ORCID Profile
0000-0001-5069-2963
Current Organisations
Flinders University
,
University of Melbourne
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Publisher: Wiley
Date: 28-05-2020
Publisher: Springer Science and Business Media LLC
Date: 16-09-2019
Publisher: American Chemical Society (ACS)
Date: 04-12-2017
Abstract: Graphene materials have been extensively explored and successfully used to improve performances of cement composites. These formulations were mainly optimized based on different dosages of graphene additives, but with lack of understanding of how other parameters such as surface chemistry, size, charge, and defects of graphene structures could impact the physiochemical and mechanical properties of the final material. This paper presents the first experimental study to evaluate the influence of oxygen functional groups of graphene and defectiveness of graphene structures on the axial tension and compression properties of graphene-cement mortar composites. A series of reduced graphene oxide (rGO) s les with different levels of oxygen groups (high, mild, and low) were prepared by the reduction of graphene oxide (GO) using different concentrations of hydrazine (wt %, 0.1, 0.15, 0.2, 0.3, and 0.4%) and different reduction times (5, 10, 15, 30, and 60 min) and were added to cement mortar composites at an optimal dosage of 0.1%. A series of characterization methods including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy were performed to determine the distribution and mixing of the prepared rGO in the cement matrix and were correlated with the observed mechanical properties of rGO-cement mortar composites. The measurement of the axial tension and compression properties revealed that the oxygen level of rGO additives has a significant influence on the mechanical properties of cement composites. An addition of 0.1% rGO prepared by 15 min reduction and 0.2% (wt %) hydrazine with mild level of oxygen groups resulted in a maximum enhancement of 45.0 and 83.7%, respectively, in the 28-day tensile and compressive strengths in comparison with the plain cement mortar and were higher compared to the composite prepared with GO (37.5 and 77.7%, respectively). These results indicate that there is a strong influence of the level of oxygen groups and crystallinity of graphene structures on the physiochemical and mechanical properties. The influence of these two parameters are interconnected and their careful balancing is required to provide an optimum level of oxygen groups on rGO sheets to ensure that there is sufficient bonding between the calcium silicate hydrate (C-S-H) components in the cement matrix and minimum level of defects and higher crystallinity of graphene structures, which will improve the mechanical properties of the composite. Finding the optimized balance between these two parameters is required to formulate graphene cement composites with the highest performance.
Publisher: Elsevier BV
Date: 08-2022
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2018
Publisher: Trans Tech Publications, Ltd.
Date: 02-2017
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.729.122
Abstract: This study presents the results of the experimental study on the axial compressive behavior of the rubberized concrete under active confinement. Two different mixes of concretes with rubber replacement ratios of 0%, as a control mix, and 18% were prepared. The effects of the incorporation of rubber and the confining pressure on the compressive behavior of concrete were examined through tests of unconfined and actively confined concrete cylinders. The active confinement was applied by a Hoek cell at different pressures, including 5, 7.5, 10, 15, 20, and 25 MPa. The results indicate that the rubberized concrete exhibits lower compressive strength but higher axial and lateral deformation capacities than those of the conventional concrete.
Publisher: MDPI AG
Date: 22-02-2021
DOI: 10.3390/APP11041917
Abstract: Increasing the thermal insulation of building components to reduce the thermal energy loss of buildings has received significant attention. Owing to its porous structure, using expanded vermiculite as an alternative to natural river sand in the development of building materials would result in improvement of the thermal performance of buildings. This study investigates the properties of fly ash (FA)-based geopolymer mortars prepared with expanded vermiculite. The main aim of this study was to produce geopolymer mortar with lower thermal conductivity than conventional mortar for thermal insulation applications in buildings. A total of twelve batches of geopolymers were prepared for evaluating their different properties. The obtained results show that, at a given FA and expanded vermiculite content, the geopolymers prepared with a 10 molar NaOH solution exhibited a higher flowability, water absorption and porosity, as well as a lower dry unit weight, compressive strength, ultrasound pulse velocity and thermal conductivity compared with those prepared with a 15 molar NaOH solution. As is also shown, the geopolymers containing expanded vermiculite (15%) developed a lower flowability (~6%), dry unit weight (~6%), compressive strength (~7%), ultrasound pulse velocity (~6%) and thermal conductivity (~18%), as well as a higher apparent porosity (~6%) and water absorption (~9%) compared with those without expanded vermiculite at a given FA content and NaOH concentration. The findings of this study suggest that incorporating expanded vermiculite in FA-based geopolymer mortar can provide eco-friendly and lightweight building composites with improved sound and thermal insulation properties, contributing toward the reduction of the environmental effects of waste materials and conservation of natural sand.
Publisher: Elsevier BV
Date: 03-2017
Publisher: Elsevier BV
Date: 09-2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 02-2018
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 08-0311
Publisher: Elsevier BV
Date: 04-2021
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 12-2021
Publisher: ASME International
Date: 30-01-2013
DOI: 10.1115/1.4007682
Abstract: A new time integration scheme is presented for solving the differential equation of motion with nonlinear stiffness. In this new implicit method, it is assumed that the acceleration varies quadratically within each time step. By increasing the order of acceleration, more terms of the Taylor series are used, which are expected to have responses with better accuracy than the classical methods. By considering this assumption and employing two parameters δ and α, a new family of unconditionally stable schemes is obtained. The order of accuracy, numerical dissipation, and numerical dispersion are used to measure the accuracy of the proposed method. Second order accuracy is achieved for all values of δ and α. The proposed method presents less dissipation at the lower modes in comparison with Newmark's average acceleration, Wilson-θ, and generalized-α methods. Moreover, this second order accurate method can control numerical d ing in the higher modes. The numerical dispersion of the proposed method is compared with three unconditionally stable methods, namely, Newmark's average acceleration, Wilson-θ, and generalized-α methods. Furthermore, the overshooting effect of the proposed method is compared with these methods. By evaluating the computational time for analysis with similar time step duration, the proposed method is shown to be faster in comparison with the other methods.
Publisher: Elsevier BV
Date: 12-2023
Publisher: Inderscience Publishers
Date: 2020
Publisher: MDPI AG
Date: 27-02-2023
DOI: 10.3390/APP13053038
Abstract: The accurate prediction of reference points on the axial stress–axial strain relationship of fiber-reinforced polymer (FRP)-confined concrete is vital to pre-design structures made with this system. This study uses an artificial neural network (ANN) for predicting hoop rupture strain (εh,rup) and transition zone, namely transition strain (εc1) and stress (f’c1), on axial stress–strain curves of FRP-confined concrete. These are key parameters for estimating a transition zone of stress–strain curves. In this study, accompanied with these parameters, ultimate condition parameters, including compressive strength and ultimate axial strain, were predicted using a comprehensive database. Various combinations of input data and ANN parameters were used to increase the accuracy of the predictions. A sensitivity analysis and a model validation assessment were performed to evaluate the predictability of the developed models. At the end, a comparison between the proposed models in this study and existing ANN and design-oriented models was presented. It is shown that the accuracy of the developed ANN models in this study is higher or comparable to that of existing ANN models. Additionally, the developed models in this study to predict f’c1 and εc1 exhibit a higher accuracy compared to existing design-oriented models. These results indicate that the proposed ANN models capture the lateral confinement effect on ultimate and transition zones of FRP-confined concrete with a more robust performance compared to existing models.
Publisher: Elsevier BV
Date: 11-2201
Publisher: Thomas Telford Ltd.
Date: 05-2020
Abstract: The aim of this study was to develop sustainable concrete using waste products to reduce both the carbon dioxide emissions associated with concrete production and the extraction of non-renewable natural resources. The development of the new sustainable concrete involved the replacement of cement with industrial by-products (fly ash, glass powder and ground granulated blast-furnace slag (GGBS)) and the replacement of natural river sand (NS) with waste-based sand (lead-smelter slag (LSS)). Twenty-four batches of mortar mixes were produced and tests were performed to determine the flowability, compressive strength and direct tensile strength of each batch. Microstructural analysis was undertaken to explain the experimentally obtained properties of the mortars. The compressive and tensile strengths of waste-based mortars containing LSS were found to be similar to those of mortars containing NS. Mortars with 80% replacement of cement with GGBS and 100% replacement of NS with LSS showed minimal strength reduction (4%) compared with the conventional mortar. The strength reductions of the waste-based mortars compared with the conventional mortar increased at 90% and 100% cement replacement levels, but remained limited to approximately 20% (at 90% GGBS) and 30% (at 100% GGBS). The findings of this study are promising and point to the potential development of new structural-grade mortars using full or near-full replacement of cement with industrial by-products and full replacement of NS with waste-based sand.
Publisher: Wiley
Date: 26-05-2021
Abstract: The focus of this study is to investigate the effect of using coarse recycled concrete aggregates (RCAs) as an alternative material to natural coarse aggregate on the fresh, mechanical and durability behavior of concrete reinforced with steel fiber. Eighteen unique concrete mixes with RCA content of 0%, 50%, and 100% and steel fiber content of 0%, 1%, and 2% were prepared, and tests were performed to study slump, density, compressive and splitting tensile strengths, flexural behavior, surface hardness, surface abrasion resistance, water absorption, and sorptivity of each mix. It is shown that concrete containing RCA has a lower unit weight, compressive, splitting tensile and flexural strength, flexural toughness, surface hardness, and abrasion resistance, and a higher water absorption and sorptivity in comparison with conventional concrete. An increased compressive, splitting tensile and flexural strength, flexural toughness, surface hardness, and abrasion resistance, and a decreased water absorption and sorptivity of concrete with an increased steel fiber content from 1% to 2% is less significant compared to those from 0% to 1%. The results also show that, at RCA content of 50%, incorporating 1% steel fiber develops a concrete mix with similar or even better properties compared to unreinforced conventional concrete. At 100% RCA content, incorporating 2% steel fiber develops a concrete mix with similar properties to unreinforced conventional concrete having water to cement ratio of 0.3, but inferior properties to unreinforced conventional concrete having water to cement ratio of 0.5. These findings indicate that recycled aggregate concrete with similar or even better properties compared to concrete with natural aggregate can be developed through properly designing mixes, providing a great avenue toward the production of green construction material for structural applications.
Publisher: Elsevier BV
Date: 02-2017
Publisher: Elsevier BV
Date: 07-2019
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 05-2022
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 05-1976
Publisher: Springer Singapore
Date: 04-09-2019
Publisher: Elsevier BV
Date: 02-2021
Publisher: Informa UK Limited
Date: 04-12-2013
Publisher: Elsevier BV
Date: 05-2021
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 12-2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 02-2012
Publisher: IEEE
Date: 2010
Publisher: Springer Science and Business Media LLC
Date: 08-2018
Publisher: Elsevier BV
Date: 02-2018
Publisher: IEEE
Date: 2010
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 02-2014
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 12-2019
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2019
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2015
Publisher: Elsevier BV
Date: 03-2020
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2016
Publisher: Springer Singapore
Date: 04-09-2019
Publisher: Elsevier BV
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 13-09-2016
Publisher: World Scientific Pub Co Pte Lt
Date: 02-2016
DOI: 10.1142/S0219876216500055
Abstract: This paper presents a weighted residual method with several weight functions for solving differential equation of motion in nonlinear structural dynamics problems. Order of variation of acceleration is assumed to be quadratic in each time step in which polynomial of displacement would contain five unknown coefficients. Five equations are required for determination of these coefficients in each time step. These equations are obtained from initial conditions, satisfying equation of motions at both ends, and weighted residual integration. In this study, four procedures are considered for weight function to be used in the weighted residual integration as unit weight function, Petrov–Galerkin’s weight function, least square weight function, and collocation weight function. Due to higher order of acceleration in the proposed method, the results indicate better and more accurate responses. Among the tested functions, the unit weighted function method demonstrated to be non-dissipative and its numerical dispersion showed to be clearly less than the common Newmark’s linear acceleration method. Also critical time step duration in stability investigation for weighted function procedure showed to be larger than the critical time step duration obtained by other methods used in the nonlinear structural dynamics problems.
Publisher: Springer Science and Business Media LLC
Date: 25-07-2016
Publisher: Elsevier
Date: 2020
Publisher: IOP Publishing
Date: 2018
Publisher: Elsevier BV
Date: 10-2019
Publisher: IOP Publishing
Date: 08-2017
Publisher: IOP Publishing
Date: 2018
Publisher: Elsevier BV
Date: 06-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7RA10066C
Abstract: This paper presents a comprehensive study to evaluate the influence of graphene oxide (GO) concentration on the physiochemical and mechanical properties of cement mortar composites.
Publisher: Elsevier BV
Date: 02-2022
Publisher: Trans Tech Publications, Ltd.
Date: 2017
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.1142.349
Abstract: This study presents an extended finite element (FE) model based on concrete damage-plasticity approach for fiber-reinforced polymer (FRP)-confined normal-strength and high-strength concrete (NSC and HSC). The proposed model is based on Lubliner’s model and it accurately incorporates the effects of confinement level, concrete strength, and nonlinear dilation behavior. Failure surface and flow rule were established using an up-to-date database. In order to validate the extended damage-plasticity model, finite element (FE) model is developed for specimens under a wide range of confining pressures. The results indicate that the model predictions of FRP-confined NSC and HSC are in good agreement with the experimental results.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Trans Tech Publications, Ltd.
Date: 06-2017
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.737.511
Abstract: This study presents the analysis of the constitutive behavior of fiber-reinforced polymer (FRP)-confined steel fiber reinforced concrete (SFRC) using a newly developed concrete damage-plasticity approach. Finite element (FE) analysis is conducted based on Lubliner’s model. The new concrete damage-plasticity approach accurately incorporates the effects of the steel fiber volume fraction and aspect ratio, confinement level, concrete strength, and nonlinear dilation behavior of confined concrete. New failure surface and flow rule were established using the experimental database. In order to validate the damage-plasticity model, the predictions from the FE analysis are compared with both experimental results and predictions of an accurate existing model for FRP-confined plain concrete. The analysis results indicate that the proposed approach accurately predicts the compressive behavior of FRP-confined SFRC.
Publisher: Emerald
Date: 22-03-2013
DOI: 10.1108/17260531311309125
Abstract: The purpose of this paper is to present weighted residual method (WRM) for evaluating d ing ratio of unreinforced glued‐laminated (glulam) wood beams and also reinforced glulam beams with E‐glass reinforced epoxy polymer (GRP) plates. In this method, created error from the regression curve to the peak points of experimental displacement values is minimized. Several weight functions such as Galerkin weight function, Petrov‐Galerkin weight functions, and least square weight function are used for minimizing this error and results from these methods are compared to the existing methods as logarithmic decrement analysis (LDA), Hilbert transform analysis (HTA), moving block analysis (MBA), and half power bandwidth (HPB). Because WRM tries to minimize the error function provided from differences between theoretical and experimental fitted curves, comparison among these methods indicate that proposed procedure is useful for any range of d ing ratios and it gives better values in comparison with the other methods. Due to the initial conditions and weight function used in Galerkin weighted residual method, d ing ratio values obtained from this method have different values from the other weighted residual methods. Among the existing methods, HPB method could not predict d ing ratio of the glulam beams accurately. This paper is a high quality research paper that presents weighted residual method (WRM) for evaluating d ing ratio of unreinforced glued‐laminated (glulam) wood beams and also reinforced glulam beams with E‐glass reinforced epoxy polymer (GRP) plates. In this paper, LDA, HTA, MBA, and HPB methods are used and an analytical investigation of d ing ratios of glulam beams unreinforced and reinforced with GRP plates is proposed by using weighted residual method (WRM). Although there is a simplifier assumption in some of existing methods, proposed method shows the d ing ratio can be calculated without any requirement to simplifier assumption.
Publisher: MDPI AG
Date: 23-03-2020
Abstract: In this paper compressive strength and ultimate strain results in the current database of fiber-reinforced polymer (FRP)-confined concrete are used to determine the reliability of their design space. The Lognormal, Normal, Frechet, Gumbel, and Weibull distributions are selected to evaluate the probabilistic characteristics of six FRP material categories. Following this, safety levels of the database are determined based on a probabilistic model. An iterative reliability method is developed with conjugate search direction for evaluating the reliability. The results show that Lognormal and Gumbel distributions provide best probability distribution for model errors of strength and strain enhancement ratios. The developed conjugate reliability method provides improved robustness over the existing reliability methods owing to its faster convergence to stable results. The results reveal that the part of the database containing normal strength concrete (NSC) heavily confined (i.e., actual confinement ratio (flu,a/f’co) 0.5) by low and normal modulus carbon fibers (i.e., fiber elastic modulus (Ef) ≤ 260 GPa) and moderately confined (i.e., 0.3 ≤ flu,a/f’co ≤ 0.5) by aramid fibers exhibits a very high safety level. The segments of the database with a low and moderate safety level have been identified as i) NSC moderately and heavily confined by higher modulus glass fibers (i.e., Ef 60 GPa), ii) high strength concrete (HSC) moderately and heavily confined (i.e., flu,a/f’co 0.3) by glass fibers, iii) HSC lightly confined (i.e., flu,a/f’co ≤ 0.2) by carbon fibers, and iv) HSC lightly confined by aramid fibers. Additional experimental studies are required on these segments of the database before they can be used reliably for design and modeling purposes.
Publisher: MDPI AG
Date: 30-07-2021
DOI: 10.3390/MA14154264
Abstract: Development of sustainable concrete as an alternative to conventional concrete helps in reducing carbon dioxide footprint associated with the use of cement and disposal of waste materials in landfill. One way to achieve that is the use of fly ash (FA) as an alternative to ordinary Portland cement (OPC) because FA is a pozzolanic material and has a high amount of alumina and silica content. Because of its excellent mechanical properties, several studies have been conducted to investigate the use of alkali-activated FA-based concrete as an alternative to conventional concrete. FA, as an industrial by-product, occupies land, thereby causing environmental pollution and health problems. FA-based concrete has numerous advantages, such as it has early strength gaining, it uses low natural resources, and it can be configurated into different structural elements. This study initially presents a review of the classifications, sources, chemical composition, curing regimes and clean production of FA. Then, physical, fresh, and mechanical properties of FA-based concretes are studied. This review helps in better understanding of the behavior of FA-based concrete as a sustainable and eco-friendly material used in construction and building industries.
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 07-2020
Publisher: Informa UK Limited
Date: 03-2013
Publisher: Elsevier BV
Date: 10-2020
Publisher: MDPI AG
Date: 04-12-2022
DOI: 10.3390/SU151411045
Abstract: Recent growth in materials science and engineering technologies has pushed the construction industry to engage in new applications, such as the manufacturing of smart and electrically conductive products. Such novel uses of conductive construction materials would potentially allow their use in conjunction with various fields, such as those referred to as “Industry 4.0.” The following study uses iron oxide (Fe3O4)-multi-walled carbon nanotubes (MWCNTs) nanocomposites synthesized by chemical vapor deposition (CVD) and incorporated into the cementitious mortars as a substitute for sand at 1, 2, and 3% ratios to enhance the electrical conductivity. Results reveal that the electrical resistivity of cementitious composites decreases (due to the increase in electrical conductivity) from 208.3 to 61.6 Ω·m with both the Fe3O4-MWCNTs nanocomposites ratio and the increasing voltage. The lowest compressive strengths at 7 and 28 days are 12.6 and 17.4 MPa for specimens with 3% Fe3O4-MWCNTs and meet the standards that comply with most applications. On the other hand, the highest porosity was reached at 26.8% with a Fe3O4-MWCNTs rate of 3%. This increase in porosity caused a decrease in both the dry unit weight and ultrasonic pulse velocity (from 5156 to 4361 m/s). Further, it is found that the incorporation of Fe3O4-MWCNT nanocomposites can have a negative effect on the hardening process of mortars, leading to localized air cavities and an inhomogeneous development of cementing products. Nonetheless, the improvement of the electrical conductivity of the s les without significantly compromising their physico-mechanical properties will allow their use in various fields, such as deicing applications with low-voltage electric current.
Publisher: American Society of Civil Engineers (ASCE)
Date: 12-2016
Publisher: Informa UK Limited
Date: 04-03-2020
Publisher: Elsevier BV
Date: 12-2023
No related grants have been discovered for Aliakbar Gholampour.