Ali Mirgozar | Islamic Azad University of Fouman and Shaft (original) (raw)
Papers by Ali Mirgozar
The durability of reinforced concrete structures is one of the major problems confronting the con... more The durability of reinforced concrete structures is one of the major problems confronting the construction industry, leading to significant costs of repair and remediation. The factors that are generally associated with high rates of corrosion of steel in concrete are the presence of excessive chloride contamination in the material or penetration of chloride in concretes which are exposed to saltwater. A lot of international investigations are being done in this case, however there still remain many problems that have not been solved yet. Nowadays lightweight concrete is being used for both structural and non-structural applications. As a structural material it should have specific characteristics to meet both the strength and durability for the long term of use. Expanded polystyrene is a stable low density foam of nonabsorbent, hydrophobic, closed cell nature that can be used as ultra lightweight aggregate suitable for developing concretes for both structural and non-structural app...
Construction and Building Materials, 2012
Construction and Building Materials, 2013
The durability of reinforced concrete structures is one of the major problems confronting the con... more The durability of reinforced concrete structures is one of the major problems confronting the construction industry, leading to significant costs of repair and remediation. The factors that are generally associated with high rates of corrosion of steel in concrete are the presence of excessive chloride contamination in the material or penetration of chloride in concretes which are exposed to saltwater. A lot of international investigations are being done in this case, however there still remain many problems that have not been solved yet. Nowadays lightweight concrete is being used for both structural and non-structural applications. As a structural material it should have specific characteristics to meet both the strength and durability for the long term of use. Expanded polystyrene is a stable low density foam of non-absorbent, hydrophobic, closed cell nature that can be used as ultra lightweight aggregate suitable for developing concretes for both structural and non-structural applications by varying its volume percentage in concrete.
The use of lightweight concrete in many applications of modern construction is increasing, owing ... more The use of lightweight concrete in many applications of modern construction is increasing, owing to the advantages that lower density results in decreasing the magnitude of dead load of the structure which lead to smaller cross sections for load bearing elements. Expanded polystyrene (EPS) beads are a type of artificial lightweight nonabsorbent aggregates which can be used to produce low density concretes by replacing with normal aggregates, either partially or fully, depending upon the requirements of density and strength. Also plastic shrinkage is the dimensional change that occurs in all fresh cement based materials within the first few hours after it has been placed which is not unacceptable in itself, but it is some times accompanied by development of cracks that are unsightly and objectionable. Polypropylene and other synthetic fibers are added to concrete as secondary reinforcement in order to control this plastic shrinkage. On the other hand, the addition of fibers affects on the properties of hardened concrete like compressive and tensile strength, elastic modulus and toughness. The present study covers the use of polypropylene fibers at contents equal to 0.1%, 0.3%, 0.5% and 1% by volume of EPS concrete in order to study about the effects of its addition into the EPS concrete matrix on mechanical properties. Also the effects of using Silica fume and Rice husk as two supplementary cementitious materials were investigated.
The main objective of this study is to evaluate the mechanical properties of Expanded polystyrene... more The main objective of this study is to evaluate the mechanical properties of Expanded polystyrene (EPS) concretes containing silica fume and rice husk ash as supplementary cementitious materials reinforced with different volume fractions of polypropylene fibers. The effects of using EPS aggregates and polypropylene fibers on hardened state characteristics of concretes containing silica fume and rice husk ash were evaluated. The obtained results shows improvements in some mechanical properties of EPS concretes by using polypropylene fibers in matrix, mainly in energy absorption capability. Introduction: The uses of lightweight concrete has been increasing due to the advantage of its low density, which results in a significant benefit in terms of load bearing elements of smaller cross section[1]. Expanded polystyrene beads are a type of artificial lightweight, nonabsorbent, closed cell nature aggregate [2,3]. Presently a comprehensive investigation on the mechanical behavior of EPS concretes containing polypropylene fibers is not available. In this study, EPS concretes with different EPS contents, reinforced with various volume fractions of polypropylene fibers were developed. literature suggests the hydrophobic nature of EPS aggregates in these mixes has to be compensated through bonding additives[4]. However, in the present study, no bonding additives were used But the effects of using silica fume and rice husk ash to study the dispersion of EPS and polypropylene fibers in the cement paste and the interfacial bonding were investigated by morphology (SEM).
" For the first time, models developed for prediction of the strength properties of EPS concrete.... more " For the first time, models developed for prediction of the strength properties of EPS concrete. " Robust ANN and ANFIS models proposed for predicting the compressive strength of EPS concrete. " The overall performance of trained ANN is more accurate than ANFIS model. " Such robust models could be easily utilized for EPS concrete mix proportioning as a problem with high complexities included. " Higher accuracy of neural network is due to application of Levenberg–Marquardt backpropagation algorithm. a b s t r a c t EPS concrete is an especial type of lightweight concrete made by partial replacement of concrete's stone aggregates with lightweight expanded polystyrene beads (EPSs). This type of concrete is very sensitive to its constituent materials which complicate the modeling process. Considering the involved complexities, this paper dealt with developing and comparing parametric regression, neural network (ANN) and adap-tive network-based fuzzy inference system (ANFIS) models for predicting the compressive strength of EPS concrete for possible use in mix-design framework. The results emphasized that the elite ANN model constructed with two hidden layers and comprised of three neurons in each layers, could be effectively used for prediction purposes. Moreover, ANFIS elite model developed by bell-shaped membership function was recognized as a proper model to this means; however, its prediction performances were evaluated to be diluted than ANN model. On the other hand, the prediction results of second-order partial polynomial regression model as elite empirical one showed the weakness of this model comparing ANN and ANFIS models.
This paper aims to study the possibility of producing multi-strength grade lightweight concrete c... more This paper aims to study the possibility of producing multi-strength grade lightweight concrete containing expanded polyethylene beads and evaluate their mechanical and durability characteristics. To this aim, various mixtures are produced by replacing 0%, 15%, 25%, 40% and 55% of natural aggregates volume with EPS beads, substituting cement with 10% silica fume (SF) or 20% rice husk ash (RHA), and adding waste propylene fibers in the percentage of 0.1, 0.3, 0.5 and 1 of cement volume (0.013%, 0.038%, 0.063% and 0.127% of concrete volume). These mixtures are evaluated through a comprehensive test program including measuring compressive strength, splitting tensile strength, flexural strength, ultrasonic pulse velocity, drying shrinkage, water absorption and electrical resistivity. Generally, application of EPS beads decreases the strength properties; however, the results show the potential of EPS beads for producing structural grade, moderate strength grade and insulating lightweight concrete. Mixtures containing 15% EPS beads and 20% RHA as well as 25% EPS beads and 10% SF show acceptable strength and density for structural lightweight concrete. In addition, application of 40% and 55% EPS beads lead to the moderate strength grade and insulting lightweight concrete respectively. These results accompany by an improvement in electrical resistivity, and increase in water absorption and drying shrinkage. Moreover, except for toughness, addition of waste fibers has not improved lightweight concrete properties.
The durability of reinforced concrete structures is one of the major problems confronting the con... more The durability of reinforced concrete structures is one of the major problems confronting the construction industry, leading to significant costs of repair and remediation. The factors that are generally associated with high rates of corrosion of steel in concrete are the presence of excessive chloride contamination in the material or penetration of chloride in concretes which are exposed to saltwater. A lot of international investigations are being done in this case, however there still remain many problems that have not been solved yet. Nowadays lightweight concrete is being used for both structural and non-structural applications. As a structural material it should have specific characteristics to meet both the strength and durability for the long term of use. Expanded polystyrene is a stable low density foam of nonabsorbent, hydrophobic, closed cell nature that can be used as ultra lightweight aggregate suitable for developing concretes for both structural and non-structural app...
Construction and Building Materials, 2012
Construction and Building Materials, 2013
The durability of reinforced concrete structures is one of the major problems confronting the con... more The durability of reinforced concrete structures is one of the major problems confronting the construction industry, leading to significant costs of repair and remediation. The factors that are generally associated with high rates of corrosion of steel in concrete are the presence of excessive chloride contamination in the material or penetration of chloride in concretes which are exposed to saltwater. A lot of international investigations are being done in this case, however there still remain many problems that have not been solved yet. Nowadays lightweight concrete is being used for both structural and non-structural applications. As a structural material it should have specific characteristics to meet both the strength and durability for the long term of use. Expanded polystyrene is a stable low density foam of non-absorbent, hydrophobic, closed cell nature that can be used as ultra lightweight aggregate suitable for developing concretes for both structural and non-structural applications by varying its volume percentage in concrete.
The use of lightweight concrete in many applications of modern construction is increasing, owing ... more The use of lightweight concrete in many applications of modern construction is increasing, owing to the advantages that lower density results in decreasing the magnitude of dead load of the structure which lead to smaller cross sections for load bearing elements. Expanded polystyrene (EPS) beads are a type of artificial lightweight nonabsorbent aggregates which can be used to produce low density concretes by replacing with normal aggregates, either partially or fully, depending upon the requirements of density and strength. Also plastic shrinkage is the dimensional change that occurs in all fresh cement based materials within the first few hours after it has been placed which is not unacceptable in itself, but it is some times accompanied by development of cracks that are unsightly and objectionable. Polypropylene and other synthetic fibers are added to concrete as secondary reinforcement in order to control this plastic shrinkage. On the other hand, the addition of fibers affects on the properties of hardened concrete like compressive and tensile strength, elastic modulus and toughness. The present study covers the use of polypropylene fibers at contents equal to 0.1%, 0.3%, 0.5% and 1% by volume of EPS concrete in order to study about the effects of its addition into the EPS concrete matrix on mechanical properties. Also the effects of using Silica fume and Rice husk as two supplementary cementitious materials were investigated.
The main objective of this study is to evaluate the mechanical properties of Expanded polystyrene... more The main objective of this study is to evaluate the mechanical properties of Expanded polystyrene (EPS) concretes containing silica fume and rice husk ash as supplementary cementitious materials reinforced with different volume fractions of polypropylene fibers. The effects of using EPS aggregates and polypropylene fibers on hardened state characteristics of concretes containing silica fume and rice husk ash were evaluated. The obtained results shows improvements in some mechanical properties of EPS concretes by using polypropylene fibers in matrix, mainly in energy absorption capability. Introduction: The uses of lightweight concrete has been increasing due to the advantage of its low density, which results in a significant benefit in terms of load bearing elements of smaller cross section[1]. Expanded polystyrene beads are a type of artificial lightweight, nonabsorbent, closed cell nature aggregate [2,3]. Presently a comprehensive investigation on the mechanical behavior of EPS concretes containing polypropylene fibers is not available. In this study, EPS concretes with different EPS contents, reinforced with various volume fractions of polypropylene fibers were developed. literature suggests the hydrophobic nature of EPS aggregates in these mixes has to be compensated through bonding additives[4]. However, in the present study, no bonding additives were used But the effects of using silica fume and rice husk ash to study the dispersion of EPS and polypropylene fibers in the cement paste and the interfacial bonding were investigated by morphology (SEM).
" For the first time, models developed for prediction of the strength properties of EPS concrete.... more " For the first time, models developed for prediction of the strength properties of EPS concrete. " Robust ANN and ANFIS models proposed for predicting the compressive strength of EPS concrete. " The overall performance of trained ANN is more accurate than ANFIS model. " Such robust models could be easily utilized for EPS concrete mix proportioning as a problem with high complexities included. " Higher accuracy of neural network is due to application of Levenberg–Marquardt backpropagation algorithm. a b s t r a c t EPS concrete is an especial type of lightweight concrete made by partial replacement of concrete's stone aggregates with lightweight expanded polystyrene beads (EPSs). This type of concrete is very sensitive to its constituent materials which complicate the modeling process. Considering the involved complexities, this paper dealt with developing and comparing parametric regression, neural network (ANN) and adap-tive network-based fuzzy inference system (ANFIS) models for predicting the compressive strength of EPS concrete for possible use in mix-design framework. The results emphasized that the elite ANN model constructed with two hidden layers and comprised of three neurons in each layers, could be effectively used for prediction purposes. Moreover, ANFIS elite model developed by bell-shaped membership function was recognized as a proper model to this means; however, its prediction performances were evaluated to be diluted than ANN model. On the other hand, the prediction results of second-order partial polynomial regression model as elite empirical one showed the weakness of this model comparing ANN and ANFIS models.
This paper aims to study the possibility of producing multi-strength grade lightweight concrete c... more This paper aims to study the possibility of producing multi-strength grade lightweight concrete containing expanded polyethylene beads and evaluate their mechanical and durability characteristics. To this aim, various mixtures are produced by replacing 0%, 15%, 25%, 40% and 55% of natural aggregates volume with EPS beads, substituting cement with 10% silica fume (SF) or 20% rice husk ash (RHA), and adding waste propylene fibers in the percentage of 0.1, 0.3, 0.5 and 1 of cement volume (0.013%, 0.038%, 0.063% and 0.127% of concrete volume). These mixtures are evaluated through a comprehensive test program including measuring compressive strength, splitting tensile strength, flexural strength, ultrasonic pulse velocity, drying shrinkage, water absorption and electrical resistivity. Generally, application of EPS beads decreases the strength properties; however, the results show the potential of EPS beads for producing structural grade, moderate strength grade and insulating lightweight concrete. Mixtures containing 15% EPS beads and 20% RHA as well as 25% EPS beads and 10% SF show acceptable strength and density for structural lightweight concrete. In addition, application of 40% and 55% EPS beads lead to the moderate strength grade and insulting lightweight concrete respectively. These results accompany by an improvement in electrical resistivity, and increase in water absorption and drying shrinkage. Moreover, except for toughness, addition of waste fibers has not improved lightweight concrete properties.