A Chinese research team has developed an ultra-lightweight foam concrete that could transform runway safety systems. Nicknamed “marshmallow concrete” for its soft, crushable structure, the material is designed to gently decelerate aircraft during emergency landings, offering a reliable and sustainable alternative to traditional runway buffers.

Lightweight Material with High Impact Absorption

The China Building Materials Academy led the development, working alongside the China Academy of Civil Aviation Science and Technology. Their concrete features over 80 per cent porosity and weighs just 200 kilograms per cubic metre—only a tenth of standard concrete. This design allows it to absorb impact by crumbling in a controlled way, creating a soft but effective barrier for aircraft.

Unlike sand or water-based safety zones, which can freeze or degrade in poor weather, this concrete remains stable. Its performance doesn’t depend on temperature or humidity, making it a dependable option year-round.

Engineered for Aircraft Like the Boeing 747

To stop aircraft smoothly, the material must stay within a very tight strength range—between 0.30 and 0.35 megapascals. Most concrete aims for higher strength, but this version is intentionally weaker and more responsive to impact. It absorbs energy without causing damage to the aircraft or bouncing it back.

Rather than using expensive calcium sulfoaluminate cement, the researchers opted for conventional cement. They developed a custom foaming process using a twin-chain, rosin-based air-entraining agent. This additive stabilises the concrete’s bubbles by forming a durable shell around each one, preventing collapse during impact.

Designed for Durability and Cost Efficiency

The team also introduced a two-stage strength regulation method. This system gradually increases the concrete’s strength, allowing it to adapt to environmental changes over time. As a result, the material maintains its performance even after long-term outdoor exposure.

The foam concrete system has already been installed at 14 airports in China. One site, located in Nyingchi in Tibet, showed less than 3 per cent change in performance after a full year—well below the 10 per cent safety threshold.

Potential for Broader Design Applications

Although designed for aviation, this material offers potential across several design disciplines. Architects and civil engineers could apply its energy-absorbing properties in urban infrastructure or public space design. Its lightweight, low-resource composition aligns with circular and sustainable construction principles, making it relevant for projects that prioritise material efficiency and safety.

Source: Xinhua News Agency
Photo: Nguyen Hung