• Advances in nano research
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• v.15 no.5
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• pp.467-484
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• 2023

Despite the significant features of fiber-reinforced cementitious composites (FRCCs), including better mechanical, fractural, and durability performance, their high content of cement has restricted their use in the construction industry. Although ground granulated blast furnace slag (GGBFS) is considered the main supplementary cementitious material, its slow pozzolanic reaction stands against its application. The addition of nano-sized mineral modifiers, including nano-silica (NS), is an alternative to address the drawbacks of using GGBFS. The main object of this empirical and numerical research is to examine the effect of NS on the strain-hardening behavior of cementitious composites; ten mixes were designed, and five levels of NS were considered. This study proposes a new method, using a four-point bending test to assess the use of nano-silica (NS) on the flexural behavior, first cracking strength, fracture energy, and micromechanical parameters including interfacial friction bond strength and maximum bridging stress. Digital image correlation (DIC) was used for monitoring the initiation and propagation of the cracks. In addition, to attain a deep comprehension of fiber/matrix interaction, scanning electron microscope (SEM) analysis was used. It was discovered that using nano-silica (NS) in cementitious materials results in an enhancement in the matrix toughness, which prevents multiple cracking and, therefore, strain-hardening. In addition, adding NS enhanced the interfacial transition zone between matrix and fiber, leading to a higher interfacial friction bond strength, which helps multiple cracking in the composite due to the hydrophobic nature of polypropylene (PP) fibers. The findings of this research provide insight into finding the optimum percent of NS in which both ductility and high tensile strength of the composites would be satisfied. As a concluding remark, a new criterion is proposed, showing that the optimum value of nano-silica is 2%. The findings and proposed method of this study can facilitate the design and utilization of green cementitious composites in structures.

• Korean Journal of Culture and Social Issue
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• v.14 no.1_spc
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• pp.427-468
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• 2008

This article examines the role and influence of educational achievement on Korean society and its future. Four major factors that associated with and influence educational achievement in Korea (i.e., trust, efficacy beliefs, quality of life, and societal transformation) are reviewed. First, the role of educational achievement on establishing a basis for trust in Korean society is examined. By reviewing studies of perception of Korean society, people and institutions, the importance of establishing trust in Korean society is outlined. Second, the role of efficacy belief in promoting educational achievement is examined. The importance of collective efficacy, at the adolescent, adult and political levels is emphasized. In addition, the concept and application of self-efficacy for teachers and parents is reviewed. Third, the role and influence of educational achievement on quality of life is outlined. Studies indicate that educational achievement plays an important role in improving the quality of life. The pressure to achieve, however, can have negative impact on stress and mental health and support systems need to be developed to alleviate their impact. Fourth, the future and prospects for Korean society through educational achievement is discussed. Through education, the importance of bridging the divide with North Korea is an important agenda for the future of Korean society. Finally, the importance of indigenous psychological perspective in understanding Korean society and providing direction for the future is discussed.