Combating Chloride
Concrete

Combating Chloride

The backbone of construction, concrete structures that are durable and can sustain seismic activity are made by reinforcing steel in concrete. For dynamic structures such as flyovers and bridges, reinforcement is a must. Today’s multi-storeyed buildings and malls with straight or curved shapes also require reinforced concrete structures (RCC). However, a key negative is the corrosion of reinforcement.

Steel can be imbedded in concrete in any shape. The steel frame of a structure is first erected and then covered with concrete. However, the presence of this steel can result in corrosion of an RCC structure. So, how do chlorides reach steel in the embedded structure? 

The fact is, concrete does not seal the RCC structure because it is porous so it always retains some moisture. Second, the outer layer of concrete, which is called ‘cover’, is always in contact with moisture and pollutants whose concentration varies from place to place and season to season. For instance, a relatively dry environment like Delhi or Rajasthan will have lower moisture and pollutants compared to a wet environment as in Mumbai and Chennai, which have higher humidity. Further, a highly populated city and industrial city may have a high concentration of pollutants such as carbon dioxide and sulphur dioxide and coastal cities also have chlorides in the atmosphere. All these pollutants enter the porous concrete structure by hitting the cover and then making their way into the steel through the concrete pores. As soon as a minimum concentration of these pollutants reaches the steel-concrete interface, the corrosion begins as in Figure 1.

 About the author: Professor AS Khanna is retired from IIT Bombay and is Chairman, SSPC India.

To read the full story, CLICK HERE.


The backbone of construction, concrete structures that are durable and can sustain seismic activity are made by reinforcing steel in concrete. For dynamic structures such as flyovers and bridges, reinforcement is a must. Today’s multi-storeyed buildings and malls with straight or curved shapes also require reinforced concrete structures (RCC). However, a key negative is the corrosion of reinforcement.Steel can be imbedded in concrete in any shape. The steel frame of a structure is first erected and then covered with concrete. However, the presence of this steel can result in corrosion of an RCC structure. So, how do chlorides reach steel in the embedded structure? The fact is, concrete does not seal the RCC structure because it is porous so it always retains some moisture. Second, the outer layer of concrete, which is called ‘cover’, is always in contact with moisture and pollutants whose concentration varies from place to place and season to season. For instance, a relatively dry environment like Delhi or Rajasthan will have lower moisture and pollutants compared to a wet environment as in Mumbai and Chennai, which have higher humidity. Further, a highly populated city and industrial city may have a high concentration of pollutants such as carbon dioxide and sulphur dioxide and coastal cities also have chlorides in the atmosphere. All these pollutants enter the porous concrete structure by hitting the cover and then making their way into the steel through the concrete pores. As soon as a minimum concentration of these pollutants reaches the steel-concrete interface, the corrosion begins as in Figure 1. About the author: Professor AS Khanna is retired from IIT Bombay and is Chairman, SSPC India.To read the full story, CLICK HERE.

Next Story
Infrastructure Energy

KEC Secures Rs 10, 380 Mn Substation Order in Saudi Arabia

KEC International Ltd., a global infrastructure EPC major, and an RPG Group company, has secured a new order worth Rs 10,380 million for the Design, Supply and Installation of a 380 kV GIS Substation in Saudi Arabia.Vimal Kejriwal, MD & CEO, KEC International Ltd., commented, “We are delighted with the successive order wins in our T&D business. In a landmark achievement, we have secured our largest ever substation order. This prestigious order in the Middle East has widened our portfolio and strengthened our presence in the region. With this strategic win, our year-to-date or..

Next Story
Infrastructure Urban

Central Bank of India executes first fully digital SCF deal on PSB Xchange

In a major advancement for India’s banking sector, Central Bank of India (CBI) has successfully completed the country’s first fully digital supply chain finance (SCF) transaction on PSB Xchange—a unified multi-lender platform launched by PSB Alliance. PSB Xchange is designed to connect public and private sector banks, NBFCs, and fintechs with corporates and their channel partners to facilitate supply chain finance and small business loans. The transaction marks the first time a fintech-originated corporate lead has been seamlessly processed through the PSB Xchange ecosystem. The lead fl..

Next Story
Infrastructure Energy

Atlanta Electricals secures Rs 1,835 Mn transformer order from BNC Power

Atlanta Electricals Limited (“Atlanta”) has secured an order worth Rs 1,835 million from BNC Power Projects Ltd for the supply of extra high voltage (EHV) transformers and a bus reactor for its Pugal site. The contract includes a mix of 315 MVA, 400 KV and 100 MVA, 132 KV transformers along with a 400 KV bus reactor. The project scope encompasses design, manufacturing, testing, and supply to the project site. Deliveries will be sequenced following engineering and drawing approvals, offering multi-quarter execution visibility and ensuring a steady production run-rate. The order will be ex..

Advertisement

Subscribe to Our Newsletter

Get daily newsletters around different themes from Construction world.

STAY CONNECTED

Advertisement

Advertisement

Advertisement

Talk to us?