Just when the masonry arch bridge was reaching its peak around the beginning of the 20th Century, reinforced concrete arrived on the scene. Since then, it has become the major construction material for bridges as it has for most structural and civil engineering applications, with its intrinsic versatility, design flexibility and, above all, natural durability.

Although several British engineers had been using concrete early in the 19th Century, its use in British bridges did not develop until the latter half of the 20th Century. The use of reinforced concrete probably started with the Homersfield Bridge over the River Waveney on the Norfolk/Suffolk border in 1870, when iron was embedded in concrete, but it was not until the first decade of the 20th Century that reinforcement, as we know it today, was introduced. It is uncertain when precast concrete was introduced but early applications revolved around railway footbridges, with Southern Region leading the way at Oxshott, Surrey (1908) and Exeter (1923). An outstanding precast structure of the time was at Mizen Head, Cork (1908).

The outstanding feature of concrete bridges both during and after the Second World War was the advent of prestressed concrete, used to rebuild the many bridges that had been destroyed, especially on the Continent.

In the UK, a stock of emergency prestressed concrete beams was held during the War and used afterwards in permanent bridgeworks. They were designed by Dr. Mautner of the Prestressed Concrete Company, a subsidiary of Mouchel licensed by Freyssinet. This partnership was responsible for Nunn's Bridge, Fishtoft near Boston (1948), the first in-situ prestressed concrete road bridge.