Asia Pacific Infrastructure: August - September 2021

Page 94

August - September 2021

Preventing collapsing structures

Sponsored Article

Sustainable construction has become a goal for owners across the globe, says Cortec’s Ivana Liposcak

CONSTRUCTION

O

ften overlooked is the durability and service life for the final structure. This is undoubtedly one of the main factors influencing structural sustainability. Durability is the basis for the preservation of reinforced concrete structures long-term. The durability depends on a good and professional choice of materials that help to avoid damage. If damage has occured, rehabilitation should be approached with great care with the selection of a product that is compatible with material used during construction. The durability and design of structural lifetime is often around 50 years, but it can be greatly extended with regular maintenance Crumbling Infrastructure Is a worldwide problem and maintenance is essential to avoid fatal tragedies like the recent Florida collapse. Even though some engineers argue that corrosion on its own was unlikely to bring down the building, it could have been a critical issue if it occurred on or near the supporting columns and was progressive. What exactly happened with this residential building is still to be finally determined but current evidence indicates that rebar corro94 propertyandbuild.com

sion and concrete spalling might have caused the structural failure. Harsh environmental effects in Florida on steel and concrete structures are well known. Reports point to abundant cracking and spalling in the concrete columns, beams and walls in the parking garage located under the building. In 2018, the Morandi bridge collapsed in Genoa, Italy—another tragic accident indicating how neglecting corrosion can have fatal consequences. Engineers voiced concerns about its unusual concrete-encased common steel cables. The designer of the bridge had warned decades ago that it would require constant maintenance to remove rust, given the effects of corrosion from sea air and pollution on the concrete. Also, the problem of fatigue corrosion on metal elements, particularly insidious in steels of high mechanical strength such as strands, is still a little-known subject. “As this reinforced and prestressed concrete bridge has been there for more than 35 years, corrosion of tendons or reinforcement was a contributory factor,” said Ivana Liposcak, Cortec’s Migratory Corrosion Inhibitor (MCI®)

technical support manager for Europe. “The long-term behavior of viaducts subjected to heavy traffic and situated in [an] aggressive environment shows that at the time of planning, obviously many concepts about the sustainability of the bridge were not known and considered. “Due to the vibration in concrete, microcracks occur, through which the moisture leads to oxidation and corrosion of steel and in that way, [the] structure gradually loses its capacity due to corrosion,” says Liposcak. In the last two decades there have been huge advances in technology to extend the lifespan of structures and avoid possible tragedies. Patented MCI® technology was designed to protect reinforcing metal in concrete from corrosion. By using this technology, corrosion initiation is delayed, and the lifecycle of structures is

significantly extended. The Maslenica Bridge in Croatia, one of the largest bridges of its type with an arc of 200 meters in diameter. Because of the aggressive environment of changing temperatures, constantly fluctuating humidity, and strong wind containing salt from seawater, reinforcing steel had started to corrode, causing concrete spalling. To restore the bridge and prevent future corrosion from happening, all spalling concrete was water-blasted off, along with dirt and corrosion on the rebar. CorrVerter® MCI® Rust Primer was brushed on exposed rebar to passivate the metal from further corrosion, and MCI®-2020 was applied to the entire concrete structure using an airless sprayer to prevent any potential corrosion that was not apparent. www.cortecvci.com


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Articles inside

Further mortgage restrictions coming as house price growth continues

7min
pages 102-106

Is this the turning point of New Zealand’s property market?

6min
pages 100-101

Property investor confidence hits record highs

12min
pages 96-99

Preventing collapsing structures

2min
page 94

Kiwi innovation leading the way in concrete slab insulation

2min
page 95

Will the reformed RMA actually help deliver more housing?

5min
pages 88-90

Australia to slash planning times by 25 percent

1min
page 91

Facilities management with personal service

1min
pages 82-83

Residential construction reforms save time and improve quality control

10min
pages 84-87

China builds 10-storey tower in a day

1min
page 81

Chemical safety relies on meaningful cooperation

3min
pages 76-80

Infrastructure Skills Centre offers “work experience for a lifetime”

3min
pages 74-75

Safety app a crucial element in building site safety

3min
pages 72-73

Cordless machines and safer technologies will save lives

11min
pages 66-70

Is standardised training the way forward?

2min
page 71

Unlearning misguided muscle training keeps you pain free at home and work

6min
pages 62-63

Tips and myths around dogs

2min
pages 60-61

Safety focus on crane service standards

4min
pages 64-65

Bastion NZ launch Industrial glove range

1min
pages 58-59

Industry leader in soft fall protection on construction sites

2min
pages 56-57

Wood waste to take aluminium's place in food packaging

1min
page 35

No better investment than chemical safety training

3min
page 45

Thermal recycling - part of the solution not part of the problem

9min
pages 31-34

Scholarships supporting tomorrow’s health and safety leaders

1min
pages 52-53

What is workplace harassment and how to prevent it

2min
pages 54-55

How to become a successful green business

5min
pages 29-30

Winning the last mile in the supply chain race

2min
page 36

Can a vaccine for cattle help the dairy sector cut methane emissions?

6min
pages 27-28

The three paths to net-zero

5min
pages 20-22

The consequences of banning oil and gas exploration

4min
pages 25-26

Is hydrogen the future of energy?

4min
pages 23-24

AC Filter - an engineered solution protecting worker health

1min
page 13

Are we forgetting national self-sufficiency?

6min
pages 4-9

Schneider: data centres and smart homes

6min
pages 10-12

In search of the perfect surface - contractor invents new earth compactor

2min
pages 14-15

Climate change kicks into gear

3min
page 3
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