Reinforced Autoclaved Aerated Concrete (RAAC) and concrete: the differences

14 Sep 2023

Reinforced autoclaved aerated concrete (RAAC) planks derive their structural strength from metal reinforcing bars and this reinforcement needs to be protected from water ingress. Where RAAC planks have been exposed to water over a prolonged period of time corrosion weakens the bars and hence the planks. 

It is incorrect to draw comparisons to RAAC and the aircrete blocks used to build houses and low-rise commercial buildings, as these walling products do not use reinforcement. 

Traditional concrete, precast or ready-mixed, is used with reinforcement, but this concrete is resilient to water ingress and protects the reinforcing bars.

In 1999, the Standing Committee on Structural Safety (SCOSS) first recommended those responsible for buildings with pre-1980 RAAC to arrange inspections of those buildings using the material. In 2001, Reinforced Autoclaved Aerated Concrete (RAAC) was withdrawn from British design standards. In 2008 EN 12602 was published and is specific to reinforced aircrete products.

Concrete and aircrete products are not susceptible to the failures being seen in RAAC products manufactured from the 1950s to the 1980s.

Concrete is the world’s most versatile man-made material and forms the foundation and fabric of our built environment, both onshore and offshore, above ground, on the ground, and below our feet. New homes, schools, hospitals, workplaces, roads and railways, as well as the infrastructure that provides us with clean water, sanitation and energy, all need concrete. 

For more information download the MPA UK Concrete RAAC factsheet