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Behzad Nematollahi - One of the best experts on this subject based on the ideXlab platform.
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sustainable fiber reinforced strain hardening Composites using Geopolymer as complete replacement of portland cement
International Conference on Strain-Hardening Cement-Based Composites, 2017Co-Authors: Behzad Nematollahi, Jay G SanjayanAbstract:Strain-hardening cementitious Composite (SHCC) is a special class of high-performance fiber-reinforced cementitious Composites which exhibits strain-hardening behavior with very high tensile ductility of up to 5% at a moderate fiber content (2% or less by volume). Typically high cement content is used in this Composite resulting in high autogenous shrinkage, heat of hydration, and cost. In addition, the associated increase in the CO2 emissions and embodied energy arising from the production of ordinary Portland cement (OPC) can compromise sustainability credentials of SHCCs. In the recent years the authors of this study developed an OPC-less strain-hardening Geopolymer Composite (SHGC). Geopolymer is used as ‘complete’ replacement of OPC in SHGC composition. Geopolymer is a sustainable alternative to OPC which emits at least 80% less CO2 and requires about 60% less energy as compared to production of OPC. The developed SHGCs are promising sustainable alternatives to typical SHCC, expecting to promote sustainability of the infrastructures via concurrent improvements of material greenness and infrastructure durability through very high tensile ductility and tight crack width control. This paper presents an overview of the authors’ research work on development and investigation of properties of SHGCs. The paper also presents a quantitative comparison of material sustainability performance of the developed SHGCs with typical SHCC.
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High ductile behavior of a polyethylene fiber-reinforced one-part Geopolymer Composite: A micromechanics-based investigation
Archives of Civil and Mechanical Engineering, 2017Co-Authors: Behzad Nematollahi, Jay Sanjayan, Enhua YangAbstract:This study investigates the tensile performance a one-part strain hardening Geopolymer Composite (SHGC) reinforced by ultra-high-molecular-weight polyethylene (PE) fibers. The developed Composite as a “dry mix” uses a small amount of solid activator rather than large quantities of commonly used alkaline solutions and eliminates the necessity for heat curing. The quantitative influences of curing condition (heat and ambient temperature curing) and type of fiber (poly vinyl alcohol (PVA) and PE fibers) on the macroscale properties of the matrix and Composite including workability, density, compressive strength, and uniaxial tensile performance were evaluated. A micromechanics-based investigation was performed to explain the experimentally observed macroscopic high tensile ductility of the developed one-part PE-SHGCs. The investigation involved determination of the matrix fracture properties and the fiber-matrix interface properties using fracture toughness tests and single-fiber pullout tests, respectively. The fiber-bridging constitutive law of the Composites was computed via a micromechanics-based model to link the material microstructures to macroscopic Composite tensile performance. The results indicated that the ambient temperature curing increased the compressive and tensile strengths, but reduced the tensile ductility of the one-part PE-SHGCs. The one-part PE-SHGCs exhibited lower compressive and tensile strengths, but higher tensile ductility compared to the one-part PVA-SHGC.
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micromechanics constitutive modelling and optimization of strain hardening Geopolymer Composite
Ceramics International, 2017Co-Authors: Behzad Nematollahi, Enhua Yang, Jishen Qiu, Jay SanjayanAbstract:Abstract This paper investigates the micromechanics constitutive modelling and optimization of a fiber-reinforced strain-hardening Geopolymer Composite (SHGC) recently developed by the authors. Micromechanical parameters of the developed fly ash-based SHGC were independently measured or deduced to compute the analytical crack bridging (σ-δ) relation of the Composite. The predicted σ-δ relation was compared with the experimental test results. It was confirmed that the previously developed micromechanics-based model can reasonably predict the σ-δ relation of fly ash-based SHGCs. Using the verified model, a parametric study was then performed to evaluate the effects of fiber length, fiber surface oil-coating, and matrix fracture toughness on critical (minimum) fiber content required to exhibit saturated pseudo strain-hardening (PSH) behavior. The results indicated that the critical fiber content in fly ash-based SHGCs is mainly governed by the energy-based criterion. It was demonstrated that the fiber surface oil coating, the increase of fiber length and the reduction of matrix fracture toughness are effective approaches to reduce the critical fiber content. Using the model, it was demonstrated that fly ash-based SHGCs can be systematically optimized by proper tailoring of the material constituents to achieve saturated PSH behavior with the lowest amount of fiber, and thereby the lowest cost.
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micromechanics based investigation of a sustainable ambient temperature cured one part strain hardening Geopolymer Composite
Construction and Building Materials, 2017Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Jishen Qiu, Enhua YangAbstract:Abstract Geopolymer Composite research is aimed to make sustainable alternatives to Portland cement-based Composites. However, the two main obstacles for commercialization are the use of large quantities of user-hostile liquid activators and heat curing. This study is aimed to overcome these obstacles by developing an ambient temperature cured “one-part” strain hardening Geopolymer Composite (SHGC). The developed Composite as a “dry mix” uses a small amount of solid activator and eliminates the necessity for heat curing. The quantitative influences of curing condition and type of slag on the Composite tensile performance were evaluated. The developed Composite demonstrated strong strain hardening behavior comparable to typical strain hardening cementitious Composite (SHCC) with high tensile strength of 4.6 MPa and very high tensile strain capacity of 4.2%. A micromechanics-based investigation was performed to explain the experimentally observed macroscopic high tensile ductility of the developed Composite. The investigation involved determination of the matrix fracture properties and the fiber-matrix interface properties using fracture toughness tests and single-fiber pullout tests, respectively. The crack-bridging relation of the developed Composite, computed via a micromechanics-based model, satisfied the necessary strength and energy-based conditions of steady-state flat crack propagation, which result in sequential development of multiple cracking. The material sustainability evaluation verified that the developed ambient temperature cured one-part SHGC is a promising sustainable alternative to typical SHCC offering 76% less carbon emissions and 36% less energy consumption. This research presents the rational basis for design of such cement-less Composites with both high tensile ductility and high material sustainability.
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Microscale investigation of fiber-matrix interface properties of strain-hardening Geopolymer Composite
Ceramics International, 2017Co-Authors: Behzad Nematollahi, Enhua Yang, Jishen Qiu, Jay G SanjayanAbstract:Abstract This study reports the microscale investigation of a short fiber-reinforced fly ash-based strain-hardening Geopolymer Composite (SHGC), which possesses high tensile strength (4.7 MPa) and very high tensile strain capacity (4.3%). The investigation involved determination of the quantitative influences of the type of activator, water to Geopolymer solids ratio and fiber surface oil coating on the microscale fiber-matrix interface properties using single-fiber pullout tests. The effects of the measured interface properties on the crack bridging σ(δ) relation of the Composites were investigated using a micromechanics-based model to explain the experimentally observed macroscopic tensile ductility of the Composites. The computed σ(δ) relation of fly ash-based SHGCs satisfied the necessary micromechanics-based conditions of steady-state flat crack propagation, which result in strain-hardening behavior. This research provides an in-depth understanding of fundamental fiber-matrix interaction properties and mechanisms, and their consequent effects on crack-bridging and tensile performance of the developed fly ash-based SHGCs. This understanding presents the rational basis for design of such cement-less Composites.
Faiz Uddin Ahmed Shaikh - One of the best experts on this subject based on the ideXlab platform.
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Behaviour of Carbon and Basalt Fibres Reinforced Fly Ash Geopolymer at Elevated Temperatures
International Journal of Concrete Structures and Materials, 2018Co-Authors: Faiz Uddin Ahmed Shaikh, Sharany HaqueAbstract:This paper presents the behaviour of potassium activators synthesized fly ash Geopolymer containing carbon and basalt fibre at ambient and elevated temperature. Six series of fly ash based Geopolymer were cast where carbon and basalt fibre were added as 0.5, 1 and 1.5% by weight of fly ash. One extra control series without any fibre was also cast. Each series of samples were tested at ambient temperature and also heated at 200, 400, 600 and 800 °C and thus a total of 35 series of samples were tested in this study. The result shows that the Geopolymer containing 1 wt% basalt and 1 wt% carbon fibre exhibited better compressive strength, lower volumetric shrinkage and mass loss than other fibre contents. Among two fibres Composites, the carbon fibre Geopolymer exhibited better performance than its basalt fibre counterpart regardless of temperature. The microstructure of carbon fibre reinforced Geopolymer Composite is more compact containing fewer pores/voids than its basalt based counterpart at elevated temperatures. The results also support the fact that carbon fibre is better than basalt fibre at elevated temperature and showed better bonding with Geopolymer at elevated temperature.
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Experimental evaluation of quasi-static and dynamic compressive properties of ambient-cured high-strength plain and fiber reinforced Geopolymer Composites
Construction and Building Materials, 2018Co-Authors: Musaad Zaheer Nazir Khan, Yifei Hao, Hong Hao, Faiz Uddin Ahmed ShaikhAbstract:Abstract Heat cured Geopolymer binders have been studied extensively to establish their mechanical behaviour under quasi-static loading conditions and it has been found that they are capable of achieving comparable and in some cases better properties than ordinary Portland cement (OPC). However, as a novel binding material, minimal research has been conducted to understand their dynamic material response. This paper presents the dynamic compressive properties of a newly synthesized high-strength ambient cured Geopolymer mortar and hybrid steel-polyethylene fiber reinforced Geopolymer Composite (FRGC). Dynamic compressive tests are carried out using the O100-mm split Hopkinson pressure bar (SHPB) apparatus with pulse shaping technique whereas a 160-ton hydraulic test machine is used for quasi-static compressive tests. The dynamic compressive properties of plain and FRGC including stress–strain curves, strength enhancement, impact toughness and energy absorption capability are obtained and compared with those observed under quasi-static actions. A high-speed camera is used to record the failure processes of samples under impact. The test results show that the dynamic compressive mechanical properties of plain and FRGC exhibit strong strain rate dependency. The DIFs (dynamic increase factors) of samples increase approximately linearly with the average strain rate in a logarithmic manner. Obvious binomial relationships are noticed between the energy absorption capacity and average strain rate of tested samples, such that the strain rate sensitivity threshold exists at 30 s−1 and 66 s−1 for plain and FRGC materials, respectively. Empirical DIF relations are proposed which can be used to model the developed Composite materials and structures subjected to static and impact loads.
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matrix design of strain hardening fiber reinforced engineered Geopolymer Composite
Composites Part B-engineering, 2016Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Faiz Uddin Ahmed ShaikhAbstract:Abstract The feasibility of developing a fiber reinforced engineered Geopolymer Composite (EGC) exhibiting strain hardening behavior under uni-axial tension has been recently demonstrated. The effect of different alkaline activators on the matrix and Composite behavior of such EGC has also been evaluated to enhance its compressive and tensile strengths with relatively low concentration activator combinations. The focus of this study, as a follow up investigation, is to evaluate the quantitative influence of Geopolymer matrix properties on the strain hardening behavior of the recently developed fly ash-based EGC with the aim of selecting the appropriate type of Geopolymer matrix to manufacture the strain hardening EGC with enhanced elastic modulus while maintaining the tensile ductility behavior of the Composite. The effects of water to Geopolymer solids ratio, sand size and sand content, as the most significant matrix-related parameters, on the matrix properties including workability, compressive strength, elastic modulus, fracture toughness and crack tip toughness, and the uni-axial tensile performance of the Composite were evaluated. Experimental results revealed that lowering the water to Geopolymer solids ratio and the addition of sand enhanced the elastic modulus of the Geopolymer matrix and Composite in all cases. However, the excessive use of fine sand and the use of coarse sand adversely affected the strain hardening behavior of the developed EGC due to the increase of the matrix fracture toughness and the first-crack strength of the Composite. Only Geopolymer matrices with suitable fracture toughness, as defined by the micromechanics design model, maintained the desirable tensile ductility of the developed fly ash-based EGC.
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tensile strain hardening behavior of pva fiber reinforced engineered Geopolymer Composite
Journal of Materials in Civil Engineering, 2015Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Faiz Uddin Ahmed ShaikhAbstract:AbstractThis paper is aimed to improve the mechanical properties (namely compressive and tensile strengths) of a recently developed fly ash-based engineered Geopolymer Composite (EGC) with relatively low-concentration activator combinations. In this regard, four different activator combinations (including two Na-based solutions and one K-based activator solution, and one lime-based activator combination in the form of powder) were used to develop the fly ash-based EGCs exhibiting strain hardening behavior under uniaxial tension. Randomly oriented short polyvinyl alcohol (PVA) fibers (2% v/v) were used to reinforce the relatively brittle low-calcium (Class F) fly ash-based Geopolymer matrix. The matrix and Composite properties of the developed fly ash-based EGCs [including workability of the fresh matrix, density, compressive strength, matrix fracture properties (comprising elastic modulus, fracture toughness, and Composite crack tip toughness), and uniaxial tensile behavior] were evaluated. A counterpart ...
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comparative deflection hardening behavior of short fiber reinforced Geopolymer Composites
Construction and Building Materials, 2014Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Faiz Uddin Ahmed ShaikhAbstract:This study evaluates the behavior of a recently developed ductile fiber reinforced Geopolymer Composite (DFRGC) exhibiting deflection hardening and multiple cracking behavior in flexure employing four different activator combinations including two Na-based and one K-based activator solutions, and one Ca-based activator combination in the form of powder. Randomly oriented short poly vinyl alcohol (PVA) fibers (2% v/v) were used to reinforce the relatively brittle low calcium (Class F) fly ash-based Geopolymer matrix. The matrix and Composite properties of the developed fly ash-based DFRGCs including workability of the fresh matrix, density, compressive strength, matrix fracture properties comprising elastic modulus, fracture toughness and Composite crack tip toughness, and flexural behavior were evaluated. A reference ductile fiber reinforced cementitious Composite (DFRCC) with water to cement ratio corresponding to the activator solution to fly ash ratio of the DFRGCs was also made for comparison. Experimental results revealed that all DFRGCs, regardless of their type of activator combinations, exhibited deflection hardening behavior accompanied by multiple fine cracks in bending. The DFRGC-Na-1 Composite exhibited superior deflection capacity, matrix fracture properties, compressive and flexural strengths with significantly enhanced Composite ductility and toughness.
Jay G Sanjayan - One of the best experts on this subject based on the ideXlab platform.
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sustainable fiber reinforced strain hardening Composites using Geopolymer as complete replacement of portland cement
International Conference on Strain-Hardening Cement-Based Composites, 2017Co-Authors: Behzad Nematollahi, Jay G SanjayanAbstract:Strain-hardening cementitious Composite (SHCC) is a special class of high-performance fiber-reinforced cementitious Composites which exhibits strain-hardening behavior with very high tensile ductility of up to 5% at a moderate fiber content (2% or less by volume). Typically high cement content is used in this Composite resulting in high autogenous shrinkage, heat of hydration, and cost. In addition, the associated increase in the CO2 emissions and embodied energy arising from the production of ordinary Portland cement (OPC) can compromise sustainability credentials of SHCCs. In the recent years the authors of this study developed an OPC-less strain-hardening Geopolymer Composite (SHGC). Geopolymer is used as ‘complete’ replacement of OPC in SHGC composition. Geopolymer is a sustainable alternative to OPC which emits at least 80% less CO2 and requires about 60% less energy as compared to production of OPC. The developed SHGCs are promising sustainable alternatives to typical SHCC, expecting to promote sustainability of the infrastructures via concurrent improvements of material greenness and infrastructure durability through very high tensile ductility and tight crack width control. This paper presents an overview of the authors’ research work on development and investigation of properties of SHGCs. The paper also presents a quantitative comparison of material sustainability performance of the developed SHGCs with typical SHCC.
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micromechanics based investigation of a sustainable ambient temperature cured one part strain hardening Geopolymer Composite
Construction and Building Materials, 2017Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Jishen Qiu, Enhua YangAbstract:Abstract Geopolymer Composite research is aimed to make sustainable alternatives to Portland cement-based Composites. However, the two main obstacles for commercialization are the use of large quantities of user-hostile liquid activators and heat curing. This study is aimed to overcome these obstacles by developing an ambient temperature cured “one-part” strain hardening Geopolymer Composite (SHGC). The developed Composite as a “dry mix” uses a small amount of solid activator and eliminates the necessity for heat curing. The quantitative influences of curing condition and type of slag on the Composite tensile performance were evaluated. The developed Composite demonstrated strong strain hardening behavior comparable to typical strain hardening cementitious Composite (SHCC) with high tensile strength of 4.6 MPa and very high tensile strain capacity of 4.2%. A micromechanics-based investigation was performed to explain the experimentally observed macroscopic high tensile ductility of the developed Composite. The investigation involved determination of the matrix fracture properties and the fiber-matrix interface properties using fracture toughness tests and single-fiber pullout tests, respectively. The crack-bridging relation of the developed Composite, computed via a micromechanics-based model, satisfied the necessary strength and energy-based conditions of steady-state flat crack propagation, which result in sequential development of multiple cracking. The material sustainability evaluation verified that the developed ambient temperature cured one-part SHGC is a promising sustainable alternative to typical SHCC offering 76% less carbon emissions and 36% less energy consumption. This research presents the rational basis for design of such cement-less Composites with both high tensile ductility and high material sustainability.
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Microscale investigation of fiber-matrix interface properties of strain-hardening Geopolymer Composite
Ceramics International, 2017Co-Authors: Behzad Nematollahi, Enhua Yang, Jishen Qiu, Jay G SanjayanAbstract:Abstract This study reports the microscale investigation of a short fiber-reinforced fly ash-based strain-hardening Geopolymer Composite (SHGC), which possesses high tensile strength (4.7 MPa) and very high tensile strain capacity (4.3%). The investigation involved determination of the quantitative influences of the type of activator, water to Geopolymer solids ratio and fiber surface oil coating on the microscale fiber-matrix interface properties using single-fiber pullout tests. The effects of the measured interface properties on the crack bridging σ(δ) relation of the Composites were investigated using a micromechanics-based model to explain the experimentally observed macroscopic tensile ductility of the Composites. The computed σ(δ) relation of fly ash-based SHGCs satisfied the necessary micromechanics-based conditions of steady-state flat crack propagation, which result in strain-hardening behavior. This research provides an in-depth understanding of fundamental fiber-matrix interaction properties and mechanisms, and their consequent effects on crack-bridging and tensile performance of the developed fly ash-based SHGCs. This understanding presents the rational basis for design of such cement-less Composites.
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matrix design of strain hardening fiber reinforced engineered Geopolymer Composite
Composites Part B-engineering, 2016Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Faiz Uddin Ahmed ShaikhAbstract:Abstract The feasibility of developing a fiber reinforced engineered Geopolymer Composite (EGC) exhibiting strain hardening behavior under uni-axial tension has been recently demonstrated. The effect of different alkaline activators on the matrix and Composite behavior of such EGC has also been evaluated to enhance its compressive and tensile strengths with relatively low concentration activator combinations. The focus of this study, as a follow up investigation, is to evaluate the quantitative influence of Geopolymer matrix properties on the strain hardening behavior of the recently developed fly ash-based EGC with the aim of selecting the appropriate type of Geopolymer matrix to manufacture the strain hardening EGC with enhanced elastic modulus while maintaining the tensile ductility behavior of the Composite. The effects of water to Geopolymer solids ratio, sand size and sand content, as the most significant matrix-related parameters, on the matrix properties including workability, compressive strength, elastic modulus, fracture toughness and crack tip toughness, and the uni-axial tensile performance of the Composite were evaluated. Experimental results revealed that lowering the water to Geopolymer solids ratio and the addition of sand enhanced the elastic modulus of the Geopolymer matrix and Composite in all cases. However, the excessive use of fine sand and the use of coarse sand adversely affected the strain hardening behavior of the developed EGC due to the increase of the matrix fracture toughness and the first-crack strength of the Composite. Only Geopolymer matrices with suitable fracture toughness, as defined by the micromechanics design model, maintained the desirable tensile ductility of the developed fly ash-based EGC.
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tensile strain hardening behavior of pva fiber reinforced engineered Geopolymer Composite
Journal of Materials in Civil Engineering, 2015Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Faiz Uddin Ahmed ShaikhAbstract:AbstractThis paper is aimed to improve the mechanical properties (namely compressive and tensile strengths) of a recently developed fly ash-based engineered Geopolymer Composite (EGC) with relatively low-concentration activator combinations. In this regard, four different activator combinations (including two Na-based solutions and one K-based activator solution, and one lime-based activator combination in the form of powder) were used to develop the fly ash-based EGCs exhibiting strain hardening behavior under uniaxial tension. Randomly oriented short polyvinyl alcohol (PVA) fibers (2% v/v) were used to reinforce the relatively brittle low-calcium (Class F) fly ash-based Geopolymer matrix. The matrix and Composite properties of the developed fly ash-based EGCs [including workability of the fresh matrix, density, compressive strength, matrix fracture properties (comprising elastic modulus, fracture toughness, and Composite crack tip toughness), and uniaxial tensile behavior] were evaluated. A counterpart ...
Shizhe Zhang - One of the best experts on this subject based on the ideXlab platform.
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micromechanics guided development of a slag fly ash based strain hardening Geopolymer Composite
Cement & Concrete Composites, 2020Co-Authors: Shizhe ZhangAbstract:Strain-hardening Geopolymer Composite (SHGC) lately emerged as a promising alternative to traditional strain-hardening cementitious Composite with added advantages of industrial by-product utilization and enhanced sustainability. However, as the design of SHGC requires multi-factor optimization, the application of traditional trial-and-error method is inefficient and hinders the development of this material. This paper aims at the development of a slag/fly ash-based SHGC with low slag content using a micromechanical model to guide the Composite mixture design. To this end, experimentally characterized physical properties of fiber, matrix and interface are used as input for the micromechanical model, which serves as a predictive tool for the tensile performance of SHGC. Following the guidance, a slag/fly ash-based SHGC with tensile strain capacity of 4.8% and ultimate tensile strength above 3.8 MPa was systematically developed. The feasibility and effectiveness of using micromechanics as the design basis of SHGC are demonstrated and experimentally verified.
Enhua Yang - One of the best experts on this subject based on the ideXlab platform.
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High ductile behavior of a polyethylene fiber-reinforced one-part Geopolymer Composite: A micromechanics-based investigation
Archives of Civil and Mechanical Engineering, 2017Co-Authors: Behzad Nematollahi, Jay Sanjayan, Enhua YangAbstract:This study investigates the tensile performance a one-part strain hardening Geopolymer Composite (SHGC) reinforced by ultra-high-molecular-weight polyethylene (PE) fibers. The developed Composite as a “dry mix” uses a small amount of solid activator rather than large quantities of commonly used alkaline solutions and eliminates the necessity for heat curing. The quantitative influences of curing condition (heat and ambient temperature curing) and type of fiber (poly vinyl alcohol (PVA) and PE fibers) on the macroscale properties of the matrix and Composite including workability, density, compressive strength, and uniaxial tensile performance were evaluated. A micromechanics-based investigation was performed to explain the experimentally observed macroscopic high tensile ductility of the developed one-part PE-SHGCs. The investigation involved determination of the matrix fracture properties and the fiber-matrix interface properties using fracture toughness tests and single-fiber pullout tests, respectively. The fiber-bridging constitutive law of the Composites was computed via a micromechanics-based model to link the material microstructures to macroscopic Composite tensile performance. The results indicated that the ambient temperature curing increased the compressive and tensile strengths, but reduced the tensile ductility of the one-part PE-SHGCs. The one-part PE-SHGCs exhibited lower compressive and tensile strengths, but higher tensile ductility compared to the one-part PVA-SHGC.
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micromechanics constitutive modelling and optimization of strain hardening Geopolymer Composite
Ceramics International, 2017Co-Authors: Behzad Nematollahi, Enhua Yang, Jishen Qiu, Jay SanjayanAbstract:Abstract This paper investigates the micromechanics constitutive modelling and optimization of a fiber-reinforced strain-hardening Geopolymer Composite (SHGC) recently developed by the authors. Micromechanical parameters of the developed fly ash-based SHGC were independently measured or deduced to compute the analytical crack bridging (σ-δ) relation of the Composite. The predicted σ-δ relation was compared with the experimental test results. It was confirmed that the previously developed micromechanics-based model can reasonably predict the σ-δ relation of fly ash-based SHGCs. Using the verified model, a parametric study was then performed to evaluate the effects of fiber length, fiber surface oil-coating, and matrix fracture toughness on critical (minimum) fiber content required to exhibit saturated pseudo strain-hardening (PSH) behavior. The results indicated that the critical fiber content in fly ash-based SHGCs is mainly governed by the energy-based criterion. It was demonstrated that the fiber surface oil coating, the increase of fiber length and the reduction of matrix fracture toughness are effective approaches to reduce the critical fiber content. Using the model, it was demonstrated that fly ash-based SHGCs can be systematically optimized by proper tailoring of the material constituents to achieve saturated PSH behavior with the lowest amount of fiber, and thereby the lowest cost.
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micromechanics based investigation of a sustainable ambient temperature cured one part strain hardening Geopolymer Composite
Construction and Building Materials, 2017Co-Authors: Behzad Nematollahi, Jay G Sanjayan, Jishen Qiu, Enhua YangAbstract:Abstract Geopolymer Composite research is aimed to make sustainable alternatives to Portland cement-based Composites. However, the two main obstacles for commercialization are the use of large quantities of user-hostile liquid activators and heat curing. This study is aimed to overcome these obstacles by developing an ambient temperature cured “one-part” strain hardening Geopolymer Composite (SHGC). The developed Composite as a “dry mix” uses a small amount of solid activator and eliminates the necessity for heat curing. The quantitative influences of curing condition and type of slag on the Composite tensile performance were evaluated. The developed Composite demonstrated strong strain hardening behavior comparable to typical strain hardening cementitious Composite (SHCC) with high tensile strength of 4.6 MPa and very high tensile strain capacity of 4.2%. A micromechanics-based investigation was performed to explain the experimentally observed macroscopic high tensile ductility of the developed Composite. The investigation involved determination of the matrix fracture properties and the fiber-matrix interface properties using fracture toughness tests and single-fiber pullout tests, respectively. The crack-bridging relation of the developed Composite, computed via a micromechanics-based model, satisfied the necessary strength and energy-based conditions of steady-state flat crack propagation, which result in sequential development of multiple cracking. The material sustainability evaluation verified that the developed ambient temperature cured one-part SHGC is a promising sustainable alternative to typical SHCC offering 76% less carbon emissions and 36% less energy consumption. This research presents the rational basis for design of such cement-less Composites with both high tensile ductility and high material sustainability.
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Microscale investigation of fiber-matrix interface properties of strain-hardening Geopolymer Composite
Ceramics International, 2017Co-Authors: Behzad Nematollahi, Enhua Yang, Jishen Qiu, Jay G SanjayanAbstract:Abstract This study reports the microscale investigation of a short fiber-reinforced fly ash-based strain-hardening Geopolymer Composite (SHGC), which possesses high tensile strength (4.7 MPa) and very high tensile strain capacity (4.3%). The investigation involved determination of the quantitative influences of the type of activator, water to Geopolymer solids ratio and fiber surface oil coating on the microscale fiber-matrix interface properties using single-fiber pullout tests. The effects of the measured interface properties on the crack bridging σ(δ) relation of the Composites were investigated using a micromechanics-based model to explain the experimentally observed macroscopic tensile ductility of the Composites. The computed σ(δ) relation of fly ash-based SHGCs satisfied the necessary micromechanics-based conditions of steady-state flat crack propagation, which result in strain-hardening behavior. This research provides an in-depth understanding of fundamental fiber-matrix interaction properties and mechanisms, and their consequent effects on crack-bridging and tensile performance of the developed fly ash-based SHGCs. This understanding presents the rational basis for design of such cement-less Composites.