+
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 Urban

Naidu Seeks Rs 563 Crore For AP Sports Infrastructure

Andhra Pradesh Chief Minister N Chandrababu Naidu has sought Rs 563 crore from the Centre to boost sports infrastructure in the state, including Rs 538 crore for stadium development and Rs 25 crore to host the Khelo India Martial Arts Games 2025. Naidu made the request during a meeting with Union Youth Services and Sports Minister Mansukh Mandaviya in New Delhi on Wednesday.The CM urged early completion of Khelo India infrastructure projects in Tirupati, Rajahmundry, Kakinada, and Narasaraopeta, and called for an international-standard badminton training centre and a national aquatic sports hu..

Next Story
Infrastructure Transport

Tough Bidding Norms Slow NHAI Road Project Awards

Stringent bidding rules imposed by the Ministry of Road Transport & Highways (MoRTH) have led to a slowdown in project awards by the National Highways Authority of India (NHAI), despite a robust Rs 3.5 trillion pipeline. According to an HDFC Securities report, the shift to more cautious developer models now favours firms with strong balance sheets, as tighter qualification norms limit aggressive bidders.The revised norms mandate additional performance security, targeting the exclusion of players that previously submitted low bids—often 25 to 40 per cent below NHAI cost estimates—raisin..

Next Story
Infrastructure Transport

Mumbai Gets Coastal Nod for Next Promenade Phase

As Mumbai prepares to open two major sections of its expansive seafront promenade this week, the city’s civic authority has secured a key coastal clearance to advance further construction. The Maharashtra Coastal Zone Management Authority (MCZMA) has approved the commencement of work on the segment between Haji Ali and Baroda Palace, with tendering expected soon after project cost assessments.The promenade, stretching 7.5 km in length and 20 metres wide, is being designed as a flagship open space for walkers, joggers, and cyclists. Two critical stretches—2.75 km from Tata Garden to Haji Al..

Advertisement

Subscribe to Our Newsletter

Get daily newsletters around different themes from Construction world.

STAY CONNECTED

Advertisement

Advertisement

Advertisement

Talk to us?