Dr. V.V.L. Kanta Rao, Principal Scientist, Bridges and Structures Division, CSIR-Central Road Research Institute, New Delhi

Deformed carbon steel reinforcement bar is most vulnerable to corrosion. Corrosion of reinforcement results in cracking of concrete and loss of structural capacity. The corrosion of steel reinforcement in concrete structures, including bridges, is caused due to chlorides and atmospheric carbon dioxide. The concretes with high permeability allow easy passage of the chlorides and carbon dioxide into it to reach steel reinforcement. Various methods are available to prevent/delay the on-set of corrosion of reinforcement. This paper discusses the common methods adopted for prevention of corrosion during construction.

Introduction

Cement concrete is a versatile building material and is the second most consumed material in the world, after water. It is made using porland cement, coarse, and fine aggregates, water and one or more admixtures. Concrete is well known for the ease with which it is made, for its ability to be moulded in any form, and its high strength. The microstructure of concrete is such that it has capillary pores to the extent of 28%, which depends upon quality of concrete and the presence of water at the time of mixing of concrete. Concrete made with low w/c ratio is dense with lower amount of pores. These pores are created due to evaporation of excess free water during strengthening of concrete mass, and a concrete made with high w/c ratio will have pores inter connected and extend deep inside the mass of concrete from its surface. More are the inter connected pores, greater is the ease with which water can flow through the concrete (i.e. high permeability).

The durability of concrete is defined as its ability to perform satisfactorily in the given exposure conditions, and it is influenced by the pore structure of the concrete. Inadequate durability has been the cause of premature failures of many concrete structures. The concrete undergoes deterioration due to corrosion of steel reinforcement in concrete, sulphate attack, freeze-thaw attack, alkali-silica reaction, etc. Among them, the corrosion of steel in concrete has been identified as most severe types of attack responsible for deterioration of concrete. The corrosion of steel results in increase in its volume by up to 5-7 times and the resulting expansion of steel exerts tensile stresses in concrete upto about 70 MPa (10000 psi) [1] which is much less than the tensile strength of concrete. These disruptive forces cause disintegration of concrete through development of cracks, delamination, and cracking leading to loss of integrity of concrete, reduction in load bearing capacity and service life of the bridges.

The deformed carbon steel is most vulnerable to corrosion compared to plain carbon steel. Before 1970's, plain carbon steel reinforcement bars were used in bridge structures. The use of deformed carbon steel bars have come into use since mid-70's. It is not the intention of the author to recommend the use of plain carbon steel bars as reinforcement, but only to highlight the vulnerability of deformed carbon steel bars to corrosion. A concrete bridge built across River Damodar during mid 60's, using plain carbon steel bars as reinforcement, was tested recently by CSIR-CRRI. No distress exhibited as cracks or spalling was noticed on the bridge due to corrosion. Depth of carbonation (i.e. attack of carbon dioxode) was not significant.

This section of the article is only available for our subscribers. Please click here to subscribe to a subscription plan to view this part of the article.

Click Here
To Know More or to Contact the Manufacturer
Please let us know your name.
Invalid Input
Please let us know your Designation.
Please let us know your Contact Number.
Please let us know your email address.
Please brief your query.
Our other Value-Added Services:

To receive updates through e-mail on Products, New Technologies & Equipment, please select the Product Category(s) you are interested in and click 'Submit'. This will help you save time plus you will get the best price quotations from many manufacturers, which you can then evaluate and negotiate.

Invalid Input
Invalid Input
Invalid Input
The former Prime Minister of India Shri H D Devagowda laid the foundation stone of the Bogibeel Bridge on January 22, 1997 at Kulajan (Assam). After 5 years of laying of the foundation, on April 22, 2002 the Prime Minister of India Shri Atal Behari Vajpayee

Read more ...

As part of Northeast Policy, the Ministry of Railways took up the project of providing rail connectivity to Imphal in Manipur state. As per the detailed survey, the rail alignment takes off from existing Jiribam

Read more ...

Brahmaputra is one of the longest river in Asia with a total length of 2880 km & out of which 920km (approx.) lie in India. The New Brahmaputra Bridge @ Tezpur is one of the most challenging one, in the attempt to bridge

Read more ...

The road and railway crossing across the Brahmaputra on National Highway-52B is located at Bogibeel, about 17km downstream of Dibrugarh in Assam. The location is an area of high intensity rainfall (the annual rainfall ranges

Read more ...

The world has progressed beyond imaginations. Similar to the field of IT, Civil Engineering has also taken several steps forward to bring out innovative technologies to meet challenges of this world’s aspirations. Going forward from

Read more ...

The bridge lies in the state of Assam, but this location is usually referred to as upper Assam as it is far away from Guwahati and bordering China. The nearest airport is Dibrugarh. Then there is a drive of 65km into the

Read more ...

The Infrastructure Industry is continuously evolving; new roads, elevated corridors, expressways, railways, dedicated corridors, metros, mono-rails are being constructed all the time. They also require constant

Read more ...

The 6.5 feet wide walkway in the Hongyagu Scenic Area in Hebei province hangs 755 feet above the ground, and is the world's longest bridge, which opened in 2017-end. Designed by Tel Aviv architect Haim Dotan

Read more ...

Prestressed Concrete (PSC) structures especially bridges are being largely used all over the world due to their multifarious advantages in terms of structural behaviour, economy as well as aesthetical

Read more ...

Four Span Pipe Bridge
Distressed structures require necessary remedial measures in order to restore their original structural properties like strength and stiffness. Validating the effectiveness of the proposed qualitative remedial

Read more ...

Foot Bridges
Footbridges have a longer history than road or railway bridges. Ancient footbridges comprised of natural materials such as roots of trees, ropes, stones, masonry, and wood. Modern footbridges are built

Read more ...

Thane Creek Bridge
Load testing is done to determine the safe load carrying capacity of structures, determining if specific legal or overweight vehicles can safely cross the structure or needs to be restricted and the level of post

Read more ...

Concrete Road Bridges
Planning, design and construction of bridges and flyovers is very challenging at places with space constraints. There has been rapid development with the availability of high strength steel and concrete

Read more ...

Integral Abutment Bridges
The conventional bridges use expansion joints and bearings to accommodate the thermal movements of the bridge. However, they don't completely eliminate the distress caused because

Read more ...

Bridge Restoration
The use and advantages of Post Tensioning are very well known in the Civil Engg Industry as it has been in use for the last 40 to 50 years. Post tensioning is one of the best methods to induce stresses in the concrete

Read more ...

Signature Bridge
Wazirabad Bridge or Signature Bridge Project is an initiative of Delhi Government, planned during the Commonwealth Games. It was conceptualized to be a landmark tourist icon that would also speed

Read more ...

Integral Abutment Bridge
An integral bridge may be defined as having no expansion joints or sliding bearings, the deck is continuous across the length of the bridge. Integral bridges are alternatively referred to as integral abutment

Read more ...

Soil Structure Interaction
A type of bridge that is used extensively in road applications in particular is the integral abutment bridge (IAB). The concept of "integral abutment bridge" has recently become a topic of remarkable

Read more ...

Cracks in Ravi Bridge
Before carrying out any testing of the concrete structures using NDT methods, visual inspection of the structure is a must. Visual inspection is not confined to the surface, it also include examination of bearings

Read more ...

×
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.