Rice Husk Ash와 실리카퓸을 혼입한 초기재령 콘크리트의 내구성능 평가

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

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.

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.

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>

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.

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>

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>

Analysis of Corrosion Resistance Behavior of Inhibitors in Concrete using Electrochemical Techniques

( Ha Won Song ),( Velu Saraswathy ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 METALS AND MATERIALS International Vol.12 No.4

Reinforced concrete is one of the most durable and cost effective construction materials. However, in high chloride environments, it can suffer from corrosion due to chloride induced breakdown of the normal passive layer protecting the reinforcing steel bars inside concrete. One means of protecting embedded steel reinforcement from chloride induced corrosion is the addition of corrosion inhibiting admixtures. In the present investigation, various inhibitors such as sodium nitrite, zinc oxide, mono ethanol amine, diethanolamine, and triethanol amine have been used in concrete in different percentages. Their effectiveness was then studied using various electrochemical techniques such as rapid chloride ion penetration test, open circuit potential measurement, electrochemical impedance measurement, potentiodynamic polarization measurement, and gravimetric weight loss measurement. The results thus obtained indicate that the addition of inhibitors enhances the corrosion resistance properties.

Microstructure Characteristics of Fly Ash Concrete with Rice Husk Ash and Lime Stone Powder

Sang-Hwa Jung,Velu Saraswathy,Subbiah Karthick,Palanivel Kathirvel,Seung-Jun Kwon 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.2

Industrial wastes and recycled materials are being utilized in the construction industry for preserving the environment, saving of materials, and enhancing durability of the construction material. Blending of cement with supplementary cementitious materials like fly ash, rice husk ash, and silica fume makes concrete more durable. The main objective of this study is to make use of the rice husk ash and lime powder (LP) as a replacement of Portland pozzolana cement considering various replacement levels. The engineering and durability performance in concrete with LP were performed through compressive strength and void measurement. The microstructure in the concrete with LP was characterized through XRD, SEM/EDS, and TG/DTA. Optimum replacement ratio for rice husk ash and LP were obtained through pozzolanic reaction based CSH formation.

Strength and Durability Performance of Alkali-Activated Rice Husk Ash Geopolymer Mortar

Kim, Yun Yong,Lee, Byung-Jae,Saraswathy, Velu,Kwon, Seung-Jun Hindawi Publishing Corporation 2014 The Scientific World Journal Vol.2014 No.-

<P>This paper describes the experimental investigation carried out to develop the geopolymer concrete based on alkali-activated rice husk ash (RHA) by sodium hydroxide with sodium silicate. Effect on method of curing and concentration of NaOH on compressive strength as well as the optimum mix proportion of geopolymer mortar was investigated. It is possible to achieve compressive strengths of 31 N/mm<SUP>2</SUP> and 45 N/mm<SUP>2</SUP>, respectively for the 10 M alkali-activated geopolymer mortar after 7 and 28 days of casting when cured for 24 hours at 60°C. Results indicated that the increase in curing period and concentration of alkali activator increased the compressive strength. Durability studies were carried out in acid and sulfate media such as H<SUB>2</SUB>SO<SUB>4</SUB>, HCl, Na<SUB>2</SUB>SO<SUB>4</SUB>, and MgSO<SUB>4</SUB> environments and found that geopolymer concrete showed very less weight loss when compared to steam-cured mortar specimens. In addition, fluorescent optical microscopy and X-ray diffraction (XRD) studies have shown the formation of new peaks and enhanced the polymerization reaction which is responsible for strength development and hence RHA has great potential as a substitute for ordinary Portland cement concrete.</P>