Studies on the Performance of Self Healing of Plastic Cracks Using Natural Fibers in Concrete

Saraswathy, Velu,Kwon, Seung-Jun,Karthick, Subbiah Korean Recycled Construction Resources Institute 2014 한국건설순환자원학회 논문집 Vol.2 No.2

Addition of fibers in cement or cement concrete may be of current interest, but this is not a new idea or concept. Fibers of any material and shape play an important role in improving the strength and deformation characteristics of the cement matrix in which they are incorporated. The new concept and technology reveal that the engineering advantages of adding fibers in concrete may improve the fracture toughness, fatigue resistance, impact resistance, flexural strength, compressive strength, thermal crack resistance, rebound loss, and so on. The magnitude of the improvement depends upon both the amount and the type of fibers used. In this paper, locally available waste fibers such as coir fibers, sisal fibers and polypropylene fibers have incorporated in concrete with varying percentages and l/d ratio and their effect on compressive, split, flexural, bond and impact resistance have been reported.

Stress Corrosion Behavior of Ungrouted Pretensioned Concrete Beams

Saraswathy, Velu,Lee, Han-Seung,Karthick, Subbiah,Kwon, Seung-Jun Hindawi Limited 2018 Advances In Materials Science And Engineering Vol.2018 No.1

<P>Prestressed concrete beams of size 150 × 150 × 1000 mm were designed, and two bonded cold-drawn 7 mm steel wires were stressed at 70% UTS under service conditions before concreting. The beams were cast with M40 grade concrete mix with various percentages of chlorides ranging from 0, 1, 2, and 3% by weight of cement and cured for 28 days. After 28 days, the stretching forces were released, the prestressing steel wire was allowed to regain its original length, the tensile stresses were transformed into a compressive stress in the concrete, and the stress corrosion behavior was assessed. Stress corrosion cracking (SCC) is due to the simultaneous action of stress, corrosive media, and material properties. The stress corrosion behavior of ungrouted pretensioned steel was assessed by using various electrochemical techniques such as electrochemical noise, open-circuit potential measurement, AC impedance, and potentiodynamic polarization measurements. The same experiments were conducted for rebars embedded in the concrete beam with various percentages of chlorides ranging from 0, 1, 2, and 3% by weight of chloride. After 30 days of exposure, the beams were tested for their flexural strength measurements to find out the load-bearing capacity.</P>

Comparative Study of Strength and Corrosion Resistant Properties of Plain and Blended Cement Concrete Types

Saraswathy, Velu,Karthick, Subbiah,Lee, Han Seung,Kwon, Seung-Jun,Yang, Hyun-Min Hindawi Publishing Corporation 2017 Advances In Materials Science And Engineering Vol.2017 No.1

<P>The relative performances of mechanical, permeability, and corrosion resistance properties of different concrete types were compared. Concrete types were made from ordinary Portland cement (OPC), Portland pozzolana cement (PPC), and Portland slag cement (PSC). Compressive strength test, effective porosity test, coefficient of water absorption, short-term accelerated impressed voltage test, and rapid chloride permeability test (RCPT) were conducted on M30 and M40 grades of concrete designed with OPC, PPC, and PSC cements for 28- and 90-day cured concrete types. Long-term studies such as microcell and electrochemical evaluation were carried out to understand the corrosion behaviour of rebar embedded in different concrete types. Better corrosion resistant properties were observed for PSC concrete by showing a minimum current flow, lowest free chloride contents, and lesser porosity. Besides, PSC concrete has shown less coefficient of water absorption, chloride diffusion coefficient (CDC), and lower corrosion rate and thereby the time taken for initiation of crack extended.</P>

Development and validation of a novel screening instrument to prioritize the orthodontic referral of developing malocclusion in children: The index for interceptive orthodontics referral

Saraswathy Devi Sinniah,Annapurny Venkiteswaran,Najiyatu Nazihah Zakaria 대한치과교정학회 2023 대한치과교정학회지 Vol.53 No.2

Objective: The absence of a guideline to refer to developing malocclusions appropriately, may be a contributing factor to the inadequacy of timely interceptive orthodontics provision. This study aimed to develop and validate a new orthodontic grading and referral index to be used by dental frontliners to prioritize the orthodontic referral of developing malocclusion in children based on its severity. Methods: A cross-sectional study involving clinical assessment with 413 schoolchildren aged between 8.1 and 11.9 years was conducted in 2018. All the presenting malocclusion was listed and graded based on a few dental guidelines to produce the draft index. The validity and reliability of the draft index were tested using twenty study models. Face and content validation was carried out using the content validation index and Modified Kappa Statistics. Results: Fourteen dental and occlusal anomalies were identified as components of malocclusion and three grades of referral (monitor, standard, urgent) were included in the final index. The scale-level content validity index average value of 0.86 and 0.87 was obtained for content and face validation, respectively. There was moderate to excellent agreement in the Modified Kappa Statistics for both validations. Excellent inter- and intra-assessor agreement was obtained. The new index displayed valid and reliable scores. Conclusions: The Index for Interceptive Orthodontics Referral was developed and validated for the dental frontliners to identify and prioritize the developing malocclusion in children based on its severity and refer for orthodontic consultation to increase the possibility for interceptive orthodontics.

Extraction of chloride from chloride contaminated concrete through electrochemical method using different anodes

Saraswathy, Velu,Lee, Han-Seung,Karthick, Subbiah,Kwon, Seung-Jun Elsevier 2018 Construction and Building Materials Vol.158 No.-

<P><B>Abstract</B></P> <P>Electrochemical chloride removal is one of the superior healing methods for chloride affected reinforced (RC) concrete structures. In the present study, the effect of electrochemical chloride removal (ECR) of chloride contaminated concrete consisting of embedded rebar in corroded condition was assessed by measuring the corrosion rate and rebar potential after the ECR treatment at a current density of 0.5, 1.0 and 2.0 mA/m<SUP>2</SUP> and by using three types of anodes namely, TiSA, SSA and, CCPA. Here, ‘current ON’ (ON<SUB>C</SUB>) and ‘current OFF’ (OFF<SUB>C</SUB>) method was adopted to obtain an efficient and uniform ECR throughout the specimen. From the results, it is found that the increase in current density (1.0 and 2.0 A/m<SUP>2</SUP>) increases the chloride removal efficiency. However, the corrosion rate of the rebar was increased at higher current densities and some damage on the CCPA anode material was noticed due to the hydrogen gas evolution in the rebar. It is found that the CCPA is more stable and the chloride removal efficiency was improved at 0.5 A/m<SUP>2</SUP> current density and hence it is suitable for long-time application of ECR process under ON<SUB>C</SUB> and OFF<SUB>C</SUB> method. This approach allows the easier passage of chloride ions from the cathode to the anode and the current OFF<SUB>C</SUB> period allows the system to re-establish the equilibrium between the anode and cathode. From this study, it was found that the ‘‘ON<SUB>C</SUB> and OFF<SUB>C</SUB> method’’ increases the chloride removal efficiency and thereby preventing the rebar from corrosion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ECR process development by using three different anodes and current densities. </LI> <LI> ECR process was carried out under laboratory and field exposed concretes. </LI> <LI> The CCPA is stable at 0.5 A/m<SUP>2</SUP> and suitable for long-time application. </LI> <LI> The higher current density is not suitable for continuous ECR process in all anodes. </LI> <LI> ON<SUB>C</SUB> and OFF<SUB>C</SUB> method increases the chloride removal efficiency. </LI> </UL> </P>

Durability Enhancement in Nano-Silica Admixed Reinforced Mortar

Saraswathy, Velu,Karthick, Subbiah,Kwon, Seung-Jun Korean Recycled Construction Resources Institute 2014 한국건설순환자원학회 논문집 Vol.2 No.4

Recently nano-materials are gaining more importance in the construction industry due to its enhanced energy efficiency, durability, economy, and sustainability. Nano-silica addition to cement based materials can control the degradation of the fundamental calcium-silicate-hydrate reaction of concrete caused by calcium leaching in water as well as block water penetration and therefore lead to improvements in durability. In this paper, the influence of synthesized nano silica from locally available rice husk on the mechanical properties and corrosion resistant properties of OPC (Ordinary Portland Cement) has been studied by conducting various experimental investigations. Micro structural properties have been assessed by conducting Scanning Electron Microscopy, Thermo gravimetry and Differential Thermal Analysis, X-Ray Diffraction analysis, and FTIR studies. The experimental results revealed that NS reacted with calcium hydroxide crystals in the cement paste and produces Calcium Silicate Hydrate gel which enhanced the strength and acts as a filler which filled the nano pores present in concrete. Hence the strength and corrosion resistant properties were enhanced than the control.

Improved Durability Performances in Cement Mortar with Rice Husk Ash

Saraswathy, Velu,Karthick, Subbiah,Kwon, Seung-Jun Korean Recycled Construction Resources Institute 2014 한국건설순환자원학회 논문집 Vol.2 No.1

Currently many researches have been performed for enhancing durability of concrete. Rice husk ash has several advantages like early strength of concrete and dense pore structure. A calcium silicate hydrate (CSH) gel around the cement particles due to pozzolanic reaction of rice husk can increase the strength of concrete against cracking. Very limitedly a systematic and detailed investigation on the corrosion performance of rice husk ash and silica fume blended concrete is performed. A realistic approach has been made through compressive strength, bond strength, and split tensile strength etc. Corrosion performance was also evaluated rapid chloride ion penetration test (RCPT) and impressed voltage test, and the results were discussed in the paper.

Rice Husk Ash와 실리카퓸을 혼입한 초기재령 콘크리트의 내구성능 평가

Velu Saraswathy,권성준(Seung-Jun Kwon) 한국콘크리트학회 2015 콘크리트학회논문집 Vol.27 No.4

Evaluation of Composite Cements using Cyclic Polarization Techniques

V. Saraswathy,S. Muralidharan,L. Balamurugan,P. Kathirvel,A. S. S. Sekar 대한토목학회 2011 KSCE JOURNAL OF CIVIL ENGINEERING Vol.15 No.8

Slag Cement (PSC) extracts in the presence and absence of nitrite inhibitor were studied by cyclic polarization technique. Studies also carried out in composite (binary and ternary) cement extracts. The re-passivation potential (Erep) is an important parameter to characterize the corrosion resistant property of cements and the efficiency of inhibitor. Blended cements (PPC and PSC) have higher tolerable limit of chloride than OPC. Binary cements increase the tolerable limit of chloride than individual cements. The passivity of steel maintained by ternary cement was found to be less than 45000 ppm of chloride along with 5000 ppm of nitrite (pitting occurred at 45000 ppm). This chloride level is more than that of chlorides in natural sea water (35000 ppm). Hence the use of composite cement especially in marine atmosphere increases the corrosion resistance of steel in concrete.

Wound Healing Activity of the Chloroform Extract of Plumbago rosea Linn. and Plumbagin

A. Saraswathy,R.V. Pradeep Chandran,B. Murali Manohar,S.Vairamuthu 한국생약학회 2006 Natural Product Sciences Vol.12 No.1

wound healing activity of plumbagin and the chloroform extract of Plumbago rosea Linn. (Yoot),incorporated into ointments with yellow soft paraffin, have been investigated on rats. Wound healing activity wasstudied using excision and incision wound models in rats following topical application. Both plumbagin and thePlumbago rosea root extract produced a significant response in both of the wound models studied. The woundPlumbago rosea root extract (0.5%),as against in 22 days in the case of control animals. The results were also comparable to those of a standard drug,framycetin sulphate cream (1% w/w) in terms of wound contracting ability, wound closure time, tensile strengthof wound and regeneration of tissues at the wound site. Histological studies revealed evidences for the healingprocess by formation of fibrovascular tissue, epithelization and increased collagenization when compared tocontrol.Keywordswound healing activity, Plumbago rosea, plumbagin, Plumbaginaceae