The reduction of the moisture content of concrete during the drying process reduces the concrete’... more The reduction of the moisture content of concrete during the drying process reduces the concrete’s volume and causes it to shrink. In general, concrete shrinkage is a phenomenon that causes concrete volume to dwindle and can lead to durability problems. There are different types of this phenomenon, among them chemical shrinkage, autogenous shrinkage, drying shrinkage including free shrinkage and restrained shrinkage, and thermal contraction. Shrinkage-reducing admixtures are commercially available in different forms. The present study investigates the effect of liquid propylene glycol ether on mechanical properties and free shrinkage induced by drying at different water-cement (w/c) ratios. Furthermore, the effect of shrinkage-reducing admixtures on the properties of hardened concrete such as compressive and tensile strength, electrical resistivity, modulus of elasticity, free drying shrinkage, water absorption, and depth of water penetration was investigated. The results indicated ...
ABSTRACT The main purpose of this study includes investigation of the rheological properties of f... more ABSTRACT The main purpose of this study includes investigation of the rheological properties of fresh self consolidating cement paste containing chemical and mineral additives using Artificial Neural Network (ANN) model. In order to develop the model, 200 different mixes are cast in the laboratory as a part of an extensive experimental research program. The data used in the ANN model are arranged in a format of fourteen input parameters covering water-binder ratio, four different mineral additives (calcium carbonate, metakaolin, silica fume, and limestone), five different superplasticizers based on the poly carboxylate and naphthalene and four different Viscosity Modified Admixtures (VMAs). Two common output parameters including the mini slump value and flow cone time are chosen for measuring the rheological properties of fresh self consolidating cement paste. Having validated the model, the influence of effective parameters on the rheological properties of fresh self consolidating cement paste is investigated based on the ANN model outputs. The output results of the model are then compared with the results of previous studies performed by other researchers. Ultimately, the analysis of the model outputs determines the optimal percentage of additives which has a strong influence on the rheological properties of fresh self consolidating cement paste. The proposed ANN model shows that metakaolin and silica fume affect the rheological properties in the same manner. In addition, for providing the suitable rheological properties, the ANN model introduces the optimal percentage of metakaolin, silica fume, calcium carbonate and limestone as 15, 15, 20 and 20% by cement weight, respectively.
Prediction of creep was improved using proposed inverse analysis methodology. Sample results from... more Prediction of creep was improved using proposed inverse analysis methodology. Sample results from different studies were used to verify proposed methodology. Various statistical indicators were used to evaluate the accuracy of proposed method. Proposed method had lower prediction errors compared to available creep models. For certain creep models, the proposed method was too sensitive and thus not appropriate. a b s t r a c t Long-term creep prediction has been a major issue of concern in designing concrete structures for some time. Many researchers have developed various models in order to predict uni-axial compressive concrete creep, however a more precise and reliable method of prediction is still required. This investigation introduces an inverse analysis (IA) method that utilizes short-term creep measurements under certain conditions to predict long-term results under the same conditions. The proposed IA method was applied to seven different prediction models and the experimental results of six specimens (from three different studies) were chosen to verify the reliability of this method. It was concluded that the IA method is able to successfully improve the accuracy of prediction and has a comprehensive range of application.
Journal of Performance of Constructed Facilities, Aug 17, 2012
A detailed investigation was carried out on a 50-year-old reinforced concrete jetty in a commerci... more A detailed investigation was carried out on a 50-year-old reinforced concrete jetty in a commercial port of Iran to assess the long-term performance as well as the structural condition. Destructive and nondestructive tests such as carbonation depth, electrical resistivity, chloride diffusion, X-ray diffraction, compressive strength, and water absorption were performed. The results revealed that the good quality of the concrete has protected reinforcement from corrosion. However, structural analysis showed minor weakness in some elements of the jetty; thus, consulting engineers finally decided to strengthen some elements with fiber-reinforced polymers.
ABSTRACT Concrete durability in different environment conditions especially in marine climate is ... more ABSTRACT Concrete durability in different environment conditions especially in marine climate is always one of the important characteristic in choosing a specific mixture for it. Every year, deterioration of the concrete structures-which is mainly due to chloride induced corrosion of embedded steel bars- imposes hundreds of million dollars cost for these structures. So it is essential to select the suitable concrete materials to match the exposure severity and to adopt proper construction practices to obtain a high quality durable concrete. In this paper four different concrete mixtures are designed for investigation of efficiency of silica fume (SF) and ground granulated of blast furnace slag (GGBS). These mixtures were assessed in four parts: Water absorption, Chloride diffusion, Oxygen permeability and Chloride diffusion which are the most important features of durability. The results of this study indicate that the durability performance of concrete with pozzolanic materials is higher than control concrete meanwhile Using combination of SF and GGBS shows better results than other concrete mixtures.
DuraBility-BaSED DESiGn In marine areas, chloride ion exposure is the main cause of corrosion of ... more DuraBility-BaSED DESiGn In marine areas, chloride ion exposure is the main cause of corrosion of embedded steel bars within concrete structures. Extensive studies have evaluated the effects of different parameters on chloride penetration into concrete, so it's now possible to ...
The reduction of the moisture content of concrete during the drying process reduces the concrete’... more The reduction of the moisture content of concrete during the drying process reduces the concrete’s volume and causes it to shrink. In general, concrete shrinkage is a phenomenon that causes concrete volume to dwindle and can lead to durability problems. There are different types of this phenomenon, among them chemical shrinkage, autogenous shrinkage, drying shrinkage including free shrinkage and restrained shrinkage, and thermal contraction. Shrinkage-reducing admixtures are commercially available in different forms. The present study investigates the effect of liquid propylene glycol ether on mechanical properties and free shrinkage induced by drying at different water-cement (w/c) ratios. Furthermore, the effect of shrinkage-reducing admixtures on the properties of hardened concrete such as compressive and tensile strength, electrical resistivity, modulus of elasticity, free drying shrinkage, water absorption, and depth of water penetration was investigated. The results indicated ...
ABSTRACT The main purpose of this study includes investigation of the rheological properties of f... more ABSTRACT The main purpose of this study includes investigation of the rheological properties of fresh self consolidating cement paste containing chemical and mineral additives using Artificial Neural Network (ANN) model. In order to develop the model, 200 different mixes are cast in the laboratory as a part of an extensive experimental research program. The data used in the ANN model are arranged in a format of fourteen input parameters covering water-binder ratio, four different mineral additives (calcium carbonate, metakaolin, silica fume, and limestone), five different superplasticizers based on the poly carboxylate and naphthalene and four different Viscosity Modified Admixtures (VMAs). Two common output parameters including the mini slump value and flow cone time are chosen for measuring the rheological properties of fresh self consolidating cement paste. Having validated the model, the influence of effective parameters on the rheological properties of fresh self consolidating cement paste is investigated based on the ANN model outputs. The output results of the model are then compared with the results of previous studies performed by other researchers. Ultimately, the analysis of the model outputs determines the optimal percentage of additives which has a strong influence on the rheological properties of fresh self consolidating cement paste. The proposed ANN model shows that metakaolin and silica fume affect the rheological properties in the same manner. In addition, for providing the suitable rheological properties, the ANN model introduces the optimal percentage of metakaolin, silica fume, calcium carbonate and limestone as 15, 15, 20 and 20% by cement weight, respectively.
Prediction of creep was improved using proposed inverse analysis methodology. Sample results from... more Prediction of creep was improved using proposed inverse analysis methodology. Sample results from different studies were used to verify proposed methodology. Various statistical indicators were used to evaluate the accuracy of proposed method. Proposed method had lower prediction errors compared to available creep models. For certain creep models, the proposed method was too sensitive and thus not appropriate. a b s t r a c t Long-term creep prediction has been a major issue of concern in designing concrete structures for some time. Many researchers have developed various models in order to predict uni-axial compressive concrete creep, however a more precise and reliable method of prediction is still required. This investigation introduces an inverse analysis (IA) method that utilizes short-term creep measurements under certain conditions to predict long-term results under the same conditions. The proposed IA method was applied to seven different prediction models and the experimental results of six specimens (from three different studies) were chosen to verify the reliability of this method. It was concluded that the IA method is able to successfully improve the accuracy of prediction and has a comprehensive range of application.
Journal of Performance of Constructed Facilities, Aug 17, 2012
A detailed investigation was carried out on a 50-year-old reinforced concrete jetty in a commerci... more A detailed investigation was carried out on a 50-year-old reinforced concrete jetty in a commercial port of Iran to assess the long-term performance as well as the structural condition. Destructive and nondestructive tests such as carbonation depth, electrical resistivity, chloride diffusion, X-ray diffraction, compressive strength, and water absorption were performed. The results revealed that the good quality of the concrete has protected reinforcement from corrosion. However, structural analysis showed minor weakness in some elements of the jetty; thus, consulting engineers finally decided to strengthen some elements with fiber-reinforced polymers.
ABSTRACT Concrete durability in different environment conditions especially in marine climate is ... more ABSTRACT Concrete durability in different environment conditions especially in marine climate is always one of the important characteristic in choosing a specific mixture for it. Every year, deterioration of the concrete structures-which is mainly due to chloride induced corrosion of embedded steel bars- imposes hundreds of million dollars cost for these structures. So it is essential to select the suitable concrete materials to match the exposure severity and to adopt proper construction practices to obtain a high quality durable concrete. In this paper four different concrete mixtures are designed for investigation of efficiency of silica fume (SF) and ground granulated of blast furnace slag (GGBS). These mixtures were assessed in four parts: Water absorption, Chloride diffusion, Oxygen permeability and Chloride diffusion which are the most important features of durability. The results of this study indicate that the durability performance of concrete with pozzolanic materials is higher than control concrete meanwhile Using combination of SF and GGBS shows better results than other concrete mixtures.
DuraBility-BaSED DESiGn In marine areas, chloride ion exposure is the main cause of corrosion of ... more DuraBility-BaSED DESiGn In marine areas, chloride ion exposure is the main cause of corrosion of embedded steel bars within concrete structures. Extensive studies have evaluated the effects of different parameters on chloride penetration into concrete, so it's now possible to ...
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Papers by Mohammad Shekarchi