Critical Chloride Content in Reinforced Concrete: A Review

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)

Corrosion of steel by concrete

Chloride threshold level for corrosion of steel in concrete

Probability, Reliability and Statistical Methods in Engineering Design

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Aramis Or The Love Of Technology

The rate of corrosion of the reinforcing bars is one of the important parameters required to estimate the residual service-life of a reinforced concrete (RC) bridge deck. In the present study, first, the linear polarization resistance technique was used to measure the corrosion rates of plain mild steel and cold twisted deformed (CTD) bar specimens, which were typically used in the older existing bridges. To consider the variability of a corrosion rate, the frequency distributions of the corrosion rates for the two types of bars were determined. Next, a probabilistic approach was adopted for assessing an existing RC girder-and-slab road bridge deck, subjected to corrosion of bars attributable to air-borne chlorides. A computational model was developed using the Monte Carlo simulation method, to assess the reduction in the flexural capacity of a typical girder. It was observed that the reduction in the mean capacity and the dispersion of the capacity with respect to time, were high with the measure...

Evaluation of Corrosion Rates of Reinforcing Bars for Probabilistic Assessment of Existing Road Bridge Girders

This paper investigates the mechanisms of corrosion of seven-wire strands and the reasons for failures in detecting corrosion at early stages. As per ASTM G109 and ACI 222 R-01, a 1-year study on c...

Macrocell corrosion mechanisms of prestressing strands in various concretes

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, practitioners hesitate to adopt CP for repair due to the lack of evidence and limited knowledge on the long-term performance of galvanic anodes in concrete systems. For this, two reinforced concrete panels with and without discrete galvanic anodes were cast with admixed chlorides and exposed to a natural environment for 12 years. Electrochemical measurements, such as depolarized corrosion potentials and corrosion rate of the rebars, and output protection current density of the galvanic anodes were measured. In addition, physico-chemical characteristics such as elemental composition , residual lithium content, pH, pore volume, and pore size distribution in the encapsulating mortar were determined on a 12-year in-service galvanic anode. This paper indicates that the alkali-activated galvanic anodes can protect the steel rebars from corrosion for at least 12 years. Analysis after 12 years showed that the pores in encapsulating mortar were partially filled with zinc corrosion products , resulting in substantial pore blockage surrounding the zinc metal. This led to a reduction in the pH buffer in the vicinity of the zinc metal. Also, characteristics of tie wire-zinc metal interface may affect the long-term performance of galvanic anodes. Based on this study, specifications are proposed to help manufacturers to design durable galvanic anode systems.

Long-term performance of galvanic anodes for the protection of steel reinforced concrete structures

High-performance cementitious grout with fly ash for corrosion protection of post-tensioned concrete structures

Literature has provided a robust evidence on the link between financial inclusion and development. The onus lies on governments on ensuring the diffusion of financial services to the remote corners of the nation. The rapid diffusion, penetration and global reach of Information Communication Technologies (ICT) have assisted and continues to assist this aim of governments to a large extent. Financial management is, for the poor, a fundamental and well-understood part of everyday life. To enable them with better access to needs in life leading to social inclusion, they have to supported by external financial services. In light of this scenario, this paper attempts to understand a project from the Actor Network Theory (ANT) perspective focussing on improving the disbursement of financial services in an emerging economy. Statistics indicate India has the lowest penetration of banks/ATMs per 100,000 population compared to any of the BRICS nation. The Indian Postal department utilising its large Postal Network in the world with 90% penetration in the rural areas leverage this large network for disbursement of financial services to all citizens focussing primarily on rural villages. Bringing banking services closer to citizens through these post offices ensure efficient, accessible and readily available banking network across the nation. Thereby guaranteeing financial inclusion to the rural populations. The paper highlights the dynamics and the network involved in the process of ensuring financial inclusion, followed by addressing the critical success factors and pain points in the development of this project. The study provides an example of an emerging economy utilising the available resources attempt to attain development through efficient banking system.

Radhakrishna G. Pillai

Papers

Evaluation of Corrosion Rates of Reinforcing Bars for Probabilistic Assessment of Existing Road Bridge Girders

Macrocell corrosion mechanisms of prestressing strands in various concretes

Long-term performance of galvanic anodes for the protection of steel reinforced concrete structures

High-performance cementitious grout with fly ash for corrosion protection of post-tensioned concrete structures

India Posts Putting Its Best Leg Forward: A Case On ICT4D