, in which the pullout forces were approximately 3.0 and 1.6 times of unmodified PP fibres, respectively. The energy absorption of the modified fibres, estimated from the pullout tests, showed an increase by 121% and 80% for silane groups and hydrophilic groups, respectively. The silane groups grafted PP fibre reinforced UHPC showed outstanding toughness and deflection-hardening performance, which increased by 97% as compared to those of unmodified fibres. The flexural performance of 27 kg/m 3 silane groups grafted PP fibre reinforced UHPC was comparable with the 78 kg/m 3 steel fibre reinforced UHPC.
... The post-cracking phase followed, during which the plastic fibres began to make their contribution and the deformation energy was dissipated by the fibres with the consequent remaining load, which remained constant up to a CMOD of nearly 4.5 mm, as depicted in Figure 5. This same behaviour was observed by many other researchers using different types of commercial or recycled plastic, and with different amounts of plastic fibre [14,41,44,57]. Figure 6a shows the load-deflection graphs, while Figure 6b shows the initial segments of the graphs obtained by linearly interpolating the forces between the values of 20% and 60% of the peak force, where the first break occurred, as dictated by the UNE 83510: 2004 standard, which allowed us to calculate the toughness and the toughness index. The behaviour of the four mixtures was generally similar, wherein there was a first phase where the force increased until it reached its maximum value (peak value), and where the first crack occurred in the specimen. ...
Article
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For many decades, researchers have been working on finding innovative and sustainable solutions to address the enormous quantities of plastic waste that are produced every year which, after being collected, are transformed into energy, recycled, or sent to landfills. Giving a second life to plastic waste as a material to be incorporated, in the form of macro-fibres, into concrete, could be one such solution. The purpose of this study was to analyse the mechanical and physical behaviour of the hardened concrete reinforced with macro plastic fibres (RPFs) obtained from food packaging waste (FPW) discarded during the packaging phase. By varying the quantity of macro-fibres used, physical and mechanical properties such as compressive strength, modulus of elasticity, flexural strength, and toughness were evaluated. It was observed that, although the presence of macro plastic fibres reduced the mechanical resistance capacity compared to that of traditional concrete, their contribution proved to be of some importance in terms of toughness, bringing an improvement in the post-crack resistance of the composite material. This innovative mixture provides a further impulse to the circular economy.
Article
A comprehensive experimental study was conducted to explore the fracture characteristics of basalt fiber–reinforced fly ash geopolymer concretes (FAGCs) with different fiber contents (0.025%, 0.05%, 0.1%, 0.15%). The fracture behaviors of the basalt fiber–reinforced FAGCs, such as load-crack mouth opening displacement curve, fracture toughness, fracture energy, crack propagation length, were investigated by three-point bending tests, and their strengthening mechanisms were explored by scanning electron microscopy. In addition, the Mori–Tanaka homogenization (MTH) method was introduced to analyze the elastic properties of the basalt fiber–reinforced FAGCs. It was found that the addition of basalt fibers improved the peak load, fracture toughness, and fracture energy of the basalt fiber–reinforced FAGCs, and the most significant improvements were noticed in the concrete with the basalt fiber content of 0.05%. Moreover, a decrease in the crack length of the basalt fiber–reinforced FAGCs was observed before the load level of the post-80% peak load. The elastic properties of the basalt fiber–reinforced FAGCs were analyzed based on the MTH theory, and numerical results were found to be in good agreement with experimental findings.
Article
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This paper presents a focused comparative case study considering the influence of natural and synthetic fibers on the fresh and mechanical properties of concrete. Locally sourced 19 mm long sisal fibers from sisalana leaves and manufactured polypropylene fibers were incorporated in a normal strength concrete matrix with fiber volumetric contents of 1%. After describing the measured aggregate characteristics, mix designs, and fresh concrete properties, several destructive and non-destructive tests on hardened concrete were undertaken. The former included compression tests on cylinders and flexural tests on prismatic samples, and the latter included ultrasonic pulse velocity and rebound number tests. The workability of sisal-fiber reinforced concrete was generally lower than the nominal concrete and that provided with polypropylene fibers by about 20%, largely due to the hydrophilic nature of the natural fibers. Test results showed that the presence of sisal fibers can improve the compressive strength by about 6%, and the tensile strength by about 4%, compared with the non-reinforced counterpart. This was due to the sisal fibers storing moisture that was released gradually during hydration, helping with the strength development. The concrete with polypropylene had virtually identical properties to the reference concrete. In addition to fresh and mechanical properties, environmental impacts associated with the production of fiber and concrete were also identified and discussed. Based on the assessments from this paper, overall, from the two fibers investigated, the sisal fiber showed more promising results, indicating that natural fibers can be a more sustainable alternative to plastic fibers, providing a good balance between workability and strengths.
Article
Macro-synthetic fiber-reinforced iron ore tailings (IOT) concrete is an environment-friendly building material featured by recycling IOT and improving performance of IOT concrete due to fiber incorporation. In this study, the mechanical properties of macro-synthetic fiber-reinforced concrete incorporating IOT were investigated. Two different replacement ratios of IOT (i.e., 0% and 50%) and six types of macro-synthetic fibers at 1.0 vol% were adopted to investigate the effects of IOT, aspect ratio, elastic modulus, and tensile strength of macro-synthetic fibers on mechanical properties of concrete. The results indicate that the concrete with IOT for natural sand (NS) replacement in 50 wt% demonstrates no loss in compressive strength and a minor loss of 7.67% in fracture energy, but the incorporation of IOT lowers splitting tensile strength and limit of proportionality, especially the splitting tensile strength with a decrease of 18.50%. The splitting tensile strength, equivalent flexural tensile strength, residual flexural tensile strength, and fracture energy were notably improved by adding macro-synthetic fibers. Experimental results using Tukey test and Student's t test demonstrated that the fiber aspect ratio was more effective in improving equivalent flexural tensile strength, residual flexural tensile strength, and fracture energy than the elastic modulus and tensile strength of fibers, and the residual flexural tensile strength fR,4 was enhanced by 146.34% when increasing the fiber aspect ratio from 36 to 60.
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The aim of this research is to establish the fracture properties of high performance concrete (HPC) containing hybrid – basalt (B) and polypropylene (P) fibres. The experimental investigation consisted of tests on cubes, beams and notched prismatic specimens made of plain HPC and fibre reinforced HPC with 1% and 2% of basalt and/or polypropylene fibres. Extensive data on the compressive and tensile splitting strength, flexural behaviour, as well as fracture energy are determined and analyzed. The experimental investigations show that HPC with hybrid B/P fibres display a more ductile behaviour compared to that of plain HPC. The results of the bending tests revealed extended post-peak softening behaviour. The shape of the descending branch depended on the mechanical properties of the fibres, and volume content used. The results illustration the positive effect of high modulus basalt and low modulus polypropylene fibres on HPC fracture energy growth. Moreover the results indicate that a combination of fibres may contribute more effectively to increasing the flexural strength, flexural toughness and fracture energy than using a single type of fibre.
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Due to the elevating demand to replace the conventional cement concrete with any other building material, there has been a continuous effort to promote the properties of geopolymer concrete. The objective of this paper is to reduce the brittleness of geopolymer concrete. This research paper goes for exploring the impact of high and low young’s modulus fiber in geopolymer concrete made of M-sand. Mix proportion of various materials is based on the Rangan’s proposed Mix design. Geopolymer concrete used in this investigation is the Fly ash – Ground Granulated Blast Furnace Slag blend based. Concoction of NaOH solution and Na2SiO3 solution is used as the alkali solution. Sine 80 percent of the source material is flyash, the specimens are exposed to heat curing. Fresh property and hardened characteristics like workability, ductility factor, compressive, split tensile, flexural and impact strength are assessed in this study. Significant increase in the engineering properties is observed with respect to both the fibers. This work unveils lot of potential in the vicinity of Geopolymer concrete.
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The modern deep cement mixing wall requires a thinner wall thickness due to limited space in urban areas. A soil-cement column can have the characteristics of a brittle failure pattern and low tensile and flexural strength due to the high cement content (10%-20%); thus, to ensure the serviceability and stability of a restricted wall when subjected to horizontal loads, jute fiber and polyvinyl alcohol (PVA) fiber are utilized as reinforcement to improve the flexural and fracture performance of the soil-cement column. In this research, the effect of fiber addition on the flexural performance and fracture mechanics of cemented soil were evaluated by the indicators of peak flexural strength, residual flexural tensile strength, crack mouth opening displacement (CMOD), and energy absorbing capacity. In addition, the durabilities of unreinforced and fiber-reinforced specimens were studied by comparing the flexural strength under wet-dry cycles and observing the plastic shrinkage cracks in the early age. The results showed that the inclusion of fibers significantly improved the flexural performance and fracture energy of soil-cement, and it was shown that the fiber reinforcement effectively restrained the formation and propagation of plastic shrinkage cracks in the early age and reduced the flexural strength loss under wet-dry cycles.
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Fibre-reinforced concrete (FRC) allows reduction in, or substitution of, steel-bars to reinforce concrete and led to the commonly named structural FRC, with steel fibres being the most widespread. Macro-polymer fibres are an alternative to steel fibres, being the main benefits: chemical stability and lower weight for analogous residual strengths of polyolefin-fibre-reinforced concrete (PFRC). Furthermore, polyolefin fibres offer additional advantages such as safe-handling, low pump-wear, light weight in transport and storage, and an absence of corrosion. Other studies have also revealed environmental benefits. After 30 years of research and practice, there remains a need to review the opportunities that such a type of fibre may provide for structural FRC. This study seeks to show the advances and future challenges of use of these polyolefin fibres and summarise the main properties obtained in both fresh and hardened states of PFRC, focussing on the residual strengths obtained from flexural tensile tests.
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This paper describes an experimental study, which has been lacking to date, into the mechanical properties of cementitious composites incorporating granules and fibres from recycled Reinforced PVC (RPVC) banners. A detailed account of over 140 tests on cylindrical, cubic and prismatic samples tested in compression and flexure, with up to 20% replacement of mineral aggregates, is given. Based on the test results, the uniaxial properties of selected recycled materials are examined in conjunction with a detailed characterisation of the RPVC granule size and geometry. Experimental measurements using digital image correlation techniques enable a detailed interpretation of the full constitutive response in terms of compression stress-strain behaviour and flexural stress-crack opening curves, as well as key mechanical parameters such as strength, elastic modulus and fracture energy. It is shown that the mechanical properties decrease proportionally with the amount of RPVC. For each 10% increment of volumetric replacement of mineral aggregates, the compressive strength is halved whilst the flexural strength is reduced by about 30% compared to their conventional counterparts. The reduction in strength is counterbalanced by an improved ductility represented by a favourable post-peak response in compression and an enhanced flexural softening and post-cracking performance. Smaller particles, with a relatively long acicular or triangular geometry, exhibited better behaviour as these acted as fibres with improved bond properties in comparison with intermediate and large size granules. The test results and observations enable the definition of a series of expressions to determine the mechanical properties of cementitious materials incorporating RPVC and other waste plastics. These expressions are then used as a basis for an analytical model for assessing the compressive and tensile stress-strain response of such materials. Validations carried out against the tests undertaken in this study, as well as from previous investigations, indicate that the proposed expressions and the developed constitutive model offer reliable representations for practical application.
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Although polymers were originally seen as an option to replace other materials due to their physicochemical properties and low cost, they have become an environmental problem due to poor final disposal practices. For these reasons, in the presented investigation, impact of waste polypropylene (wPP) from bottle caps and waste polyethylene (wPE) from bottles, on mechanical characteristics of polymer mortars were observed. Mortars were produced with unsaturated polyester resin at 20% ratio and silica sand at 80% ratio. Sand was replaced with the wastes at three different ratios as 1, 2 and 3 wt% and sizes as 0.71, 1.4 and 2.38 mm. Observations exhibited improvement about 27% for compressive strength when adding wPP particles; 30% on the compressive deformation (adding wPE) as well as 82% on the flexural deflection (adding wPP). Nevertheless, flexural strength and the elasticity modulus of polymer mortars decline by depending on the increment in content and sizes of the wastes used. That is highly connected to morphologies observed by SEM of the fractures polymer mortars.
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To study the effect of multisize polypropylene fibers on the compression characteristics of concrete cubes, ten sets of polypropylene fiber-reinforced concrete test pieces were designed and fabricated to obtain their stress–strain curves and mechanical parameters at different ratios of coarse and fine fibers. Results for the cubes with multisize fibers were better than for those with to single-size ones. Based on test results, an improved statistical damage constitutive model for such a material is proposed.
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Concrete is one of the leading composite materials for construction, therefore the identification of strategies aimed at reducing its environmental impact is crucial for greening the building industry and achieving the Sustainable Development Goals set by the United Nations. One way to reduce this impact involves the opportunity to recycle waste materials as fiber in concrete reinforcement, thus following the circular economy principles. The feasibility of using different waste materials in Recycled Fiber Reinforced Concrete (RFRC) is attracting practitioners’ attention. Through a systematic literature review, the paper analyzes the academic literature on concrete reinforcement using recycled fibers. The main goal is to provide an exhaustive analysis of the phenomenon with rigorous and reproducible research criteria. Eventually, 194 articles were analyzed. RFRC is a research topic, which is rapidly growing over the last years and scholars’ attention is focused both on engineering aspects, through experimental studies testing the composite mechanical properties, and environmental sustainability considerations. From the analysis, emerged that even though the relevance of the construction industry and, as a consequence, of concrete in the global transition toward sustainability it is widely recognized, there is a gap in investing the potential of RFCR in addressing the triple bottom line of it. Finally, it emerged a great research potential in exploring how recycled fibers may be part of a construction industry oriented and inspired to circular economy principles.
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Concrete is the most used construction material in the world. Consequently, the mass extraction of virgin materials required for concrete production causes major environmental impacts. With a focus on promoting sustainability, numerous research studies on incorporating waste materials to replace virgin substances in concrete were undertaken. Despite this vast volume of published literature, systematic research studies on these sustainable concrete mixes that inform various stakeholders on current research trends, future research directions, and marketability options products are seldom conducted. This paper presents a decade review on sustainable concrete with a focus on virgin materials being replaced with waste materials. It aims to inform researchers of current research trends and gaps in the research area of waste material use in concrete. The review also identifies key parameters that restrict the marketability of these sustainable concrete products. The three-step research methodology involves a bibliometric assessment, a key review of selected waste materials, and an interview with a panel of experts focusing on impediments towards the transition of sustainable concrete products into the industry market. Bibliometric assessment was based on 1465 research publications in which five key materials (plastic, glass, fly ash, slag) and construction and demolition waste were selected for the review. The interview was conducted with ten industry experts to discuss the industry limitations in the commercial establishment of materials. The review of existing knowledge and the findings on sustainable concrete presented in this paper provide directions for both research academics and industry stakeholders to systematically focus on sustainable concrete products that are market-ready.
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The present study has examined the two-lift concrete pavement (2LCP) fracture and mechanical behavior by casting the Roller Compacted Concrete (RCC) as the bottom lift and the conventional or fibrous Portland cement concrete (PCC, FPCC) as the top lift. To this end, the three-point bending test was carried out on notched beams by considering different thicknesses for both layers. Results showed that fibers had no positive effects on the compressive and flexural strength, but improved the post cracking behavior considerably. Compared to full-depth RCC/PCC, 2LCP specimens had similar flexural strengths, but an increase in the FPCC top-layer thickness increased the fracture energy noticeably.
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La inclusión de plásticos, en forma de fibras o gránulos, en la elaboración de hormigón produce beneficios tales como el reciclaje de plásticos residuales procedentes de la actividad industrial y urbana; la sustitución de agregados naturales; y las mejoras en propiedades del hormigón, tales como control de la fisuración, menor densidad y aumento de las condiciones aislantes. Sin embargo, es necesario garantizar sus propiedades mecánicas de modo de asegurar la función estructural. El objetivo de este trabajo fue determinar el estado del arte sobre el tema y obtener el punto de partida para investigar aplicaciones de plásticos en paneles estructurales de hormigón armado. Para ello se realizó una revisión de publicaciones en revistas indexadas. Los resultados se muestran atendiendo a los siguientes tres ítems: tipos de plásticos utilizados y procesos mecánicos para preparar los agregados plásticos; diseño de las mezclas cementicias; y ensayos y propiedades determinadas sobre los plásticos, y sobre el hormigón fresco y endurecido. Posteriormente, se analizaron y discutieron los resultados obtenidos. Se concluyó que el PET es uno de los tipos de plásticos más empleados en hormigones y que su uso es recomendable en un amplio rango (0,5 -29,9%) con una mediana de 3,6 %. Pudo verificarse que el agregado de fibras de plástico consigue un buen control de fisuración y mantiene propiedades mecánicas del hormigón dentro de límites aceptables. Se detecta que las propiedades aislantes del hormigón han sido poco estudiadas, constituyéndose en la línea experimental de investigación que dará continuidad a este trabajo.
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Plastic macro fibres, inclusive of virgin and recycled plastic fibres, are becoming more popular in the construction of concrete footpaths, precast panels and shotcrete mine tunnels. In particular, the use of recycled plastic fibres has become increasingly attractive due to their low cost and sustainability. However, due to their production and service history, the recycled plastic fibres normally have lower mechanical properties than the virgin plastic fibres. Therefore, the feasibility of using recycled plastic fibres in concrete may be in doubt. This research assessed reinforcing effects of the recycled Polypropylene (PP) fibre and compared it with those of the virgin PP fibre. Crack mouth opening displacement (CMOD) and round determinate panel test (RDPT) were carried out to assess the post-cracking behaviours of the recycled PP fibre reinforced concrete. The results showed that the recycled PP fibre produced by the same process as the virgin PP fibre obtained lower tensile strength but higher Young’s modulus than the virgin PP fibre. Although the recycled PP fibre had lower tensile strength, in the CMOD and RDPT the recycled PP fibre showed comparable reinforcement to the virgin PP fibre owing to its higher Young’s modulus.
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The offshore oil and gas industry will use and discharge large quantities of chemicals into the marine environment during operational activities, with some of those chemicals considered hazardous. Chemical substitution, as part of the environmental regulatory regime, has been advocated as a simple and effective tool to reduce inputs of hazardous substances to the environment. In 2007 the UK National Plan was introduced, to prioritise into four groups and subsequently phase out in stages the most hazardous substances used and discharged during offshore oil and gas operations. Level 1 substances categorised for phase out in 2010 were virtually eliminated from discharge between 2006 and 2012 and there was a significant decline in discharge of substances at Level 2 to 4 over the same period. The discharge of substitutable substances had been reduced to less than 5 tonnes at most production installations by 2012. More than 91% of this discharge is contributed by corrosion inhibitor, scale inhibitor, demulsifier and water clarifier formulations. The discharge of corrosion inhibitors accounted for the largest contribution to UK National Plan Level 2 substitutable substance discharges, and they appear to be the type of product with the fewest options found for substitution. This implies that a finite discharge of substances from these groups will continue to require formal justification beyond the target date, as occurred for Level 1 substances after the 2010 target date. The overall figures for substitutable substance discharges from 2006 to 2012 suggest that the introduction of the UK National plan with prioritisation of substances for substitution and ongoing encouragement of operators and, indirectly, suppliers to work towards reduction goals for substitutable substances is resulting in a reduction in discharges and contributing to their ultimate phase out. The next few years will be particularly challenging as the deadline for the phase-out of discharges of substitutable substances included in OSPAR Recommendation, 2006/3 is 1 January 2017 and, in addition, by 2018 all chemical substances used offshore will need to have been registered under the EC REACH Regulation. The approach described in this paper illustrates the benefits of a prioritised strategy for chemical substitution and an ongoing dialogue between the industry and regulator. A continuing case by case dialogue with offshore operators and suppliers will be essential to ensure that alternative technical solutions are trialled and options for substitution are investigated at the earliest stage.
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Concrete is an indisputable material for the construction of various types of structures in the modern advancement of civil infrastructures. Concrete is strong in compression but weak in tension and shear. To eliminate those problems, the introduction of fiber was brought in as an alternative to developing concrete in view of enhancing its tensile and shears strength as well as improving its ductile property. Hence, the purpose of this study was to investigate the mechanical behavior of concrete reinforced with macro (structural) synthetic fibers. To determine these properties experimental work was carried out. Four batches of concrete were cast: one with no fibers and the remaining three with three different volume fractions fibers of 0.33, 0.42 and 0.51%, respectively. Concrete specimens (cubes, prisms and beams) were cast to determine the mechanical behavior such as compressive, tensile, shear strength and stress-strain relationships. Test results showed that macro synthetic fiber enhanced the compressive strength insignificantly. However, macro synthetic fibers at 0.33, 0.42 and 0.51% volume fractions improved the tensile strength by at least 10, 15 and 14%, respectively, compared to the control specimen. Similarly the ultimate shear strength was increased significantly by at least 15, 45 and 65% for macro synthetic fibers of 0.33, 0.42 and 0.51% volume fractions, respectively, compared to the control beams. The failure of plain concrete specimens was sudden (brittle) for both the tensile and shear strength tests. However, the concrete reinforced with macro synthetic fibers showed more ductile behavior compared to the plain concrete. Macro synthetic fibers improved the ultimate strain value by at least 50, 60 and 60% for macro fibers of 0.33, 0.42 and 0.51% volume fractions, respectively.
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With the increase in the general awareness on waste management, recycled plastic fibres reinforced concrete has attracted widespread attention. However, the production of recycled plastic with sufficient mechanical properties is still a major challenge. This research focuses on improving the tensile strength and Young’s modulus of recycled polypropylene (PP) fibres produced through hot drawing process. The mechanical properties of the mixture of 50% recycled PP and 50% virgin PP were compared with 100% virgin and 100% recycled plastic fibres. The 100% recycled PP fibres achieved tensile strength of 310 MPa and Young’s modulus of 620 MPa. The combination of recycled (50%) and virgin PP (50%) showed significant improvement in Young’s modulus (800 MPa). Tensile strength was also found to increase to 360 MPa. The crystalline structure and crystallinity degree of the PP fibres were also studied to explore the effects of hot drawing process on the mechanical properties of the plastic fibres. The hot drawing process increased the degree of crystallinity from around 50% to over 80%. Both α- and β-form crystals were found in all the plastic fibres, but recycled PP fibre contained more β-form crystals than the virgin PP fibre, resulting in lower Young’s modulus.
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This study investigated the utilization of polyethylene terephthalate (PET) bottle fibre recycled as fibre-reinforced renders mortar. The fibres were obtained by simple mechanical cutting from bottles. Investigation was carried out on cement-lime mortar samples. Different volumes of fibres, i.e. 0%, 0.5%, 1.0% and 1.5%, were introduced in dry mortar mixes. Specifically, the mechanical properties as flexure, compressive strengths and mortar toughness were measured. The results indicate that the incorporation of PET fibres significantly improve the flexural strength of mortars with a major improvement in mortar toughness. The maximum volume of PET fibre for a desired workability was 1.5%.Research highlights► Polyethylene terephthalate bottle fibre recycled as fibre-reinforced renders mortar. ► Fibres obtained by simple mechanical cutting from bottles. ► PET fibre incorporation increases the mortar flexural strength and toughness. ► The optimum volume of PET fibre incorporation for a desired workability is 1.5%.
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Satisfactory structural performance of Fibre Reinforced Shotcrete (FRS) in applications such as tunnel linings is dependent on an ability to support load after cracking. At present, both beam and panel specimens are used to measure the post-crack flexural capacity of this material. Although these tests have been widely used to develop improved fibres and FRS mix designs, the relationship between performance data produced in beam and panel tests is unclear. This investigation was therefore undertaken to examine possible correlations in behaviour between beam and panel specimens and determine which was the most appropriate type of test for a given FRS application. La performance structurale du béton projeté renforcé de fibres (BPRF) pour des utilisations telles que le support et le renforcement de tunnels dépend de l'aptitude du matériau à supporter les charges après fissuration. À l'heure actuelle, des échantillons de poutre ou de petites dalles sont utilisées pour mesurer la résistance en flexion après fissuration du BPRF. Même si de nombreux essais ont été réalisés pour développer de meilleures fibres et améliorer la composition des mélanges de BPRF, la correspondance entre les résultats obtenus par l'essai sur poutre et ceux sur dalle est ambiguë. La présent étude a donc été réalisée afin d'examiner les relations possibles entre les résultats des essais sur dalle et ceux sur poutre pour déterminer la configuration d'essai la plus appropriée pour une utilisation donnée de BPRF.
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We describe a method that can be used to produce concrete-reinforcing PET fiber from used PET bottles. Using this method, the concrete and PET fibers are easily mixed at a fiber contents as high as 3%. The primary characteristic of the PET fiber is that it is easy to handle. The issue of concern in the development of PET fiber is its alkali resistance; however, we encountered no problems when using the fiber in normal concrete. The wetting tension of PET was found to be lower than that of PVA but higher than that of PP. No toxic gas was generated during a combustion test of the PET fiber. We describe two example applications: a gateway support at Hishikari Mine, Japan, and the pavement of bush roads.
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The size effect on the tensile strength of concrete is investigated experimentally for the case of equi-biaxial tension. Tests of tensile strength under uniaxial tension were carried out for comparison using four-point bend beams. For measuring the biaxial tensile strength, the ASTM C1550 test and the biaxial flexure test were examined. To study the size effect, unreinforced circular plates of three different sizes are tested, with 13 specimens per size. The size effect on the equi-biaxial tensile strength is found to be stronger than it is on the uniaxial tensile strength, and to exhibit the characteristics of the deterministic Type I size effect. The detailed experimental procedure and the results are reported in this paper. Under the assumption that a distinct continuous crack develops only after the peak load, the approximate law of size effect is derived from the stress redistribution due to a boundary layer of cracking. The analysis leads to a deterministic Type I size effect.
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Mixed plastic and paper waste products were subjected to different processing schemes that yielded end products of different slendemess and fineness levels. These end products were evaluated as discrete reinforcement systems in concrete. The dosages of recycled products were adjusted in light of their geometric attributes to yield fresh concrete mixtures with desirable workability, homogeneity, and air content. The effects of discrete reinforcement systems of recycled and virgin origins on concrete mechanical, physical, and durability characteristics were examined. The results indicated that discrete reinforcement systems derived from abundantly available waste streams can, at proper dosages, yield positive reinforcing effects in concrete. The improvements in restrained shrinkage crack control and impact resistance were particularly significant and comparable to those of virgin fibers.
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Logging of aspen (Populus tremuloides Michx.) forests on public grazing land in west central Alberta creates a mosaic of habitat types that may alter cattle (Bos taurus) use of these landscapes. We used an extensive network of field plots and global positioning system (GPS) collars deployed on cattle within four experimental pastures, each containing a mix of uncut forest, clear cut forest, partially harvested areas, and in-block haul roads, to examine habitat preferences during mid-summer grazing in 2008 and 2009. We also examined the effect of two cattle stocking rates the first year. Although cattle removed similar amounts of forage in all habitats, GPS data indicated cattle spent more time in uncut forests, and avoided clear cuts and in-block haul roads during both years, patterns that remained consistent under either livestock stocking rate tested. Observed patterns of habitat use were attributed to conservative cattle stocking rates consistent with or greater than those allocated on publicly grazed forest land in Alberta, combined with specific habitat attributes. Preferred use of uncut forest was attributed in part to favorable forage quality, which was positively associated with cattle utilization (standardized β = +0.13) among plots. Although forage use by cattle of plots also increased with forage biomass (β = +0.33), sharp increases in biomass following clear cut logging appeared to be offset by reductions in forage use associated with increased slash cover (β = −0.12) and sapling density (β = −0.11), both of which may have impeded cattle access. As a result, forage removal remained similar among habitats. Finally, cattle use of forage decreased with increasing distance from water (β = −0.22), highlighting the importance of ensuring reliable access to water across forested pastures to prevent localized overuse. Overall, the reduced time cattle spent in clear cut habitats coupled with similar forage removal suggests that under low cattle stocking rates, grazing can be compatible with deciduous forest management in the region.
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Polypropylene (PP) fibers have been widely used to reinforce concrete footpaths as an alternative to steel mesh. The reinforcing effect of the PP fiber is directly proportional to its tensile strength and Young modulus. This research explored the feasibility of using an improved melt spinning and hot drawing process to produce virgin and recycled PP fibers of high mechanical properties in an industrial scale. Commercial grade granules of virgin PP, recycled PP and HPDE were mixed in different proportions in preparing five different types of fibers. All the fibers obtained high tensile strength and Young modulus. A relationship between the structural parameters and mechanical properties was then established. It was observed that the melt spinning and hot drawing process formed both α-form and β-form crystals in the PP fibers, and significantly improved crystallinity from about 50% to 80%. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41866.
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We elucidated how polypropylene, jute, and water-soluble polyvinyl alcohol fibres mitigated the increase in pressure in fibre-reinforced high-performance concrete (HPC) heated to elevated temperatures. The vapour pressures of the water inside the HPC specimens reinforced with the three types of fibres were compared with the saturated vapour pressure of water in the specimens. Permeability tests were also performed on specimens of the fibre-reinforced HPC at 100, 200, 300, and 400 °C. The heated control, jute, and WSPVA specimens exhibited increased permeabilities. Although the permeabilities of the three specimens heated below 200 °C did not significantly change, the permeability of the control specimen heated above 200 °C was four times higher than its permeability prior to heating. The permeability of the jute specimen heated higher than about 200 °C was four to nine times higher than its permeability prior to heating. The jute specimen exhibited the highest permeability of all the heated specimens. The permeability of the WSPVA specimen heated above 200 °C was three to six times higher than its permeability prior to heating. The normalised permeabilities of the WSPVA and jute specimens were smaller than those of the PP specimen. The WSPVA fibres also resulted in the development of pressure-induced tangential spaces (PITS) at the fibre-concrete interface at temperatures of 50–90 °C, which is the temperature range at which WSPVA fibres dissolve in water and above which solid WSPVA becomes increasingly flexible. The straw-like structure of the jute fibres prevented the vapour pressure within the concrete from increasing.
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This paper focuses on the study of the influence of flowability and wall-effects of the formwork in the orientation pattern of macro-plastic fibres. In order to identify the preferential orientation of fibres caused by the geometry of slabs, pairs of specimens drilled from PFRC slabs with different width/length - ratio are tested using the multidirectional double punch test (MDPT). The results show that plastic fibres tend to be oriented parallel to the walls or surfaces of the formwork and perpendicular to the flow direction for a free surface flow. The side walls slightly redistribute the fibre orientation, as the transverse dimension of the slabs is reduced. Additionally, a computed tomography (CT-scans) was, for the first time, successfully applied to assess the amount of macro-plastic fibres as well as its distribution and orientation in a prismatic core.
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This paper deals with an experimental study on the mechanical properties of recycled polyethylene terephthalate fibre-reinforced concrete (RPETFRC) and its durability in an aggressive seawater environment. A Portland limestone cement-based concrete with a 0.38 water/cement ratio is used to cast cubic and prismatic specimens, in association with two different PET fibres obtained through extrusion of recycled PET flakes (R-PET). Some of these specimens were conditioned in the Salerno harbour seawater for a period of 6/12 months. Compressive strength and four-point bending tests are performed in order to investigate the mechanical properties of such RPETFRCs. Comparison of the present results and those in the literature for air-cured RPETRCs highlights the influence of the analysed R-PET fibres on the mechanical properties of concretes showing different water/cement ratios and binders. The given results for seawater-cured specimens demonstrate that such a curing condition slightly modifies the first-crack strength and markedly reduces the toughness of the RPETFRCs examined in the present work.
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This paper focuses on the study of the structural response of hyperstatic concrete flat suspended slabs reinforced only with structural plastic macro-fibres. First, the experimental program is described and then the results obtained are presented. The slabs tested maintained a high load level after cracking showing a ductile behaviour with great stress redistribution capacity. Next, the tests were simulated by means of a finite element software with constitutive models according to the specifications of RILEM and the Spanish Structural Concrete Code (EHE). The numerical results in terms of load/mid-span deflection were compared with the experimental results. The predictions provided by the codes and guideline models clearly overestimated the experimental results, which suggests the need to review the constitutive models used for plastic fibre-reinforced concrete.
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Spraying of concrete is a well-established and economical alternative to conventional casting techniques. It is widely applied in repair/reinforcement of building elements, rock consolidation and for the construction of temporary or permanent tunnel linings. Sprayed concrete (shotcrete) may be reinforced with fibers, steel rods or steel meshes to increase its mechanical performance under bending. In wet spraying, the concrete is premixed with water and then sprayed by means of compressed air. The fibers are added to the fresh concrete and then sprayed together with it. Because of their high elastic modulus and tensile strength often steel fibers are used for such applications. Recently, macro-synthetic plastic fibers have been proofed to be a suitable non-corroding alternative.
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There have been a great number of studies aiming to improve the mechanical qualities of concrete material which is a basic component of reinforced concrete bearing systems. Attempts to reinforce the concrete through fiber addition have an important place among these studies. This study is an experimental research on the mechanical features of hybrid fiber added concretes which are obtained using steel fibers and polypropylene (PP) fibers together in certain proportions. Test specimens consist of 180 cylindrical samples (150 × 300 mm) and 90 prismatic (150 × 150 × 750 mm) beams produced in C40 concrete class. The specimens were exposed to temperatures ranging from room temperature to 100, 200, 400, 600 and 800 °C in a certain order following their cure periods of 7, 28 and 90 days. It was observed that hybrid fiber addition has a significant contribution into the compressive strength, flexural strength and energy absorption capacity of the concrete. Significance of hybrid fiber addition was put forward for the increase in ductility of the concrete which displays a brittle behavior when forced to bending.In the experimental studies with a numerous test specimens, losing of data due to some reasons and being unable to receive data was considered as a problem to be solved. Therefore, a fuzzy-genetic model was suggested to predict not only the experimental gaps, but also the untested value ranges of experimental parameters. Model was taken consideration in three different applications and it showed a satisfactory performance in predicting data.
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The existing design code for Concrete Industrial Ground Floors, TR34, by the Concrete Society states that “Macro synthetic fibres provide some post-cracking or residual moment capacity but with significantly lower performance than steel fibres. They are not known to be used in industrial floor construction”. This paper presents results of an ongoing investigation undertaken by the authors concerning the mechanical and physical properties of fibre reinforced concrete ground slabs at an industrial scale. This paper focuses and presents results concerning the punching shear failure of a 6.00 m × 6.00 m × 0.15 m synthetic fibre reinforced ground supported slab. The paper demonstrates clearly the methodology adopted and the infrastructure used throughout this investigation. The presented results show clearly that the punching shear failure values obtained in this investigation are comparable to values reported for the steel fibre slabs under similar conditions. This work could potentially question the validity of the above statement in TR34. The significance of this research also is in the size of the slab investigated, as there is very limited work, if any, reported within the literature.
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This paper presents an experimental campaign in which concrete pipes were manufactured using plastic fibres as the sole reinforcement material. In this regard, it has been demonstrated that the use of plastic fibres is compatible with pipe production systems, and that, when subjected to the crushing test (CT), plastic fibre reinforced pipes yield strength classes that are attractive in terms of the growth of this material in the concrete pipe industry. Moreover, the results obtained from both the characterisation of the material and the mechanical behaviour of the pipes have been used to verify that the Model for the Analysis of Pipes (MAPs) is an appropriate tool for the design of such pipes. Finally, this paper presents a direct design methodology which was used to establish the firsts design tables for fibre reinforced concrete pipes presented in the scientific literature. This methodology can be used to estimate the strength requirements of the fibre reinforced concrete needed to reach the strength classes set out in EN 1916:2002, without having to resort to the CT as an indirect design method.
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We study the alkali resistance and the flexural response of a cement-based mortar reinforced through polyethylene terephthalate (PET) strips obtained through hand cutting of ordinary post-consumer bottles. On considering 1% fiber volume ratio and different strip geometries, we show that the analyzed reinforcing strips owe remarkable alkali resistance and are able to markedly improve the toughness of the base material. Comparisons are established with the outcomes of a recent study on a similar reinforcement technique of a cement-lime mortar.
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The present paper describes the results of an experimental investigation on the performances of concrete specimens reinforced with either steel or macro-synthetic fibres under three-point bending. Steel fibres are often used to improve the flexural toughness of concrete and are used in various structural applications while synthetic fibres are more often used to reduce crack opening due to shrinkage. Macro-synthetic fibres have been proposed more recently with the aim of creating an alternative to steel fibres in structural applications but their use is still limited.In the tests performed, specimens cast with the same concrete mix, but containing different dosages of either steel or macro-synthetic fibres, were used and compared. In general steel fibres were more efficient in increasing the toughness of concrete than macro-synthetic fibres, even though their results were significantly more scattered.Test results were used to calculate the parameters of stress-crack opening relations via inverse analysis using a cracked hinge model. This numerical model provided results, in terms of force-Crack Mouth Opening Displacement (CMOD) curves, in very good agreement with the experimental data.
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This study investigated the long-term durability performance of recycled polyethylene terephthalate (PET) fibre-reinforced cement composites. Specifically, chloride permeability, repeated freeze–thaw, and various chemical environment tests were conducted. Five types of chemical environments were considered, alkaline, salt, CaCl2, sulfuric acid, and sodium sulfate. Recycled PET fibre-reinforced cement composite was not different from plain concrete in terms of chloride permeability. The repeated freeze–thaw test results showed excellent endurance characteristics of recycled PET fibre-reinforced cement composite. Recycled PET fibre-reinforced cement composites showed reduced compressive strength in alkaline and sulfuric acid environments. However, recycled PET fibres and recycled PET fibre-reinforced cement composites were largely unaffected by salt, CaCl2, and sodium sulfate environments.
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In this study, the reinforcing fibers were constructed with three different geometries, i.e., embossed, straight, and crimped, from waste polyethylene terephthalate (PET) bottles and used them to control plastic shrinkage cracking in cement-based composites. Pullout tests evaluated how the fiber geometry and fraction by volume (0.1–1.00%) affected the rate of moisture loss and controlled the plastic shrinkage cracking characteristics. The fiber geometry and fraction by volume did not affect the total moisture loss or moisture loss per hour; the moisture loss per hour exceeded 0.5kg/m2/h in 5h after casting, causing plastic shrinkage cracking. However, increased fractions of recycled PET fiber resulted in improved control of the plastic shrinkage cracking. At a fraction of 0.25%, the plastic shrinkage was reduced, but no further improvements were observed when the fraction of fiber was increased to 0.5%. Fiber geometry also affected the control of plastic shrinkage cracking up to a fiber fraction of 0.25%.
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With the growing interest in the use of synthetic fibre-reinforced concrete in the construction industry, attempts to clarify its performance have become important. The characteristics of various synthetic fibres and the behaviour of concrete reinforced with each of these fibres are discussed here. The present paper reviews current research concerning the performance of synthetic fibre-reinforced concrete based on polyethylene (PE), polypropylene (PP), acrylics (PAN), poly(vinyl alcohol) (PVA), polyamides (PA), aramid, polyester (PES) and carbon reinforcements which are considered to be promising for the development of cementitious composite materials.
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Plastic shrinkage cracks may occur even when standard precautions have been taken, which may impair the durability and serviceability of concrete structures. One way to prevent such cracks is by adding short fibers to the concrete mixture. The aim of this work is to evaluate the effect of the addition of synthetic fibers, such as polypropylene, glass, nylon and PET fibers in concrete cracking control. An experimental program was conducted to investigate plastic shrinkage cracking in small thin slabs, by varying the fiber volume fraction of fibers in the mixtures. Concluding remarks and a few recommendations are given at the end of the work.