Steel corrosion in concrete structures leading to structural damage or failure has become one of the major issues of global concern. It plays a dominant role among the factors affecting the durability of structures. In concrete engineering, steel corrosion has caused numerous engineering accidents, resulting in incalculable economic losses and casualties. The problem of steel corrosion in reinforced concrete is increasingly drawing worldwide attention.
In North America, steel corrosion in concrete structures has become a serious problem, costing tens of billions of dollars. Conservative estimates show that the total annual cost of corrosion to the U.S. industrial sector exceeds $300 billion.
By 1986, the United States had spent $24 billion on repairing corroded bridges, with the cost increasing at a rate of $500 million per year. A 1984 U.S. report indicated that 575,000 reinforced concrete bridges suffered from steel corrosion damage, among which 40% required $5.4 billion for repairs to address insufficient bearing capacity and strengthening works.The I-35W reinforced concrete highway arch bridge spanning the Mississippi River in Minnesota, USA, built in 1967, developed severe corrosion after only more than 20 years of service. It was repaired by local patching, but cracks and corrosion reappeared soon afterward without timely and effective measures taken. Eventually, a major collapse occurred in 2007, causing heavy casualties.
Many bridges collapsed suddenly after only 11 years of service. Bridges that require reconstruction or repair within less than 20 years of use are common, such as Penghu Bridge and Beijing Xizhimen Overpass. We must recognize that many repaired concrete structures suffer serious deterioration within a few years. The concrete repair industry is facing a major challenge: how to maintain, rehabilitate and protect concrete structures in their current condition to extend their service life.
Achieving the intended service life of existing concrete structures depends not only on initial design and construction, but also on carrying out effective maintenance and repair when problems escalate, and on performing such work accurately and efficiently. Innovative maintenance and protection technologies are needed to ensure the continued functionality of infrastructure.
At present, many repaired concrete structures suffer severe reinforcement corrosion only a few years after repair. In many cases, ongoing corrosion occurs due to the placement of new material over or adjacent to existing chloride-contaminated concrete. Corrosion results in cracking and spalling of concrete adjacent to repaired sections — this is known as the “halo effect”. Premature failure of concrete repair projects due to the halo effect has been a long-standing issue in the concrete repair industry. Solutions have typically been either very costly or unreliable.
Embedded sacrificial anodes can be applied in concrete repair to prevent the formation of new corrosion sites on adjacent reinforcement, offering a practical solution. This technology provides a low-cost, optimal alternative that extends the service life of repaired concrete structures. The method relies on anodes made of zinc, which are connected to exposed reinforcing steel in the repair area and protect the rebar through sacrificial corrosion. Since zinc is more electrochemically active than steel, it provides this sacrificial corrosion protection.
Zinc sacrificial anodes have been widely used in numerous building repair projects across the country. As a measure for anti-corrosion protection of concrete reinforcement, embedded zinc sacrificial anodes feature simple installation, reliable performance, and low one-time investment costs, making them worthy of promotion in concrete structure maintenance engineering.
