Guizhou's mega-bridge sets fire safety milestone

As Guizhou province prepares to unveil the world's tallest bridge, its main suspension cables are receiving a fireproofing and anticorrosion treatment, which is said to withstand 1,100 C flames for a full hour without so much as a singe.

Measuring 2,378 meters, the main cables of the Huajiang Grand Canyon Bridge are vital components designed to bear the bridge's weight. Wrapped in protective wire and multiple layers of sealant, they are engineered to resist rust and extreme heat. Each main cable consists of 217 compacted strand bundles, which in turn contain 91 high-strength, 5.7 mm steel wires.

Nearly 100 workers have labored around the clock on the bridge's catwalks to complete this monumental task.

"Fire-resistance standards take into account the worst-case scenario, such as an oil tanker catching fire on the bridge deck," explained treatment project leader Wu Huijuan. "An exploding fuel truck can raise temperatures to around 1,000 C. That's why we set our design threshold at 1,100 C. Even if a tanker burns for an hour, the cables remain unscathed. Our firefighting systems and protocols ensure rescue crews can always arrive within that window."

Technician Tian Hongrui of Guizhou Bridge Construction Group detailed the process: "First, we wrap the main cable in tightly spun wire using a specialized machine, creating a sealed barrier against moisture, rain and corrosion."

Once the wire wrap is in place, up to five layers of fire-resistant sealant are applied, depending on the location of the cable. "The core protection layer is a basalt-fiber fabric infused with aerogel, which boosts insulation," Wu added. "It's then covered with flame retardant sealing tape to form a strong shell, with the outermost wrapping that can withstand temperatures up to 1,200 C."