Radhakrishna Pillai

Radhakrishna Pillai
Indian Institute of Technology Madras | IIT Madras · Department of Civil Engineering

Doctor of Philosophy

About

159
Publications
123,238
Reads
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1,154
Citations
Introduction
Additional affiliations
July 2017 - present
Indian Institute of Technology Madras
Position
  • Professor (Associate)
September 2010 - July 2017
Indian Institute of Technology Madras
Position
  • Professor (Assistant)
September 2010 - July 2017
Indian Institute of Technology Madras
Position
  • Professor (Assistant)
Education
January 2004 - May 2009
Texas A&M University
Field of study
  • Civil Engineering

Publications

Publications (159)
Article
Concretes with fly ash, slag, limestone calcined clay, etc. exhibiting high resistivity are being used to enhance the chloride resistance of structures – to achieve durability. Prior to use, the engineers need to determine the chloride threshold (Clth) of such highly resistive steel cementitious (S-C) systems (a key parameter to estimate service li...
Article
Full-text available
Currently, highway/railway bridges are designed for the service life of more than 100 years. In such reinforced concrete structures, fusion-bonded-epoxy (FBE) coated steel rebars are being used in anticipation of delayed initiation of reinforcement corrosion. However, the FBE steel rebars get exposed to sunlight/ultraviolet rays during prolonged st...
Article
Full-text available
Read articles on corrosion and its control in concrete structures (C3S) with sub-themes on corrosion assessment, materials for corrosion resistance, service life estimation, and cathodic protection in the November edition of ICJ. Read more: https://icjonline.com/explore_journals/2020/11/
Article
Full-text available
This paper evaluates the suitability of various techniques such as half-cell potential, macrocell corrosion, linear polarization resistance, and electrochemical impedance spectroscopy (EIS) to detect corrosion initiation of fusion-bonded-epoxy (FBE) coated steel rebars in concrete. It was found that EIS is the best technique for this purpose. Then,...
Article
Full-text available
Seven-wire strands in pretensioned concrete (PTC) structures can undergo chloride-induced localized corrosion. The corrosion products occupy the space between the wires of the strands and do not exert expansive stresses onto the surrounding concrete. Hence, propagation of such corrosion cannot be identified/ detected on time using visual observatio...
Article
Full-text available
This paper investigates the corrosion and bond characteristics of steel reinforcement with Cement-Polymer-Composite (CPC) coating, which is widely used worldwide to prolong the initiation of corrosion. CPC coating is supposed to be applied on sandblasted orcleaned surface to exploit its full potential. However, CPC coating is generally applied on t...
Article
Full-text available
Corrosion of strands can cause brittle failure of prestressed concrete bridge girders. The present study experimentally investigated the effect of chloride-induced corrosion on the tensile behaviour of 7-wire strands commonly used in prestressed concrete structures. Five prism specimens with embedded strands were subjected to impressed current corr...
Patent
The principal object of the present invention is to develop an efficient short-term test method for evaluating the performance and life of galvanic anodes used for cathodic protection of concrete structures from corrosion. The present invention helps in identifying a high-performance, durable, and long-lasting galvanic anode component.
Chapter
In the past two decades, developing world is witnessing a construction boom. Many infrastructural systems such as highway/railway bridges, high-rise buildings, and power plants have been constructed in regions with significant chloride and/or carbonation exposure. These structures are expected to be serviceable for more than 100 years. However, man...
Article
Supplementary cementitious materials (SCMs) can be used in concrete to enhance sustainability and reduce the concrete industry's carbon footprint. However, some negative perceptions about their long-term carbonation resistance are obstacles for large-scale implementation of such concretes. This study evaluated the carbonation resistance of 34 concr...
Article
Full-text available
Corrosion assessment of reinforced concrete (RC) structures with fusion-bonded-epoxy (FBE) coated steel rebars is a challenge because the common inspection methods and data cannot be applied or interpreted in the same way as that for the systems with uncoated rebars. If corrosion detection tools based on techniques such as half-cell potential (HCP)...
Article
Full-text available
This paper aims to adjust the model parameters of the B4 and B4s models using newly collected laboratory data for blended cement concrete systems of strength grades 25 MPa and 65 MPa. Based on the data, regression analysis for the B4s model has been performed to capture the shrinkage response at later ages better. Also, suitable adjustment of the m...
Article
Full-text available
Use of supplementary cementitious materials (SCMs) has substantially increased in the construction industry in recent years. Long-term data on the effect of different SCMs on shrinkage and creep are scarce. Also, the appropriate prediction of shrinkage is important to ensure that the design can address the structural requirements when blended concr...
Article
Full-text available
The three mechanisms governing the strand-concrete (S-C) bond in pretensioned concrete (PTC) systems are: (i) adhesion, (ii) mechanical interlock, and (iii) friction. These mechanisms can be influenced by various parameters like the compressive strength of concrete (fc), applied prestress (fps), and embedment length of the strand (le). The existing...
Preprint
Currently, many supplementary cementitious materials are being used along with cement to reduce the CO 2 emissions. These cementitious systems exhibit very high resistivity due to pozzolanic reactions and the traditional test methods are inadequate to assess their durability performance related to corrosion, especially chloride threshold (Cl th). T...
Article
Currently, many supplementary cementitious materials are being used along with cement to reduce the CO2 emissions. These cementitious systems exhibit very high resistivity due to pozzolanic reactions and the traditional test methods are inadequate to assess their durability performance related to corrosion, especially chloride threshold (Clth). Thi...
Article
Full-text available
Corrosion is one of the major deterioration mechanisms of reinforced concrete structures. The conventional patch repair without addressing the root cause of the corrosion can lead to repeated repairs. Therefore, a form of cathodic protection (CP) using galvanic anodes is a viable electrochemical technique to mitigate corrosion. However, practitione...
Article
Full-text available
Cold-drawn, high strength, prestressing (PS) steel strands are widely used in pretensioned concrete (PTC) structures. This paper discusses the stress corrosion cracking (SCC) of PS steel embedded in cement mortar and gradually exposed to chlorides. Various stages of the passive to active (P-to-A) transition, which marks the onset of SCC, were inves...
Article
Full-text available
Read articles on corrosion and its control in concrete structures (C3S) focussing on service life design approaches for new structures, evaluation of various techniques for delaying corrosion, and cathodic protection for repair of existing structures. Read more at https://icjonline.com/explore_journals/2021/04/
Article
In order to provide corrosion protection of tendons in post-tensioned (PT) concrete systems, the congested interstitial spaces between the strands and duct are ideally to be filled with cementitious grouts. However, many currently used grouts do not have the desired fluidity and resistance to segregation – leading to formation of voids, frothy grou...
Article
Full-text available
This paper presents a market study indicating that Patch Repair without galvanic anodes (PR strategy) can lead to continued corrosion (due to the halo effect and residual chloride effect) and another major repair in about five years. Repeated patch repairs can lead to continued corrosion and eventual replacement of structures and huge life cycle co...
Article
Full-text available
Fly ash and limestone calcined clay cement (LC3) are being used/introduced in concrete to enhance chloride resistance. In this study, sixty specimens (with steel in three concrete systems, namely OPC, fly ash, and LC3 with surface resistivity of ≈10, ≈25, and ≈200 kΩ.cm, respectively) were subjected to impressed corrosion and the results were compa...
Article
Full-text available
The urge to reduce the carbon footprints from cement production warrants the development of more sustainable approaches in the construction industry. Towards this, the long term corrosion resistance of the embedded steel rebar in a novel ternary-blended reinforced concrete system with 56 wt% Ordinary Portland cement (OPC), 40 wt% fly ash, 2 wt% nan...
Article
Full-text available
Fusion-bonded-epoxy (FBE) coated steel rebars have been used in many concrete structures in anticipation of better corrosion resistance. However, due to premature corrosion observed, many FBE coated rebars are banned in many parts of the world. On the other hand, such rebars with damaged coating are still used widely in some other parts of the worl...
Poster
Full-text available
A mechanism for chloride-induced depassivation of pretensioned concrete systems is proposed based on the evolution of the electrochemical response with exposure to chlorides, and micrographic evidences.
Presentation
Delays associated with corrosion detection by visual inspection can lead to significant structural safety issues. As a solution, a methodology to obtain input parameters (especially the chloride threshold of prestressed steel) and carry out routine residual life estimation, was presented.
Article
Full-text available
About a decade of research carried out at IIT Madras on cementitious systems has shown that the partial replacement of portland cement with supplementary cementitious materials (SCMs) has benefits as well as limitations. The SCMs do not adversely affect the long-term compressive strength and drying shrinkage of concretes, though there may be some c...
Article
Full-text available
Quality Microstructure Testing of TMT / QST steel reinforcement in concrete
Article
Full-text available
Posttensioned (PT) bridges are used on major thoroughfares because they are economical structures for traversing long spans. Special inspections of these bridges have revealed corrosion of the strands at void locations in the tendons. The integrity of these strands has significant influence on the safety of these bridges. Inspections indicate that...
Article
Full-text available
The presence of air voids, moisture, and chlorides inside tendon systems on segmental posttensioned ͑PT͒ bridges has been cited as a reason for the early age corrosion and failure of strands in these bridges. This paper develops probabilistic models to predict the time-variant tension capacity of PT strands exposed to wet-dry conditions. A total of...
Article
Full-text available
To evaluate the influence of the steel reinforcement surface condition on the corrosion performance, the critical chloride threshold values of five uncoated steel reinforcement types (ASTM A 706, ASTM A 615, microcomposite, stainless steel 304, and stainless steel [SS] 316LN) with as-received and polished surface conditions were quantitatively dete...
Article
Full-text available
The presence of air voids, moisture, and chlorides inside tendons or ducts was cited as a reason for the early age strand corrosion and failure in the Mid-bay, Sunshine Skyway, and Niles Channel posttensioned ͑PT͒ bridges in Florida, United States. Although rare, these incidents call for frequent inspection and structural reliability assessment of...
Article
Full-text available
A 12-month long strand corrosion test program with 298 specimens was conducted to identify and quantify parameters influencing corrosion and tension capacity of strands in post-tensioned bridges. The parameters investigated were grout class, moisture content, chloride concentration, void type, and stress level. The test specimens were 41 in. (1041...
Article
Full-text available
To evaluate the service-life and life-cycle costs of reinforced concrete structures susceptible to corrosion, quantitative measures of key material properties and parameters must be known. For chloride-induced corrosion, key material properties include the transport rate of the chloride ions (such as diffusivity and sorptivity) in the cementitious...
Article
Full-text available
Test methods to evaluate the corrosion performance of reinforcing steel have been typically developed to evaluate the corrosion rate of conventional plain carbon steel in cementitious materials. Although the corrosion rate is a necessary parameter for predicting the service life of reinforced concrete structures, these data alone are not sufficient...
Article
Full-text available
Nowadays, Cement-Polymer-Composites are widely used to coat steel rebars to delay the initiation of corrosion in reinforced concrete (RC) structures. However, Cement-Polymer-Composite (CPC) coating is sometimes inadequately applied on rusted steel and can lead to premature under film/crevice corrosion. This paper investigates the effect of such ina...
Article
Full-text available
This paper presents a summary of the major findings from the studies conducted at IIT Madras on Limestone Calcined Clay Cement (LC3), in comparison with plain portland cement and fly ash-based binder. The study attempts to delineate the chemical and physical effects of binder components in LC3 on hydration and hardening, property development, binde...
Conference Paper
Full-text available
In the light of the increasing demand for cement in construction and dwindling reserves of cement-grade limestone, the blend of ground limestone and lower grade calcined clay has emerged as a potential candidate for large volume cement replacement. Studies of such ternary blended systems in paste and concrete reveal very interesting physical and ch...
Article
Full-text available
This paper presents an experimental study on Lt in pre-tensioned concrete (PTC) members made of four values of compressive strength of concrete. Also, it presents a comparison between the formulations of transmission length (Lt) given in various codes and other literature. A test specimen consisted of a concrete prism (100 × 100 × 2000) mm with a p...
Article
Full-text available
The article [Title], written by [AuthorNames], was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 3 December 2018 without open access.
Article
This paper describes a unique international inter-laboratory study on the carbonation resistance of concrete prepared with different supplementary cementing materials. Concrete specimens – from 45 different concrete mixtures – prepared centrally in Lafarge Centre de Recherche (France)were shipped in a sealed condition to 4 other academia research l...
Article
The steel–concrete interface (SCI) is known to influence corrosion of steel in concrete. However, due to the numerous factors affecting the SCI—including steel properties, concrete properties, execution, and exposure conditions—it remains unclear which factors have the most dominant impact on the susceptibility of reinforced concrete to corrosion....
Article
Full-text available
Carbonation induced corrosion of the embedded steel reinforcement is a major deterioration mechanism of reinforced concrete structures, mainly in inland/ highway environments of tropical countries. Carbonation leads to uniform reduction in the cross sectional area of steel reinforcement. In general, Supplementary Cementitious Materials (SCMs) can i...
Article
This paper presents data on the chloride diffusion coefficient (Dcl), ageing coefficient (m) and chloride threshold (Clth) related to seven concretes (four M35 and three M50) with OPC, OPC+PFA (pulverized fuel ash) and limestone-calcined clay cement (LC3). Using these, the service lives of a typical bridge pier and girder with the PFA and LC3 concr...
Article
Full-text available
This paper presents the evolution of compressive strength and the modulus of elasticity of concretes with binary and ternary blends of ordinary Portland cement, fly ash and ground granulated blast-furnace slag (GGBS or slag). The study involved 54 concrete mixes with water–binder ratio (w/b) varying from 0.50 to 0.65 and the total binder content va...
Conference Paper
Full-text available
Various properties of limestone calcined clay cement (LC3) as a binder and those of concretes made with LC3 were assessed during the last four years at IIT Madras to understand its potential as an alternative mainstream cement. LC3 from two major industry-scale productions was used in the evaluation, and the major findings from the research are sum...
Conference Paper
NACE impact report (2016) states that nearly 50% of reinforced concrete (RC) structures experience major repair in about 10 years. The existing approach of conventional patch repair does not usually address the root cause and may not be durable – resulting in re-repairs in short period (say, 5 to 10 years) and substantial economic loss. Clients and...
Chapter
Full-text available
This paper illustrates the effect of chloride-induced corrosion in the flexural capacity of a pretensioned concrete girder in an existing girder-and-slab deck bridge. The numerical study of the time-wise variation of the flexural capacity is based on a proposed model for the loss of cross-sectional area of the prestressing strands. It was observed...
Chapter
Full-text available
Prestressed concrete technology has revolutionized the infrastructure growth in many countries, especially that of the bridge sector. The bond between prestressed strand and concrete is very important for achieving good structural performance. However, some of the codal provisions have not given enough consideration to the bond strength of pretensi...
Chapter
The Rashtrapati Bhavan, the official residence of the President of India, is a Grade-I heritage structure. The reinforced concrete cantilever sunshades in this building are at a height of about 20 m above ground and span about two-kilometer along the perimeter of the building. In the late 1990s, some sunshades experienced corrosion and were repaire...
Conference Paper
Developing world is building a lot of reinforced concrete (RC) structures. Many of these RC structures are exposed to marine environment. Therefore, chloride-induced corrosion is one of the main deterioration mechanisms for RC structures. Chloride diffusion coefficient (Dcl) is one of the important parameters affecting the estimation of service lif...
Article
A framework is proposed, along with two objective indices, for the selection of concrete mixture proportions based on sustainability criteria. The indices combine energy demand and long-term strength as energy intensity, and carbon emissions and durability parameters as A-indices, which represent the apathy toward these essential features of sustai...
Conference Paper
Grouted, post-tensioned (PT) systems are widely used in long-span segmental bridges, high rise buildings, nuclear vaults, silos etc. To achieve the corrosion-free target service life of 100+ years, the interstitial spaces between the strands and ducts of these PT systems are supposed to be filled with cementitious grouts. However, the use of poor q...