Reinforced Autoclaved Aerated Concrete

Following the SCOSS newsletter 58 in April 2020, there has been increased concern regarding Reinforced Autoclaved Aerated Concrete. As the note says “Autoclaved aerated concrete (AAC) is different from normal dense concrete. It has no coarse aggregate, and is made in factories using fine aggregate, chemicals to create gas bubbles, and heat to cure the compound. It is relatively weak with a low capacity for developing bond …..”

In carrying out concrete repairs, it should be noted that most concrete repair materials are designed for use on normal concrete, which has higher strength. Any repair needs to understand the properties of the repair material and parent material. Repairing RAAC needs careful consideration as the materials available are typically denser than RAAC and the required bond strength to hold them in place in the RAAC may not be available.