Materials of the Modern London Bridge: Concrete, Steel, Granite

The London Bridge that stands today (opened 1973) is a composite of three primary materials, each chosen for specific structural and aesthetic roles:

1. Reinforced Concrete – The Skeleton

The entire load-bearing structure—piers, abutments, and the continuous box-girder deck—is cast-in-place reinforced concrete.

• High compressive strength handles the dead/live loads of a 928-ft span.
• Post-tensioned steel tendons within the concrete counteract tension (concrete's weakness), enabling the shallow, efficient box-girder profile.
• Durability: dense, low-permeability mix with cover to protect rebar from Thames chlorides.

2. Steel – The Muscle

• Reinforcement: Deformed high-yield bars (rebar) throughout the concrete.
• Bascules: The two movable leaves (lifting sections) are steel fabrications—lightweight, high tensile strength, fatigue-resistant for repeated opening cycles.
• Bearings & Joints: Steel rocker/roller bearings accommodate thermal expansion/contraction.

3. Granite – The Skin

• All exposed concrete faces are clad in Cornish granite (same source as Rennie's 1831 bridge).
• Functions: weather shield (granite is virtually impervious to freeze-thaw, salt, pollution), architectural dignity (connects visually to the historic stone bridges), low maintenance (no painting, no staining).
• Panels are precision-cut, mechanically fixed to the concrete backing.

Why This Trio?

Concrete for bulk/compression, steel for tension/movement, granite for permanence/beauty. It's a material hierarchy that defines modern bridge engineering—wrapped in a stone veneer that honors the site's 2,000-year lineage.