Subbiah Karthick

Effect of different alkali salt additions on concrete durability property

Abstract Friedel’s salt (FS) is a versatile material and has several advantages in constructional and metallurgical sectors. In this paper, FS is formed in situ in concrete. The addition of Al2O3 (5% by weight of cement) was maintained constant and the formation of FS was proceed through the various ranges of NaCl, KCl and CaCl2. Among them, CaCl2 addition was found effective in the large formation of FS in concrete. The influence of FS on the mechanical, permeability and corrosion resistance properties of concrete was studied by electrochemical techniques. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron micrographs were used to characterize the formation of FS in concrete.

Standardization, Calibration, and Evaluation of Tantalum-Nano rGO-SnO2 Composite as a Possible Candidate Material in Humidity Sensors

The present study focuses the development and the evaluation of humidity sensors based on reduced graphene oxide—tin oxide (rGO-SnO2) nanocomposites, synthesized by a simple redox reaction between GO and SnCl2. The physico-chemical characteristics of the nanocomposites were analyzed by XRD, TEM, FTIR, and Raman spectroscopy. The formation of SnO2 crystal phase was observed through XRD. The SnO2 crystal phase anchoring to the graphene sheet was confirmed through TEM images. For the preparation of the sensors, tantalum substrates were coated with the sensing material. The sensitivity of the fabricated sensor was studied by varying the relative humidity (RH) from 11% to 95% over a period of 30 days. The dependence of the impedance and of the capacitance with RH of the sensor was measured with varying frequency ranging from 1 kHz to 100 Hz. The long-term stability of the sensor was measured at 95% RH over a period of 30 days. The results proved that rGO-SnO2 nanocomposites are an ideal conducting material for humidity sensors due to their high sensitivity, rapid response and recovery times, as well as their good long-term stability.

Corrosion and Leaching Studies in Blended Copper Slag Mortar

The effect of copper slag leaching was evaluated using Atomic Absorption Spectroscopy (AAS) immersed in three aqueous media such as tap water, sea water, and synthetic/artificial rain water. The mechanical and corrosion resistance properties of copper slag admixed concrete was evaluated using compression test and various electrochemical tests, respectively. Sand was totally replaced with copper slag in making the concrete specimens. From the investigations it is observed that the copper slag leaching was found to be very less even after 180 days of exposure in aqueous media. Compressive strength revealed that the addition of copper slag increased the compressive strength of the concrete. Rapid Chloride Penetration Test (RCPT) and other electrochemical tests indicated that copper slag admixed mortar performed equal to the sand mortar in sea water environments.

A state-of-the-art review on the durability of silica fume-blended concrete – a boon to the construction industry

Abstract The development and use of blended cement is growing rapidly in the construction industry mainly due to the consideration of energy, environment, and conservation of resources. Blended cements are produced using any of the supplementary cementitious materials such as silica fume (SF), fly ash, and ground granulated blast furnace slag. The use of SF in concrete may improve the strength and durability of concrete by creating a denser cement matrix compared with conventional concrete, thereby enhancing the service life of concrete structures. In this article, the effect of SF in concrete is reviewed from the point of view of durability. It includes carbonation, resistivity, chloride permeability/diffusivity, sulfate resistance, and corrosion resistance.

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

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.

Improved Durability Performances in Cement Mortar with Rice Husk Ash

*(Received March 11, 2014 / Revised March 24, 2014 / Accepted March 25, 2014)Currently many researches have been performed for enhancing durability of concrete. Rice husk ash has several advantages like e arlystrength of concrete and dense pore structure. A calcium silicate hydrate (CSH) gel around the cement particles due to pozzolan ic reaction of rice husk can increase the strength of concrete against cracking. Very limitedly a systematic and detailed investig ation 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 disc ussedin the paper.Keywords : Durability, Rice husk, Pozzolanic admixture, Silica fume, RCPT* Corresponding author E-mail: jjuni98@hannam.ac.kr

Durability Enhancement in Nano-Silica Admixed Reinforced Mortar

* (Received November 5, 2014 / Revised December 4, 2014 / Accepted December 11, 2014)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 leadto 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 streng th and acts as a filler which filled the nano pores present in concrete. Hence the strength and corrosion resistant properties wer e enhanced than the control.Keywords : Nano silica, Chloride penetration, EIS, SEM, TGA, XRD, FTIR* Corresponding author E-mail: jjuni98@hannam.ac.kr

Investigation on Durability Performance in Early Aged High-Performance Concrete Containing GGBFS and FA

The significance of concrete durability increases since RC (Reinforced Concrete) structures undergo degradation due to aggressive environmental conditions, which affects structural safety and serviceability. Steel corrosion is the major cause for the unexpected failure of RC structures. The main cause for the corrosion initiation is the ingress of chloride ions prevailing in the environment. Hence quantitative evaluation of chloride diffusion becomes very important to obtain a chloride diffusion coefficient and resistance to chloride ion intrusion. In the present investigation, 15 mix proportions with 3 water-to-binder ratios (0.37, 0.42, and 0.47) and 3 replacement ratios (0, 30, and 50%) were prepared for HPC (high-performance concrete) with fly-ash and ground granulated blast furnace slag. Chloride diffusion coefficient was measured under nonstationary condition. In order to evaluate the microstructure characteristics, porosity through MIP was also measured. The results of compressive strength, chloride diffusion, and porosity are compared with electrical charges. This paper deals with the results of the concrete samples exposed for only 2 months, but it is a part of the total test plan for 100 years. From the work, time-dependent diffusion coefficients in HPC and the key parameters for durability design are proposed.

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

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.