Radhakrishna G. Pillai

Bio: Radhakrishna G. Pillai is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Corrosion & Cementitious. The author has an hindex of 13, co-authored 58 publications receiving 688 citations. Previous affiliations of Radhakrishna G. Pillai include Texas A&M University & Indian Institutes of Technology.

Compressive Strength and Elastic Modulus of Concretes with Fly Ash and Slag

Abstract: 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 varying from 280 to 340 kg/m3. The influence of w/b, type of binder and exposure period (or age) have been assessed. It is seen that the incorporation of slag contributes to both short- and long-term strength, whereas fly ash requires comparatively longer time to contribute to the compressive strength. The relationship between compressive strength and age and between the modulus of elasticity and compressive strength has been discussed.

A short-term test method to determine the chloride threshold of steel–cementitious systems with corrosion inhibiting admixtures

Abstract: Now-a-days, multiple types of corrosion inhibiting admixtures (CIAs) are being used to enhance the chloride threshold (Clth) of steel–cementitious systems. However, due to the application of external potential to drive chlorides, some existing short-term test methods are not suitable to assess the Clth of S–C systems with CIAs containing anions. This paper presents the development of a Modified Accelerated Chloride Threshold (mACT) test to determine the Clth for S–C systems with CIAs. The test specimens consisted of a mortar cylinder with an embedded steel piece and electrodes forming a 3-electrode corrosion cell. The specimens were exposed to chloride solution and the linear polarization resistance tests were conducted every 3.5 days. The corrosion initiation was detected using statistical analysis of the repeated R p measurements. After corrosion initiation, the chloride content in mortar adjacent to the embedded steel piece was determined and defined as Clth. The time required to complete mACT test for an S–C system with CIAs is about 120 days. The Clth of eight specimens each with S–C system containing (i) without inhibitor, (ii) anodic inhibitor [calcium nitrite] and (iii) bipolar inhibitor [both calcium nitrite and amino alcohol] were determined. Both anodic and bipolar CIAs showed enhanced corrosion resistance. Also, the bipolar inhibitor performed better than anodic inhibitor. It was concluded that the use of CIAs could significantly delay the initiation of chloride-induced corrosion. The mACT test can be used to determine the Clth and estimate the service life during the planning and design stages of a project and help select durable materials.

Use of supplementary cementitious materials (SCMs) in reinforced concrete systems – Benefits and limitations

Abstract: 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 compromise in workability and the resistance against plastic shrinkage cracking. Through the assessment of the chloride ingress rate in concrete and chloride threshold of steel, it is evident that the use of SCMs could significantly enhance the service life under chloride attack, though there is a reduction of the carbonation resistance. More importantly, SCMs can lead to significant reduction of the carbon footprint of concrete, and hence, are essential to achieve sustainability.

Effect of Sunlight/Ultraviolet Exposure on the Corrosion of Fusion-Bonded Epoxy (FBE) Coated Steel Rebars in Concrete

Abstract: Currently, highway/railway bridges are designed for the service life of more than 100 y In such reinforced concrete structures, fusion-bonded epoxy (FBE) coated steel rebars are being used in anti

Corrosion of steel by concrete

Abstract: The author details the reactions of various concretes on steel reinforcement. Although portland cements, slag cements and high alumina cements are all hydraulic binders, each possess special properties which are examined. The discussion of causes and methods of preventing the corrosion of steel reinforcement covers such aspects as galvanised steel reinforcement, effects of concrete composition, corrosion of steel reinforcments in concrete and prestressed reinforcement. It is concluded that the most significant influences on the corrosion of prestressing wire in concrete are: the presence of chloride; the presence of nitrates; the composition of the concrete; the degree of carbonation of the concrete; concrete compaction and, chlorides and sulphates should be used as far as possible when steel is embedded. (TRRL)

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