Reinforced autoclaved aerated concrete

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RAAC ceiling Panels
Department of Education (UK) report: RAAC Guide
RAAC wsll panels
Department of Education (UK) report: RAAC Guide
RAAC fragment
Department of Education (UK) report: RAAC Guide

Description

A lightweight, ‘bubbly’ form of concrete masonry blocks and pre-cast panels commonly used in construction between the 1950s and mid-1990s. Autoclaved Aerated Concrete (AAC) was made using a fine aggregate mixed with chemicals to create gas bubbles then cast with a metal reinforcement (RAAC) network and cured with high heat. The result was a relatively weak concrete that had poor load-bearing ability and weak bonding with its embedded metal reinforcement. RAAC pre-cast panels were predominantly used in roofs (commonly flat roofs, sometimes pitched) and occasionally in floors and walls. The panels are light-grey or white in appearance, with a smooth, paintable surface. The inside of the planks will appear bubbly, often described as looking like an Aero bar. Unlike traditional concrete, there will not be visible stones (coarse aggregate) in the panels. The panels have distinctive V-shaped grooves at at the connection points (every 600 mm). A bituminous or latex coating was sometimes added as a water barrier.

Synonyms and Related Terms

RAAC; Reinforced AAC

Risks

  • Cracking and spalling
  • Load-bearing failure
  • Corrosion of metal reinforcements
  • Movement and deflections of panels

Forms and Sizes

  • Typically 600 mm wide panels

Resources and Citations

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