A review of autoclaved aerated concrete products

Abstract

This report is a review of the properties and performance of autoclaved aerated concrete. The material has a relatively low thermal conductivity combined with loadbearing capacity for use in structural and non-structural applications. This feature may make its use attractive for energy-conserving applications. For this reason, the review was conducted at the request of the U.S. Department of Energy.The review addressed an overview of the manufacturing process, uses of autoclaved aerated concrete in building constructions, properties, energy considerations, the availability of code-related documents, and standards. Uses include block and panel construction in both loadbearing and non-loadbearing applications for walls, floors, and roofs. Many properties are reviewed including density, fire resistance, moisture expansion and shrinkage, strength, structure, and thermal conductivity. With regard to energy considerations, the review points out that, for energyefficient applications under severe climatic conditions, the autoclaved aerated concrete unit alone may be insufficient to provide the targeted minimum value of thermal resistance. In these cases, autoclaved aerated concrete has to be used together with additional thermal insulation. In contrast, autoclaved aerated concrete alone may satisfy insulation needs in areas having mild climates.

Evaluation of the Physical and Mechanical Properties of Autoclaved and Foamed Concrete Blocks Marketed in Passo Fundo/RS Brazil

“…According to Mathey and Walter J. Jr. Rossiter (1988), water absorption for the autoclaved concrete is neglected because it is considered low, but the results found in this assay indicated that the amount of water absorbed was high.…”

“…In Brazil, NBR 13438 (ABNT, 2013a) defines autoclaved aerated concrete blocks (AACB) as lightweight concrete which is prepared by adding aluminum powder and then the mixture undergoes a steam-saturated curing process under controlled pressure (12 atm) at a temperature of between 180°C and 200°C. According to Mathey e Walter J. Jr. Rossiter (1988), this curing process allows the material to have resistance strengths above 1.5 MPa and densities of around 500 kg/m 3 , and this also results in well-distributed spherical pores with low capillarity.…”

Insulation failure of lightweight composite sandwich panels exposed to flame

“…Due to the severe adverse effects of shrinkage in the concrete, researchers suggested that lightweight aerated concrete in non-load bearing elements should not be subjected to temperature above 700 C since major cracks and collapse can occur above that temperature. 8,[13][14][15][16] Over the years, the behaviour of composite sandwich panels and their performances during exposure to elevated temperatures and fire events were investigated. Vilches et al 12 evaluated the performance of ultra-lightweight foam concrete with varying densities of 150 to 500 kg/m 3 , enduring elevated temperature from 1 hour to more than 3 hours depending on the cement percentage and density.…”

“…Furthermore, concrete could be prone to shrinkage phenomenon when it was subjected to dry conditions such as high temperature or fire events. Due to the severe adverse effects of shrinkage in the concrete, researchers suggested that lightweight aerated concrete in non‐load bearing elements should not be subjected to temperature above 700°C since major cracks and collapse can occur above that temperature 8,13‐16 …”

Implementation and validation of a 3D image-based prediction model for the thermal conductivity of cellular and granular porous building blocks

“…Hence, they require to be used in combination with load-carrying elements like solid bricks or concrete slabs. Porous building blocks, on the other hand, aim to combine both load-carrying and thermal insulation capacities [1][2][3]. Well-known commercial variants are cellular glass or cellular concrete.…”