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Shrinkage behavior of self-compacting concrete

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第6期13卷 407-419页

作者： Farhad ASLANI shami nejadi Centre for Built Infrastructure Research School of Civil and Environmental Engineering University of Technology Sydney Australia

In the structures where long-term behavior should be monitored and controlled, creep and shrinkage effects have to be included precisely in the analysis and design procedures. Shrinkage varies with the constituent and mixture proportions, and depends on the curing conditions and the work environment as well. Self-compacting concrete (SCC) contains combinations of various components, such as aggregate, cement, superplasticizer, water-reducing agent and other ingredients which affect the properties of the SCC including shrinkage. Hence, the realistic prediction shrinkage strains of SCC are an important requirement of the design process for this type of concrete structures. This study reviews the accuracy of the conventional concrete (CC) shrinkage prediction models proposed by the international codes of practice, including CEB-FIP (1990), ACI 209R (1997), Eurocode 2 (2001), JSCE (2002), AASHTO (2004; 2007) and AS 3600 (2009). Also, SCC shrinkage prediction models proposed by Poppe and De Schutter (2005), Larson (2007), Cordoba (2007) and Khayat and Long (2010) are reviewed. Further, a new shrinkage prediction model based on the comprehensive analysis on both of the available models, i.e., the CC and the SCC is proposed. The predicted shrinkage strains are compared with the actual measured shrinkage strains in 165 mixtures of SCC and 21 mixtures of CC.

关键词： Self-compacting concrete (SCC) Conventional concrete (CC) Shrinkage Long-term behavior Concrete structures

Instantaneous deflection of Iight-weight^concrete slabs

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Frontiers of Earth Science 2017年第4期11卷 412-423页

作者： Behnam VAKHSHOURI shami nejadi Centre for Built Infrastructure Research (CBIR) University of Technology Sydney (UTS) P.O. Box 123 Sydney Australia

Construction loading before the age of 28 d can have the most significant effects on the slabs, especially for multi-story structures. The changing properties of the young concrete complicate the prediction of serviceability design requirements also. An experimental investigation is performed on four simply supported Light-Weight Concrete （LWC） one-way slabs subjected to immediate loading at 14 d. Effects of aggregate type, loading levels and cracking moment together with the influences of ultimate moment capacity and service moment on the instantaneous deflection of slabs are studied. Comparison of the obtained results with predictions of existing models in the literature shows considerable differences between the recorded and estimated instantaneous deflection of LWC slabs. Based on sensitivity analysis of the effective parameters, a new equation is proposed and verified to predict the instantaneous deflection of LWC slabs subjected to loading at the age of 14 d.

关键词： instantaneous deflection light-weight concrete expanded polystyrene effective moment of inertia crackingmoment moment capacity service moment

Creep and Shrinkage Self-Compacting Concrete （SCC） Analytical Models

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Journal of Civil Engineering and Architecture 2012年第1期6卷 93-100页

作者： Farhad Aslani shami nejadi Centre for Built Infrastructure Research School of Civil and Environmental Engineering University of Technology Sydney

In the structures whose long-term behavior should be monitored and controlled, creep and shrinkage effects have to be included precisely in the analysis and design procedures. Creep and shrinkage, vary with the constituent and mixtures proportions, and depend on the curing conditions and work environment as well. Self-compacting concrete （SCC） contains combinations of various components, such as aggregate, cement, superplasticizer, water-reducing agent and other ingredients which affect the properties of the SCC including creep and shrinkage of the SCC. Hence, the realistic prediction creep and shrinkage strains of SCC are an important requirement of the design process of this type of concrete structures. In this study, three proposed creep models and four shrinkage models available in the literature are compared with the measured results of 52 mixtures for creep and 165 mixtures for shrinkage of SCC. The influence of various parameters, such as mixture design, cement content, filler content, aggregate content, and water cement ratio （w/c） on the creep and shrinkage of SCC are also compared and discussed.

关键词： Self-compacting concrete (SCC) conventional concrete (CC) creep shrinkage long-term behavior.

Investigation in Mathematical Models of Chloride Diffusion Coefficient in Concrete Exposed to Marine Environment

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Journal of Civil Engineering and Architecture 2014年第4期8卷 456-463页

作者： Farhad Nabavi shami nejadi Bijan Samali School of Civil and Environmental Engineering University of Technology Sydney Sydney 2007 Australia

Degradation of RC （reinforced concrete） in maritime structures has become a worldwide problem due to its excessive costs of maintenance, repair and replacement in addition to its environmental impacts and safety issues. Degradation of both concrete and steel which is the main reason of reduction in the service life of RC structures strongly depends on the diffusion process of moisture and aggressive species. In this paper, the major and popular mathematical models of diffusion process in concrete are surveyed and investigated. Predominantly in these models, the coefficient of chloride diffusion into the concrete is assumed to be constant. Whereas, experimental records indicate that diffusion coefficient is a function of time. Subsequently, data analysis and comparisons between the existing analytical models for predicting the diffusion coefficient with the existing experimental database are carried out in this study. Clearly, these comparisons reveal that there are gaps between the existing mathematical models and previously recorded experimental results. Perhaps, these gaps may be interpreted as influence of the other affecting parameters on the diffusion coefficient such as temperature, aggregate size and relative humidity in addition to the water cement ratio. Accordingly, the existing mathematical models are not adequate enough to predict the diffusion coefficient precisely and further studies need to be performed.

关键词： Chloride diffusion coefficient corrosion of steel in concrete mathematical model of diffusion.

A review of Acanthamoeba keratitis in the Middle East and Iran

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Journal of Acute Disease 2019年第4期8卷 133-141页

作者： Mohammad Hossein Feiz Haddad Azar Shokri Habib Habibpour Seyede Manizhe Heidar nejadi Infectious and Tropical Diseases Research Center Health Research InstituteAhvaz Jundishapur University of Medical SciencesAhvazIran Department of Parasitology Faculty of MedicineAhvaz Jundishapur University of Medical SciencesAhvazIran Vector-borne Disease Research Center North Khorasan University of Medical SciencesBojnurdIran Student Research Committee Ahvaz Jundishapur University of Medical SciencesAhvazIran Department of Parasitology Faculty of MedicineAhvaz Jundishapur University of Medical SciencesAhvazIran Shoushtar Faculty of Medical Sciences ShoushtarIran

Acanthamoeba keratitis, a vision-threatening disease, is caused by a free-living amoeba of genus Acanthamoeba. Amoeba is widely distributed all around the world. Several cases of Acanthamoeba keratitis have been reported from the Middle East and Iran as well. The infection is mainly caused by inappropriate use of contact lens;therefore, it is more common among lens wearers. The number of reported cases worldwide is increasing annually due to the increasing number of contact lens wearers for medical or cosmetic reasons. It is known that early diagnosis and treatment can reduce consequent damages, while the delay in these processes will deteriorate the vision. Nowadays contact lens wearing, surgery and use of corticosteroids are known to predispose to Acanthamoeba keratitis, and it was also believed that trauma was the main cause. Increasing public knowledge about Acanthamoeba infection, inquiring the history of patients, clinical signs and laboratory findings can be helpful to early diagnosis and better treatment. Regardless of the increasing knowledge of diagnosis and treatment, this disease is still a challenge. Considering the long curative time, and insufficient efficacy of available treatments, it seems that the prevention is more important than the treatment. This review aimed to explain Acanthamoeba keratitis in the Middle East and Iran from the aspects of epidemiology, diagnosis, and therapeutic treatment.

关键词： Acanthamoeba keratitis Diagnosis Therapy Middle East Iran