China uses stainless steel for Hong Kong-Zhuhai-Macau bridge to keep it corrosion free for century
In a global showcase of advantages of using stainless steel in the corrosion-prone coastal areas, China has built a 55 km long Hongkong – Zhuhai – Macau bridge using around 10,000 tonnes of stainless steel, among other metals. Chinese President Mr Xi Jinping inaugurated the bridge on October 23, 2018 for public use. The bridge has used over 10,000 tonnes of nickel containing duplex stainless steel reinforcement bars in construction at critical corrosive zones. This is expected to ensure a projected life of 120 years for the structure, which will be under constant corrosive attack of saline sea water. This landmark structure is a bridge tunnel system consisting of a series of three cable stayed bridges, one 6.7 km under sea tunnel, and 3 artificial islands. The bridge is an engineering marvel constructed over 9 years, at an estimated cost of $20 billion.
Commenting on the misplaced perception of stainless steel among users, ISSDA’s President, Mr K K Pahuja said, “Stainless steel ensures long and maintenance free structures, leading to cumulative savings and low lifecycle cost. The perception of high cost of stainless-steel reinforcement bars is misplaced. Indian stainless steel reinforcement bar standard has six grades for different applications at different price points to optimize costs”. The stainless steel rebars can also be used selectively in high corrosive zones, like in the Hongkong – Zhuhai – Macau bridge zone. “If used selectively, the impact on the total initial cost of the project may be just 1-2%, but it may lead to much bigger savings on other factors by eliminating problems like rebar coatings, cement inhibitors, concrete sealers, membranes, and thicker concrete overlay, as well as financial loss due to traffic and commercial upsets. Only stainless steel reinforcement bars of suitable grades should be used in all forthcoming marine projects in Mumbai like coastal roads and sea links, in the interest of long-term sustainability”, he added.
India has a vast coastline, ranging over 7000 kilometers, comprising 9 states and 4 union and island territories. Infrastructure in these areas faces saline moisture attack, which causes serious corrosion, impacting its strength, safety and longevity. India adopted a stainless steel reinforcement bar standard IS 16651 in 2017. However, the users are yet to realize its potential and benefits, and hence, continue to use other traditional materials. Low awareness about this product and perception of high costs deter users to consider stainless steel, even in corrosive coastal and marine environments. Usage of duplex stainless steel rebars can lead to a life of up to 125 years and provide cost advantage on lifecycle cost, as compared to carbon steel rebars being used in social infrastructures. Indian Stainless Steel Development Association (ISSDA), the industry body for stainless steel, has been effectively sensitizing government authorities and end users on the issue.