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Characteristics of GGBFS-Based Pervious Concrete Considering Rheological Properties of the Binder
Yanchen Oinam,주수환,권성우,신명수,표석훈 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.1
To mitigate environmental challenges, such as urban flooding, noise pollution, and the urban heat island effect, pervious concrete has been developed. This research was intended to develop pervious concrete made from ground granulated blast furnace slag (GGBFS) to further decrease the environmental impact of the construction sector by reducing the content of ordinary Portland cement (OPC). The primary objective of the mix proportion was to maximize water permeability while meeting the required compressive strength. Two levels (60 and 100%) of OPC replacement by GGBFS were evaluated and compared to OPC-only concrete, and two target porosities (10 and 15%) were achieved by modifying the binder-to-aggregate ratio. CaO and CaCl2 were utilized as an activator and an accelerator, respectively, for the GGBFS only binder. Characteristics of the pervious concrete were determined with the compressive strength, porosity and water permeability test. Meanwhile, the effects of the rheological properties of binders on the water permeability and compressive strength of pervious concretes was evaluated. According to the results, the permeability of pervious concretes always exhibited a positive correlation with porosity, regardless of binder type. Although, the pervious concrete made with CaO-activated GGBFS has a lower compressive strength than the other two cases (60% GGBFS and only OPC), it still meets the minimum strength requirement. Based on the rheology studies of binder, it was found that, the adhesion force of the binder and the compressive strength of the pervious concrete decreases, as evaluated by rheology studies on binders. The CT scan revealed that when the adhesive force of the binder was weaker, the local porosity was higher (i.e., pore volume was larger) at the bottom of the specimen, which might be due to the limited consolidation and compaction of the binder between aggregate particles at the bottom due to its higher plastic viscosity.
Development of Carbon-neutral Water-permeable Concrete using Ground Granulated Blast Furnace Slag
Yanchen Oinam(얀첸),Pyo, Sukhoon(표석훈),Shin, Myoungsu(신명수) 한국콘크리트학회 2021 한국콘크리트학회 학술대회 논문집 Vol.33 No.2
Water permeable concrete or pervious concrete has been studied as an ideal water-permeable material to improve various environmental conditions. In this study, a series of experimental research has been conducted to evaluate the mechanical properties, porosity, permeability of permeable concrete using a ground granulated blast furnace slag (GGBFS) based cementless binder and binders partially replaced with GGBFS. Cementless permeable concrete with 12%, 16% of porosity, and 17 MPa, 16 MPa respectively of 7 days compressive strength was developed. For a fair comparison of permeability measurement ASTM C1701, EN 12697-19, and falling head permeability test methods were performed and provided with permeability results within the required range. A rheology test has also been performed to characterize all the paste of different flows to obtain a particular flow that can attain the target porosity without compromising the compressive strength of the concrete, which will be presented in the conference.
Evaluation of seismic strengthening techniques for non-ductile soft-story RC frame
Karki, Prajwol,Oinam, Romanbabu M.,Sahoo, Dipti Ranjan Techno-Press 2020 Advances in concrete construction Vol.9 No.4
Open ground story (OGS) reinforced concrete (RC) buildings are vulnerable to the complete collapse or severe damages under seismic actions. This study investigates the effectiveness of four different strengthening techniques representing the local and global modifications to improve the seismic performance of a non-ductile RC OGS frame. Steel caging and concrete jacketing methods of column strengthening are considered as the local modification techniques, whereas steel bracing and RC shear wall systems are selected as the global strengthening techniques in this study. Performance-based plastic design (PBPD) approach relying on energy-balance concept has been adopted to determine the required design force demand on the strengthening elements. Nonlinear static and dynamic analyses are carried out on the numerical models of study frames to assess the effectiveness of selected strengthening techniques in improving the seismic performance of OGS frame.. Strengthening techniques based on steel braces and RC shear wall significantly reduced the peak interstory drift response of the OGS frame. However, the peak floor acceleration of these strengthened frames is amplified by more than 2.5 times as compared to that of unstrengthened frame. Steel caging technique of column strengthening resulted in a reasonable reduction in the peak interstory drift response without substantial amplification in peak floor acceleration of the OSG frame.
박성우(Park, Sungwoo),얀첸(Oinam, Yanchen),강민창(Kang, Minchang),표석훈(Pyo, Sukhoon) 한국콘크리트학회 2021 한국콘크리트학회 학술대회 논문집 Vol.33 No.2
이 연구는 재료의 진부피 측정방법을 소개한다. 콘크리트 또는 시멘트 재료의 부피 및 밀도 측정을 위한 여러 방법이 개발됐으나, 각 방법은 단점들을 가지고 있다. 예를 들면, 물에 넣어 부피를 측정할 경우, 시편 내에서 화학물질이 추출되어 정확한 측정에 방해가 될 수 있다. 이러한 단점들을 극복하기 위하여 진공을 이용한 진부피 측정 기기를 개발하였으며 시멘트 재료들 성공적으로 측정할 수 있었다. This study introduces an lab-made volume measurement instrument using a vacuum pump. Several methods to measure the porosity of cementitious material such as porous concrete or foamed mortar. However, the previous test methods have some limits. To overcome their disadvantage, this paper proposes a lab-made volume measurement method. This method inherits the principle of a commercial gas pycnometer and results in reasonable results.
Bala, Renu,Srivastava, Amit,Ningthoujam, Gouri Devi,Potsangbam, Thadoi,Oinam, Amita,Anal, Ch Lily The Korean Society for Preventive Medicine 2021 Journal of Preventive Medicine and Public Health Vol.54 No.1
Objectives: The coronavirus disease 2019 (COVID-19) pandemic is a public health emergency posing unprecedented challenges for health authorities. Social media may serve as an effective platform to disseminate health-related information. This study aimed to assess the extent of social media use, its impact on preventive behavior, and negative health effects such as cyberchondria and information overload. Methods: A cross-sectional observational study was conducted between June 10, 2020 and August 9, 2020 among people visiting the outpatient department of the authors' institution, and participants were also recruited during field visits for an awareness drive. Questions were developed on preventive behavior, and the Short Cyberchondria Scale and instruments dealing with information overload and perceived vulnerability were used. Results: The study recruited 767 participants with a mean age of about 45 years. Most of the participants (>90%) engaged in preventive behaviors, which were influenced by the extent of information received through social media platforms (β=3.297; p<0.001) and awareness of infection when a family member tested positive (β=29.082; p<0.001) or a neighbor tested positive (β=27.964; p<0.001). The majority (63.0%) of individuals often searched for COVID-19 related news on social media platforms. The mean±standard deviation scores for cyberchondria and information overload were 9.09±4.05 and 8.69±2.56, respectively. Significant and moderately strong correlations were found between cyberchondria, information overload, and perceived vulnerability to COVID-19. Conclusions: This study provides evidence that the use of social media as an information- seeking platform altered preventive behavior. However, excessive and misleading information resulted in cyberchondria and information overload.