Comparative Study on the Effects of Recycled Glass–Fiber ... · recycled glass fibers. Moreover,...
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Comparative Study on the Effects of Recycled Glass–Fiber on Drying Shrinkage Rate and Mechanical Properties of the Self-Compacting Mortar and Fly Ash–Slag Geopolymer Mortar Z. Abdollahnejad, Ph.D. 1 ; M. Mastali, Ph.D. 2 ; M. Mastali 3 ; and A. Dalvand, Ph.D. 4 Abstract: In this comprehensive experimental study, the effects of recycled glass fiber on the drying shrinkage and mechanical properties of the self-compacting mortar and fly ash–slag geopolymer mortar were investigated. An experimental/analytical approach was adopted to characterize the mechanical properties (compressive and flexural strength) and the drying shrinkage rate of the reinforced self-compacting mortars and fly ash–slag geopolymer mortars with inclusion of different recycled glass fiber volume fractions and lengths. To this end, a total of 207 specimens were experimentally tested. Scanning electron microscope (SEM) images were used to detect the failure mechanism of recycled glass fibers. Moreover, based on the collected data, some empirical equations were developed to correlate recycled glass fiber volume fractions to the mechanical properties of the reinforced fly ash–slag geopolymer mortars and self-compacting mortars, considering high values of coefficient of determination. The experimental results showed that adding recycled glass fiber has much greater effects on increasing the flexural strength and decreasing the drying shrinkage rate in fly ash–slag geopolymer mortars when compared to self-compacting mortars. DOI: 10.1061/(ASCE)MT.1943-5533.0001918. © 2017 American Society of Civil Engineers. Author keywords: Recycled glass fiber; Self-compacting mortar; Fly ash–slag geopolymer mortar; Mechanical properties; Drying shrinkage. Introduction Over the last three decades, sustainable cementitious materials have been rapidly developed, and the use of waste materials in cement- based composites has simultaneously achieved particular impor- tance. Using waste materials reduces negative environmental impacts and construction costs (Meddah et al. 2009). Therefore, various studies have been carried out to assess the feasibility of using the waste materials obtained from different sources in con- crete. In this way, many efforts have been made to improve the mechanical properties of concrete through using recycled fibers in reinforced concrete. In 2015, Khaloo et al. investigated the possibility of adding recycled polymer fibers in high performance concrete by character- izing the fresh and hardened properties of mixtures. Recycled fibers were from discarded car timing belts (Khaloo et al. 2015). The fiber lengths were 20 and 40 mm. Furthermore, different fiber volume fractions were used to reinforce the mix compositions, including 0.2, 0.5, 1, and 1.5% (Khaloo et al. 2015). Slump flow diameter was used to assess the fresh state properties of the reinforced concretes. The hardened properties of the reinforced concrete were characterized. The experimental results showed that using a low fiber volume fraction (up to 0.2%) increased the compressive strength, whereas adding higher fiber volume fractions reduced the compressive strength. Furthermore, the results indicated an im- provement in the flexural performance of the reinforced beams with the addition of up to 0.5% recycled fiber (Khaloo et al. 2015). Mastali et al. studied the effects of adding recycled glass fiber in self-compacting concrete (Mastali et al. 2016a). The specimens were reinforced by different fiber volume fractions, including 0.25, 0.75, and 1.25%. The average fiber length for all fiber volume frac- tions was 20 mm (Mastali et al. 2016a). The fresh state and hard- ened state properties of specimens were determined (Mastali et al. 2016a). The experimental results showed that addition of recycled fiber reduced the workability of mix compositions, whereas me- chanical properties and impact resistance of specimens enhanced with increasing fiber content (Mastali et al. 2016a). To the best of the authors’ knowledge, the effects of fiber length on drying shrinkage rate and mechanical properties of self- compacting mortar reinforced with recycled glass fibers have not been researched yet. Although some studies have reported the ef- fects of adding recycled glass and carbon fiber with an average fiber length of 20 mm on the impact resistance and mechanical proper- ties of self-compacting concrete (Mastali et al. 2016a, b), they have not included the effect of fiber lengths on mechanical properties. One of the most obvious defects of plain concrete is the forma- tion of microcracks caused by drying shrinkage because of high capillary pressure between wet and dry areas of the micropore network. The formation of these microcracks can significantly de- crease the mechanical and durability properties of concrete; there- fore, many studies have been conducted to decrease the drying 1 Researcher, Centre of Excellence in Engineered Fibre Composites, Faculty of Health, Engineering and Sciences, Univ. of Southern Queensland, West St., Darling Heights, QLD 4350, Australia. 2 Researcher, ISISE, Dept. of Civil Engineering, Minho Univ., Campus de Azurem, Carvalho St., 4800-058 Guimaraes, Portugal (corresponding author). E-mail: [email protected] 3 Graduate Student, Dept. of Civil Engineering, Western Michigan Univ., 1903 W Michigan Ave., Kalamazoo, MI 49008. 4 Assistant Professor, Dept. of Civil Engineering, School of Engineer- ing, Lorestan Univ., Tehran St., Khorramabad, 44316-68151 Lorestan, Iran. Note. This manuscript was submitted on August 16, 2016; approved on December 14, 2016; published online on April 7, 2017. Discussion period open until September 7, 2017; separate discussions must be submitted for individual papers. This paper is part of the Journal of Materials in Civil Engineering, © ASCE, ISSN 0899-1561. © ASCE 04017076-1 J. Mater. Civ. Eng. J. Mater. Civ. Eng., -1--1 Downloaded from ascelibrary.org by Western Michigan University on 04/07/17. Copyright ASCE. For personal use only; all rights reserved.
Transcript of Comparative Study on the Effects of Recycled Glass–Fiber ... · recycled glass fibers. Moreover,...
Comparative Study on the Effects of Recycled Glass–Fiberon Drying Shrinkage Rate and Mechanical Properties
of the Self-Compacting Mortar and Fly Ash–SlagGeopolymer Mortar
Z. Abdollahnejad, Ph.D.1; M. Mastali, Ph.D.2; M. Mastali3; and A. Dalvand, Ph.D.4
Abstract: In this comprehensive experimental study, the effects of recycled glass fiber on the drying shrinkage and mechanical properties ofthe self-compacting mortar and fly ash–slag geopolymer mortar were investigated. An experimental/analytical approach was adopted tocharacterize the mechanical properties (compressive and flexural strength) and the drying shrinkage rate of the reinforced self-compactingmortars and fly ash–slag geopolymer mortars with inclusion of different recycled glass fiber volume fractions and lengths. To this end, atotal of 207 specimens were experimentally tested. Scanning electron microscope (SEM) images were used to detect the failure mechanism ofrecycled glass fibers. Moreover, based on the collected data, some empirical equations were developed to correlate recycled glass fibervolume fractions to the mechanical properties of the reinforced fly ash–slag geopolymer mortars and self-compacting mortars, consideringhigh values of coefficient of determination. The experimental results showed that adding recycled glass fiber has much greater effectson increasing the flexural strength and decreasing the drying shrinkage rate in fly ash–slag geopolymer mortars when compared toself-compacting mortars. DOI: 10.1061/(ASCE)MT.1943-5533.0001918. © 2017 American Society of Civil Engineers.
Author keywords: Recycled glass fiber; Self-compacting mortar; Fly ash–slag geopolymer mortar; Mechanical properties; Dryingshrinkage.
Introduction
Over the last three decades, sustainable cementitious materials havebeen rapidly developed, and the use of waste materials in cement-based composites has simultaneously achieved particular impor-tance. Using waste materials reduces negative environmentalimpacts and construction costs (Meddah et al. 2009). Therefore,various studies have been carried out to assess the feasibility ofusing the waste materials obtained from different sources in con-crete. In this way, many efforts have been made to improve themechanical properties of concrete through using recycled fibersin reinforced concrete.
In 2015, Khaloo et al. investigated the possibility of addingrecycled polymer fibers in high performance concrete by character-izing the fresh and hardened properties of mixtures. Recycled fiberswere from discarded car timing belts (Khaloo et al. 2015). The fiberlengths were 20 and 40 mm. Furthermore, different fiber volumefractions were used to reinforce the mix compositions, including
0.2, 0.5, 1, and 1.5% (Khaloo et al. 2015). Slump flow diameterwas used to assess the fresh state properties of the reinforcedconcretes. The hardened properties of the reinforced concrete werecharacterized. The experimental results showed that using a lowfiber volume fraction (up to 0.2%) increased the compressivestrength, whereas adding higher fiber volume fractions reducedthe compressive strength. Furthermore, the results indicated an im-provement in the flexural performance of the reinforced beams withthe addition of up to 0.5% recycled fiber (Khaloo et al. 2015).
Mastali et al. studied the effects of adding recycled glass fiberin self-compacting concrete (Mastali et al. 2016a). The specimenswere reinforced by different fiber volume fractions, including 0.25,0.75, and 1.25%. The average fiber length for all fiber volume frac-tions was 20 mm (Mastali et al. 2016a). The fresh state and hard-ened state properties of specimens were determined (Mastali et al.2016a). The experimental results showed that addition of recycledfiber reduced the workability of mix compositions, whereas me-chanical properties and impact resistance of specimens enhancedwith increasing fiber content (Mastali et al. 2016a).
To the best of the authors’ knowledge, the effects of fiberlength on drying shrinkage rate and mechanical properties of self-compacting mortar reinforced with recycled glass fibers have notbeen researched yet. Although some studies have reported the ef-fects of adding recycled glass and carbon fiber with an average fiberlength of 20 mm on the impact resistance and mechanical proper-ties of self-compacting concrete (Mastali et al. 2016a, b), they havenot included the effect of fiber lengths on mechanical properties.
One of the most obvious defects of plain concrete is the forma-tion of microcracks caused by drying shrinkage because of highcapillary pressure between wet and dry areas of the microporenetwork. The formation of these microcracks can significantly de-crease the mechanical and durability properties of concrete; there-fore, many studies have been conducted to decrease the drying
1Researcher, Centre of Excellence in Engineered Fibre Composites,Faculty of Health, Engineering and Sciences, Univ. of Southern Queensland,West St., Darling Heights, QLD 4350, Australia.
2Researcher, ISISE, Dept. of Civil Engineering, Minho Univ., Campusde Azurem, Carvalho St., 4800-058 Guimaraes, Portugal (correspondingauthor). E-mail: [email protected]
3Graduate Student, Dept. of Civil Engineering, Western MichiganUniv., 1903 W Michigan Ave., Kalamazoo, MI 49008.
4Assistant Professor, Dept. of Civil Engineering, School of Engineer-ing, Lorestan Univ., Tehran St., Khorramabad, 44316-68151 Lorestan, Iran.
Note. This manuscript was submitted on August 16, 2016; approved onDecember 14, 2016; published online on April 7, 2017. Discussion periodopen until September 7, 2017; separate discussions must be submitted forindividual papers. This paper is part of the Journal of Materials in CivilEngineering, © ASCE, ISSN 0899-1561.
© ASCE 04017076-1 J. Mater. Civ. Eng.
J. Mater. Civ. Eng., -1--1
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