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This paper presents an experimental study conducted to investigate the effect of fiber reinforcement on the mechanical properties and shrinkage cracking of recycled fine aggregate concrete (RFAC) with two types of fiber—polyvinyl alcohol (PVA) and nylon. A small fiber volume fraction, such as 0.05% or 0.1%, in RFAC with polyvinyl alcohol or nylon f...
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... can be explained by the higher air content of R-Ny01, which can have an effect on the compressive strength and modulus of elasticity of concrete. In addition, the modulus of elasticity was dependent on the density of concrete [31], which was also proved by the reduction in density of R-Ny01 as presented in Table 6. Additionally, the results exhibited that the relative strength of R-0 was lower than N-0 by 10.1%; further, in cases of fiber-reinforced RFAC, the relative strength of all specimens was lower than N-0, from 8.8% up to 17.5%. ...
Context 2
... can be explained by the higher air content of R-Ny01, which can have an effect on the compressive strength and modulus of elasticity of concrete. In addition, the modulus of elasticity was dependent on the density of concrete [31], which was also proved by the reduction in density of R-Ny01 as presented in Table 6. Table 7 lists the splitting tensile strength and the flexural strength for concrete specimens at 28 days. ...
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Citations
... To study the flexural strength of recycled fine aggregate concrete Nam et. al. [16] used polyvinyl alcohol and nylon fibers in the concrete. Fibers were used in dosages of 0.05% and 0.1%. ...
The effect of binary blending of recycled aggregates and nylon fibers on the workability and flexural strength of concrete has been investigated in this work. An equal dosage of recycled aggregates from demolished wastes and conventional aggregates was used with 0.5 water cement ratio in preparing a mix of 1:2:4. Nylon fibers were used from 0% to 2% with an increment of 0.25% by weight of cement to reinforce the concrete. The slump cone test was determined for all nine batches of the concrete. Workability was observed to reduce with an increase in the content of nylon fibers. Flexural strength was evaluated by testing three prism specimens of 150mm x 150mm x 500mm size in each batch. A comparison of test results with control concrete (0% nylon fibers) and recycled aggregate concrete (with 50% recycled aggregates and without fibers) showed that nylon fibers helped in overcoming the loss of flexural strength due to the addition of recycled aggregates. The optimum dosage was recorded as equal to 1.5% with an increase in strength equal to 19.13% and 52.45% in comparison to conventional and recycled aggregate concrete.
... However, the tensile strength of RCA concrete will be adversely affected by the excessive content of waste PP fiber [16]. Das C S et al. believe that this is due to the high stress generated at the end of the fiber and shorter fibers in the cleavage process, resulting in a decreased RCA concrete tensile strength [17][18][19][20]. In addition, the optimal fiber addition rate of RCA concrete will also change with the replacement rate of RCA. ...
... In addition, the optimal fiber addition rate of RCA concrete will also change with the replacement rate of RCA. Nam J [18] found that adding polyvinyl alcohol and nylon fiber into RCA concrete is helpful to improve the interface bonding ability between cement matrix and RCA, thus improving the dynamical performances of RCA concrete. Thwe Thwe Win [21] found that introducing FM fibers, particularly an FM with a 5 mm diameter and 10 mm length, in the mortar increased both the tensile and flexural strengths. ...
To effectively recycle waste petroleum products and construction waste, recycling polypropylene fiber (RPF) and recycled aggregate can be mixed into concrete to make RPF recycled coarse aggregate (RCA) concrete. In this study, the RPF recycled from a polypropylene (PP) packaging belt was used as the test material and manually cut into the shape required for the experiment. The effects of RCA and RPF on the tensile mechanical behavior of concrete are researched. The failure modes and constitutive relationship of the specimens under axial tension and splitting tension are further investigated. The results show that the axial tensile strength of RPF RCA concrete first increased and then decreased with the increase in fiber volume content, and was the largest when the fiber volume content was 1.5%, and its strength increased by 21.14% compared with that of recycled concrete. Its lifting rate relative to recycled concrete is between 13.14–21.41%. The change trend of axial tensile strength with the substitution rate of RCA is that it decreases with the increase in substitution rate, and the substitution rate decreases by 9.64% when the substitution rate is 100% compared with 0%.The peak strain first increased and then decreased with the increase in fiber volume content, and the maximum fiber volume content was 1.5%, which increased by 28.19% compared with that of recycled concrete. The peak strain first increased and then decreased with the increase in fiber length-diameter ratio, and the maximum length-diameter ratio was 47.85, which increased by 18.22% compared with that of recycled concrete. The peak strain increased with the increase in the replacement rate of RCA, and the peak strain at 30%, 60% and 100% was 96.22%, 102.45% and 118.09% when the replacement rate was 0%, respectively.
... This is mostly due to the localized limitations established by PETF reinforcement, which effectively regulate the development of fractures prior to the emergence of obvious macro cracks. These fibres also withstand the tension pressures created in the beam specimens, increasing the flexural strength of the concrete [43]. ...
Concrete is currently the most frequently used material in the building sector due to its favourable properties. However, the proliferation of waste poses a significant environmental problem. Over the past three decades, researchers have explored the use of construction and demolition waste (CDW) as well as plastic waste as aggregates, binders, and fibres in construction materials. This approach has emerged as a notable solution to address environmental and economic challenges. The objective of this research is to assess the impact of polyethylene terephthalate fibres (PETF) on the behaviour of self-compacting concrete (SCC) with recycled fine concrete aggregates (RFCA). Natural fine aggregates (NFA) were used as a substitute for RFCA at different mass fractions (0–100%). Additionally, four volumetric fractions (Vf) of PETF (ranging from 0.3% to 1.2%) were added, and the findings revealed an improvement in the flexural strength and modulus of elasticity of the composite material obtained. However, as the Vf content of PET fibres and RFCA increased, the compressive strength decreased, negatively affecting water absorption by immersion and capillary water absorption. Using 100% RFCA and 1.2% PETF enhanced the modulus of elasticity and flexural strength of recycled self-compacting concrete (RSCC) by up to 25% and 9%, respectively.
... Akono et al. [17] examined the microstructure of concrete with RFA and found that the porosity of C-S-H gel in RFAC accounts for 56% of the total porosity. Nam et al. [18] reported that RFAC exhibits 26% and 10% lower tensile and compressive strengths, respectively, compared to concrete with NFA. Hassan et al. [19] investigated the mechanical specifications of concrete incorporating RFA and NFA, highlighting higher reductions in compressive strength compared to tensile and flexural strengths. ...
The incorporation of waste materials in concrete is currently a practical solution to solve certain environmental concerns. Because of the property degradation of the produced concrete owing to the addition of waste materials, using pozzolans in the concrete mix can help improve the mechanical performance of recycled concrete. Therefore, in this research, the mechanical specifications of recycled concrete were evaluated at different volume fractions of recycled fine aggregates (RFA) replacing natural fine aggregates (NFA). In addition, the impact of adding colloidal nano-silica particles on the performance of conventional and recycled concretes was investigated. Various parameters comprising compressive strength, pulse velocity, splitting tensile strength, flexural strength, elastic modulus, and water absorption were carefully examined. The attained experimental results reveal that the mechanical and physical characteristics of concrete degrade with increasing the volume fraction of RFA replacing NFA. Also, increasing the weight percentage of nano-silica replacing cement up to 6% in conventional concrete and that containing RFA improves the mechanical and physical properties, the optimum percentage of which was determined as 4.5%. Furthermore, relationships were recommended for predicting the compressive, splitting tensile, and flexural strengths as well as the elastic modulus of concrete mixes by including the RFA and nano-silica replacement levels, which are in acceptable accordance with the experiments in the present study and those available in the technical literature. Finally, to investigate the environmental effects of recycled concrete with different RFA substitution levels and colloidal nano-silica incorporation, the problem-based CML 2000 and the damage-based IMPACT2002 + methods were applied using SimaPro9 software. Thus, environmental parameters such as acidification, global warming potential (GWP), eutrophication, natural resources, ecosystem quality, and human health were inspected. Subsequently, the GWP results were compared and presented using the CML 2000 and the Intergovernmental Panel on Climate Change (IPCC) approaches. To verify the estimates, all the attained results were examined against those captured from the Building for Environmental and Economic Sustainability (BEES) method. Findings show that despite the implementation of different unit measurements in different methods, the environmental effects in the CML 2000 and BEES meth-odologies are almost the same, suggesting that nano-silica is a raw material with the greatest environmental impact. Additionally, based on the life cycle comparison results of manufacturing one cubic meter of concrete with different mix designs using the damage evaluation approach, IMPACT 2002+, concrete with the RF0NS6 mix design triggered the highest damage extent in natural resource, climate change, ecosystem, and human health categories, respectively. This study fills a significant research gap from an environmental perspective by comprehensively investigating the durability and mechanical specifications of concrete containing RFA and nano-silica pozzolan. The findings presented in this research provide valuable insights into the realm of sustainable construction practices, paving the way for novel advancements in concrete technology.
... Also, according to the test results, the splitting tensile capacity of the samples declined by 19% at the RFA replacement percentage of 70%. Moreover, Nam, et al. [8] stated that the compressive and tensile capacities of RFAC were 10 and 26% less than concrete containing natural fine aggregate (NFA), respectively. Akono, et al. [9] studied the microstructure of concrete with RFA and reported that the porosity of C-S-H gel in RFA concrete was 56% of the total porosity. ...
n this study, the effect of colloidal nano-silica replacing a fraction of cement and recycled concrete fine aggregate replacingnatural sand on the post-fire mechanical features and durability of concrete was explored. To achieve this goal, 189 concretesamples were manufactured in total, with key variables being the volume of fine aggregate at 0, 50, and 100% replacingnatural fine aggregate, the volume of nano-silica at 1.5, 3, 4.5, and 6% replacing the cement weight, and the exposure tem-perature at 20, 300, and 600 °C. Parameters selected for consideration in the concretes consisted of compressive capacity,splitting tensile capacity, elastic modulus, ultrasonic pulse velocity (UPV), and weight loss. Furthermore, using scanningelectron microscopy (SEM) imaging, the microstructural condition of different sample groups was investigated. According tothe findings, as the content of the recycled fine aggregate (RFA) replacing natural fine aggregate increased, the compressivecapacity of the unheated and heated concretes declined, and the rate of this drop became greater as the replacement volumeincreased. On the other hand, the presence of the nano-silica and an increase in its content replacing the cement content inrecycled aggregate concrete improved the compressive strength relative to the reference concrete for all the exposure tem-peratures, with the greatest improvement for the replacement percentage of 4.5%. In addition, the heat-induced compressivecapacity drop was more pronounced at higher replacement levels of nano-silica. With a rise in the exposure temperature ofthe samples with only the recycled fine aggregate, fewer microcracks formed compared with the samples containing bothrecycled fine aggregate and nano-silica. The maximum weight loss occurred in the recycled sample containing the highestcontents of nano-silica and recycled aggregate. Afterward, it was attempted to estimate the mechanical features of concrete bydeveloping several empirical formulas as a function of temperature and volume fractions of recycled fine aggregate and nano-silica. These formulas were evaluated against the test data of this study and others, which showed an acceptable correlation.Finally, the findings of the tests were evaluated against the predictions of ACI 216, EN 1994–1-2, EN 1992–1-2, and ASCE.
... Addition of metallic and nonmetallic fibers in mono and hybrid form improved the bond stress-slip response of concrete (Ganesan et al. 2014;Hameed et al. 2013). Addition of fibers in recycled aggregate concrete helps to offset the reduction in mechanical properties of concrete caused by incorporation of recycled aggregates (Nam et al. 2016;Sryh and Forth 2015). ...
This paper presents an experimental investigation of bond stress-slip behavior of steel bars embedded in mono and hybrid fiber-reinforced recycled aggregate concrete. The main study parameters investigated were type of fibers and their dosage in terms of volumetric fraction. Crimped steel fibers and polypropylene fibers were used in mono and hybrid forms at two different volume fractions of 0.25 and 0.50%. Beam and cylinder specimens were cast and tested to investigate the bond stress-slip behavior and compressive strength of concrete, respectively. Experimental results depicted that partial replacement of natural aggregates with recycled aggregates showed negative impact on maximum bond strength of concrete. However, overall bond stress-slip behavior was similar for both natural aggregate concrete and recycled aggregate concrete. Addition of crimped steel fibers at 0.5% in mono form and polypropylene and steel fibers at 0.25% each in hybrid form showed significant improvement in bond strength and bond toughness of steel bars embedded in recycled aggregate concrete.
... Several proposed factors influence the bleeding and plastic shrinkage cracking of concrete. A concise review of literature shows that a considerable number of studies investigated the effects of varying cement properties [23][24][25], addition of fibres [26][27][28][29], and inclusion of shrinkage reducing admixtures [30,31] on concrete bleeding and plastic induced cracking. However, another important factor is the presence of MFA in MS, which has not appeared in any published literature to date. ...
Construction industries have started to utilize manufactured sand (MS) as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain MS, which also produces a considerable amount of microfine aggregate (MFA). The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying MFA levels, specifically 0%, 3%, 6%, 9%, and 12% (by weight) as the partial replacements of MS on bleeding and plastic shrinkage cracking of concrete. In addition to the varying MFA levels, some concrete mixes also included fly ash (FA) and superplasticizer to investigate the effect of free-water content in the mixes. The bleeding test data were taken as on-site measurements, while the cracks from the plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life gradually decreased, while a progressive increase was observed for crack width, crack length, and crack area.
... PVA fiber has been proved to restrain the free deformation of cementitious composite s [39,40]. Nevertheless, total shrinkage of PVA-ECC may reach triple that of ordinary concrete when identical water to cement ratio (w/c) is adopted [41]. ...
Engineered cementitious composite (ECC) enjoys huge potential in building structures thanks to its excellent tensile performance and energy absorption ability. However, free deformation of ECC deserves better understanding since large shrinkage strain usually induces internal tensile stress which would lead to cracking under constraint. Present study focuses on the full life-cycle shrinkage of polyvinyl alcohol (PVA) fiber reinforced ECC. Shrinkage and relative humidity (RH) at three water to cement (w/c) ratios were experimentally tested through novel integrated deformation measurement device. In contrast, plain mortars with the same w/c ratios were compared to evaluate the impact of PVA fiber on the over-time deformation and RH characteristics. Thereafter, shrinkage model considering fiber influence coefficient is established to simulate autogenous and drying shrinkage of PVA-ECC. Results show that full life-cycle shrinkage can be divided into two stages according to the internal RH measured. Distinct restraint effect of PVA fiber on both stages are observed. By comparing experimental and simulation results of PVA-ECC, the proposed fiber influence coefficient-based shrinkage model well illustrates the effect of PVA fiber, especially for high strength cementitious composites with relatively low w/c.
... The principal phenomenon for the cracking is the creation of negative tensile pressure at the surface, which pulls the particles and propagates the hairline cracks at the surface. [17][18][19] From the concise review of literature, effects of varying cement properties, [20][21][22] addition of fibers [23][24][25][26] and inclusion of shrinkage reducing admixtures 27,28 were proposed as the factors for bleeding and plastic shrinkage induced cracking of concrete. The presence of MFA could be also considered as a key factor, which is not appeared in any literature. ...
Manufactured sand (MS) has been started utilizing as an alternative in constructions due to the escalated demand for river sand (RS). The microfine aggregate (MFA) is a salient constituent in manufactured sand, which is a crushed reactive form of parent rocks having particles less than 0.075 mm. This paper presents the effects of varying microfine aggregate levels on bleeding , plastic shrinkage cracking (PSC) and compressive strength of MS made concrete. Two types of MS were utilized: MS from Hornblende-Gneiss rock (MH) and MS from Charnockite rock (MC) and the MFA level was ranged from 0% to 12% at 3% increments and the reference concrete was prepared with RS alone. With the MFA levels, the bleeding of MS concretes was reduced where, at 0% MFA level the maximum bleeding rates were observed for MC (1.63 kg/m 2) and MH (0.84 kg/m 2) concretes. PSC results were analyzed from an image processing technique, which revealed an increasing trend of mean and maximum crack widths, crack length and crack area with the MFA levels. At 0% MFA, the mean crack width of MC (0.19 mm) and MH (0.17 mm) con-cretes manifested marginally similar to RS concrete (0.17 mm). The decreasing bleeding with the MFA levels can be attributed to the increasing severity to PSC. Moreover, the optimum 28 days compressive strength of MC (57.5 MPa) and MH (56.1 MPa) concretes was achieved at 3% MFA level which are higher than RS concrete (51.5 MPa). Consequently, the MFA level should be limited to 3% for better plastic and hardened performance of MS made concrete.
... Nowadays, many materials incorporate fibers in their matrix in order to enhance their mechanical properties and to control crack propagation [31]. The cracking potential [24], and Nam et al. [28] High strength concrete 4 Saradar et al. [29], Dopko et al. [23], Shen et al. [20], and Shen et al. [21] Self-consolidating concrete 3 Abdelrazik and Khayat [22], Kassimi and Khayat [24], and Khayat, Kassimi, and Ghoddousi [25] Ultra High-performance concrete 3 Yoo et al. [14], Yoo et al. [15], and Yoo, Banthia e Yoon [16] Super workable concrete 2 Abdelrazik and Khayat [22] and Kassimi and Khayat [24] Lightweight concrete 1 Daneti, Wee and Thangayah [27] High-performance concrete 1 Shen et al. [19] High strength self-consolidating concrete 1 Li et al. [17] Not mentioned 1 Rong et al. [18] depends directly on fiber characteristics, such as volume incorporated, length, diameter, aspect ratio, and others [24]. Fibers can be classified into macro and microfibers. ...
... Through the SMS, it was found out that steel and polypropylene have been the main microfibers studied. The volume of fibers, by volume of concrete, is also indicated in Table 3 [26], and Ehrenbring et al. [5] High-elastic-modulus carbon 0.1-0.5% Dopko et al. [23] PVA 0.06-0.5% Nam et al. [28], Ehrenbring et al. [5], and Li et al. [17] Nylon 0.05-0.10% Nam et al. [28] Recycled polyester 0.5% Ehrenbring et al. [5] Glass Glass [not specified] 0.1-0.5% Daneti, Wee and Thangayah [27], and Saradar et al. [29] Natural -organic Sisal 0.25-0.5% Borges, Motta and Pinto [26] Rami 0.25-0.5% Borges, Motta and Pinto [26] Natural -inorganic Basalt 0.1% Saradar et al. [29] Yousefieh et al. [4] studied the addition of polypropylene microfibers (diameter and length of 0.022 and 12 mm, respectively) to the concrete at a dosage of 0.2% by concrete volume. ...
... The volume of fibers, by volume of concrete, is also indicated in Table 3 [26], and Ehrenbring et al. [5] High-elastic-modulus carbon 0.1-0.5% Dopko et al. [23] PVA 0.06-0.5% Nam et al. [28], Ehrenbring et al. [5], and Li et al. [17] Nylon 0.05-0.10% Nam et al. [28] Recycled polyester 0.5% Ehrenbring et al. [5] Glass Glass [not specified] 0.1-0.5% Daneti, Wee and Thangayah [27], and Saradar et al. [29] Natural -organic Sisal 0.25-0.5% Borges, Motta and Pinto [26] Rami 0.25-0.5% Borges, Motta and Pinto [26] Natural -inorganic Basalt 0.1% Saradar et al. [29] Yousefieh et al. [4] studied the addition of polypropylene microfibers (diameter and length of 0.022 and 12 mm, respectively) to the concrete at a dosage of 0.2% by concrete volume. As a result, during the restrained ring test, fiber reinforced concrete and conventional concrete obtained a cracking time of 66 h and 48 h, with a maximum strain of 30.02 µm/m and 22.44 µm/ m, respectively. ...
Nowadays, a significant interest in improving the durability of concrete structures has been growing due to the high cost of rehabilitation. Some pathologies, such as cracks, might affect the appearance and/or indicate a lack of durability. Many causes contribute to the development of cracks in concrete, like shrinkage. To overcome those deficiencies, the addition of fibers within the cement matrix has been pointed out as an effective method to control crack propagation because of the bridging effect. To assess the drying shrinkage of cementitious material, a restrained ring test has been proposed and investigated in the literature. In that context, a systematic mapping study (SMS) was carried out to determine the main developments regarding the application of microfiber reinforced concrete as a strategy to mitigate shrinkage at early ages. The goal of this SMS was to determine which microfibers have been presented by the literature to control drying shrinkage under a restrained ring test, as well as their dosage and susceptibility to cracking. The search was carried out in the Scopus database, within the years 2011–2021. A total of 21 articles were full-text reviewed. The study of drying shrinkage has increased in the last years. In addition, synthetic and metallic microfibers, with an emphasis on polypropylene and steel, are the most covered microfibers in the literature. In conclusion, microfibers are efficient in controlling crack due to drying shrinkage, resulting in a reduction in the crack opening, postponing the age of the crack, and providing greater strains than plain concrete.
