Influence of pozzolans on properties of cementitious materials: A review

Garg, Rishav,Garg, Rajni,Eddy, Nnabuk Okon Techno-Press 2021 Advances in nano research Vol.11 No.4

Use of additives/supplementary materials in partial substitution of cement is gaining widespread attention across the world due to the sustainability issue with production of cement. With their pozzolanic activity & filler effect, use of nano-pozzolans such as nano-silica has been proved as quite promising & cost-effective for use as supplementary cementitious materials. This study is aimed at highlighting the effect of partial substitution of cement/addition of various nano-pozzolans on the hydration, strength and microstructure of the cementitious materials. Further, the effect of incorporation of other pozzolans has also been discussed. Comparative account of pozzolanic activity of different pozzolans has also been critically analyzed. It has been found that the cement matrix gets improved in terms of its microstructure by partial substitution of cement/addition of pozzolan in appropriate amount resulting in enhancement of the bulk properties by consumption of portlandite. The improved compressive strength of cementitious materials not only results in enhancement of the durability but also the service life of the construction structures and results in reduction of the cost incurred in maintenance and repair. Thus, the cement demand can be decreased by the partial substitution of cement/addition of such materials. It will result in an ultimate reduction of the greenhouse effect and lead to sustainable development.

Experimental Investigation of Electrochemical Corrosion and Chloride Penetration of Concrete Incorporating Colloidal Nanosilica and Silica Fume

Garg, Rishav,Garg, Rajni,Singla, Sandeep The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.4

Enhancement of durability and reduction of maintenance cost of concrete, with the implementation of various approaches, has always been a matter of concern to researchers. The integration of pozzolans as a substitute for cement into the concrete is one of the most desirable technique. Silica fume (SF) and colloidal nanosilica (CS) have received a great deal of interest from researchers with their significant performance in improving the durability of concrete. The synergistic role of the micro and nano-silica particles in improving the main characteristics of cemented materials needs to be investigated. This work aims to examine the utility of partial substitution of cement by SF and CS in binary and ternary blends in the improvement of the durability characteristics linked to resistance for electrochemical corrosion using electrical resistivity and half-cell potential analysis and chloride penetration trough rapid chloride penetration test. Furthermore, the effects of this silica mixture on the compressive strength of concrete under normal and aggressive environment have also been investigated. Based on the maximum compression strength of the concrete, the optimal cement substituent ratios have been obtained as 12% SF and 1.5% CS for binary blends. The optimal CS and SF combination mixing ratios has been obtained as 1.0% and 12% respectively for ternary blends. The ternary blends with substitution of cement by optimal percentage of CS and SF exhibited decreased rate for electrochemical corrosion. The strength and durability studies were found in consistence with the microstructural analysis signifying the beneficiary role of CS and SF in upgrading the performance of concrete.

Manganese(II) and Dioxomolybdenum(VI) Complexes with Monobasic Bidentate Schiff Bases : Synthesis, Characterization and Biological Investigation

Garg, Rekha,Kumari, Anita,Joshi, S.C.,Fahmi, Nighat Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.8

A new series of Mn(II) and Mo(VI) complexes containing the Schiff bases hydrazinecarbothioamide and hydrazinecarboxamide of 5,6-dimethyl-1H-indol-2,3-dione have been synthesized. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, molecular weight determinations and spectral studies viz. electronic IR, ESR, $^1H$ NMR and $^{13}C$ NMR and X-ray diffraction spectral studies. The magnetic moment values of the manganese(II) complexes are in the range of 5.80-6.15 B.M. suggesting a high spin state of manganese in these complexes. The spectral data are consistent with a tetrahedral geometry around Mn(II) and an octahedral geometry for Mo(VI), in which the ligands act as bidentate chelating agents, coordinated through the nitrogen and sulfur/oxygen atoms. The ligands and their metal complexes have been tested against a number of pathogenic fungi and bacteria at different concentrations and were found to possess sufficient fungicidal and bactericidal properties. Further, the complexes were also tested for their antifertility activity in male albino rats and the results were indeed positive.

Design and simulation of an RCN Controller to improve steady state behavior of a self-excited induction generator

Garg, Anjali,Sandhu, Kanwarjit Singh,Saini, Lalit Mohan Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.4

Self-excited induction generators (SEIG) are gaining importance as compared to conventional generators due to their capability toconvert wind energy into electrical energy for a wide range of variation in operating speed. The performance of such a generator depends upon the load, rotor speed and excitation capacitance. Therefore, depending upon the operating conditions, the output voltage and frequency of this machine goes on changing and this imposes a restriction on its usage. In order to maintain constant voltage and frequency, it need controllers, which make the circuit complicated and also increases the overall cost of power generation. This paper presents a simple controller to regulate the output voltage and frequency of SEIG for variation in its operating conditions due to any change in load, rotor speed and excitation capacitance (R, N, C) and their combination. The controller presented is simple in design, user friendly and is also less expensive, as the elements used in the controller are only resistors, inductors and capacitors. A block of SEIG for steady state operation is also modeled and presented in this paper. SEIG, Controller and other components are modeled and simulated using Matlab/Simulink.

Proline-based polymeric monoliths: Synthesis, characterization, and applications as organocatalysts in aldol reaction

Garg, Dipti,Ahn, J.-H.,Chauhan, Ghanshyam S. Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of polymer science Part A, Polymer chemist Vol.48 No.5

<P>Proline-based polymer monoliths were synthesized via green protocol using lipase-catalyzed esterification of methacrylic acid and 4-hydroxyproline. Prolinyl methacrylate thus prepared was polymerized in situ as crosslinked monolith. The monolith was characterized by various techniques such as Fourier transform infrared, <SUP>1</SUP>H-NMR, <SUP>13</SUP>C-NMR, scanning electron microscopy (SEM), X-ray diffraction (XRD), and nitrogen analysis and used as catalyst in aldol reactions. The swelling behavior of the monolith was also studied as function of various external parameters like pH and temperature. The monoliths synthesized with 1% crosslinker was selected as candidate monolith for use as catalyst in aldol reaction, which was studied as a function of time, temperature, substrate structure, and amount of water:EtOH. The catalysts exhibited high efficiency in the cross aldol reaction, especially with the aromatic substrates having electron withdrawing substituent, and also good activity retention was observed when recycleability was studied up to five cycles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1007–1015, 2010</P> <B>Graphic Abstract</B> <P>Proline-based polymer monoliths were synthesized via green protocol using lipase-catalyzed esterification of methacrylic acid and 4-hydroxyproline. The monomer was polymerized to polymer monoliths, and the latter were used as heterogeneous polymer catalysts in the aldol reaction that was studied in three forms viz. simple aldol, cross aldol, and ketone-aldehyde reaction. The catalysts exhibited high efficiency in the cross aldol reaction, especially with the aromatic substrates having electron withdrawing substituent, and reasonable retention of catalytic efficiency up to five cycles. <img src='wiley_img/0887624X-2010-48-5-POLA23845-gra001.gif' alt='wiley_img/0887624X-2010-48-5-POLA23845-gra001'> </P>

Effect of Non-Idealities on the Design and Performance of a DC-DC Buck Converter

Garg, Man Mohan,Pathak, Mukesh Kumar,Hote, Yogesh Vijay The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

In this study, the performance of a direct current (DC)-DC buck converter is analyzed in the presence of non-idealities in passive components and semiconductor devices. The effect of these non-idealities on the various design issues of a DC-DC buck converter is studied. An improved expression for duty cycle is developed to compensate the losses that occur because of the non-idealities. The design equations for inductor and capacitor calculation are modified based on this improved expression. The effect of the variation in capacitor equivalent series resistance (ESR) on output voltage ripple (OVR) is analyzed in detail. It is observed that the value of required capacitance increases with ESR. However, beyond a maximum value of ESR (r_c,max), the capacitor is unable to maintain OVR within a specified limit. The expression of r_c,max is derived in terms of specified OVR and inductor current ripple. Finally, these theoretical studies are validated through MATLAB simulation and experimental results.

Bypass Fat Production Using Acid Oil, Its Effect on In Vitro Rumen Fermentation and Effect of Its Feeding on In Sacco DM Disappearance in Sheep

Garg, M.R. Asian Australasian Association of Animal Productio 1997 Animal Bioscience Vol.10 No.6

Attempts were made in the laboratory to produce bypass fat using acid oil by precipitation and fusion methods. The degree of saponification by both of these methods was above 80 percent. Where heating facilities are not available, precipitation method could be used, otherwise, fusion method of bypass fat production is found to be more convenient, especially for commercial scale operations as handling of large volume of solutions is eliminated. Bypass fat thus produced was tested in vitro for rumen fermentation. Incorporation of acid oil in the incubation medium reduced TVFA conc. from 127.06 to 124.09 mM/l SRL and increased ammonia-N levels from 210.50 to 223 mg/l SRL indicating that the microbial activity was affected on incorporation of acid oil in the incubation medium. However, incorporation of bypass fat in the incubation medium did not significantly affect TVFA conc. as well as ammonia-N levels. In another experiment, nine rumen fistulated sheep in three groups of three each were fed bypass fat at two different levels. Dry matter disappearance in 24 h from the nylon bags suspended in the rumen of animals under different groups was found to be $47.74{\pm}1.10$, $47.55{\pm}0.21$ and $50.74{\pm}1.11$ in group I (control), group II (fed bypass fat 50 g/day) and group III (fed bypass fat 100 g/day), respectively. These studies indicated that it is possible to produce bypass fat from acid oils, a by-product of oil refining process, and its feeding did not affect rumen fermentation.

Triphenylamine coupled chitosan with high buffering capacity and low viscosity for enhanced transfection in mammalian cells, in vitro and in vivo

Garg, Pankaj,Kumar, Santosh,Pandey, Shambhavi,Seonwoo, Hoon,Choung, Pill-Hoon,Koh, Joonseok,Chung, Jong Hoon The Royal Society of Chemistry 2013 Journal of Materials Chemistry B Vol.1 No.44

Giant Duplication Cyst Presenting as a Discharging Umbilicus

Garg, Ravi Kumar,Bawa, Monika,Rao, Katragadda Lakshmi Narasimha The Korean Society of Pediatric Gastroenterology 2017 Pediatric gastroenterology, hepatology & nutrition Vol.20 No.3

Alimentary tract duplication cysts are rare congenital anomalies, most commonly located in the ileum, but may present anywhere from mouth to anus.Clinically, they may be asymptomatic, incidentally diagnosed or may present with obstruction, volvulus, intussusception or gastrointestinal bleed. Here we report a case of a one year old male child presenting in gasping state and shock. Despite the initial strong suspicion of Meckel's diverticulum and tubercular abdomen, the final diagnosis remained elusive till exploratory laparotomy was performed which revealed a duplication cyst of ileum with perforation into the umbilicus. Duplication cyst should always be kept as a differential diagnosis so that early intervention can help in better management.

Role of Bypass Protein in Feeding Ruminants on Crop Residue Based Diet - Review -

Garg, Manget Ram Asian Australasian Association of Animal Productio 1998 Animal Bioscience Vol.11 No.2

Measurement of DCP is considered inadequate and unsatisfactory means of assessing the protein value of the diet as no distinction is made between the digestion in ferestomach and in the small intestine. Protein meals should be classified on the basis of rumen degradable protein (RDP) and rumen undegradable protein (UDP). Usually, protein meals naturally available with high level of UDP or bypass protein value should be preferred for incorporation in the diet of lactating and growing animals. However, if such resources are non-available or are expensive, protein meals having high degradability can be carefully subjected to heat or formaldehyde treatment to achieve desired level of rumen bypassability. Various studies conducted the world over have revealed that bypass protein feeding to ruminants, especially when animals are fed on crop residue based basal diet, help increasing feed conversion efficiency in growing and lactating ruminants.