SP-226 Since its inception more than 80 years ago, autoclaved aerated concrete (AAC) has enjoyed a reputation for excellent thermal insulation, acoustic, and fire-resistant properties due to its low density and cellular structure. The production and use of AAC in the United States, however, did not start until the mid 1990s. To promote and encourage the use of AAC and other ultra-lightweight concrete, ACI Committee 523, Cellular Concrete, and ACI Committee 229, Controlled Low-Strength Materials, organized a technical session on "Controlled-Density/Controlled-Strength Concrete Materials at the 2003 ACI Spring Convention in Vancouver, Canada, and a session on "Aerated Concrete - An Innovative Building Solution" at the 2003 ACI Fall Convention in Boston. Thirteen papers were presented at these two technical sessions covering a wide range of practical case studies and research projects on different types of ultra-lightweight concretes, with particular focus on AAC. These papers should be of interest to the practicing engineers, educators, and researchers in that they demonstrate the effective use of AAC as well as other types of ultra-lightweight concrete materials. This special publication (SP) contains eight of the 13 papers presented at the session. Six of the papers deal with AAC and cover a wide variety of topics including material properties, structural design, seismic performance, and design examples. The other two papers address the acoustic and structural properties of foamed and/or aerated lightweight concretes cured at room temperature.

A general overview of the approach to the design of autoclaved aerated concrete (AAC) structural walls and floor/roof panels is presented. Variations in design approach from concrete and masonry, and design equations specific to AAC are discussed and provided. Design examples illustrate the proposed approach.

Three classes of specialty cementitious materials were evaluated for their potential benefits in sound absorption including a Foamed Cellular Concrete (FCC) with density ranging from 400 – 700 kg/m3, Enhanced Porosity Concrete (EPC) incorporating 20-25% open porosity, and a Cellulose Cement Composite (CCC) with density 1400 – 1700 kg/m3. Cylindrical specimens of these materials were tested for acoustic absorption in an impedance tube. The FCC specimens showed absorption coefficients ranging from 0.20 to 0.30, the higher value for lower density specimens. The closed disconnected pore network of FCC hinders sound propagation, thereby resulting in a reduced absorption, even though the porosity is relatively high. The most beneficial acoustic absorption was observed for EPC mixtures. When gap-graded with proper aggregate sizes, these no-fines EPC mixtures dissipate sound energy inside the material through frictional losses. The cellulose fiber cement composites use cellulose fibers at high volume fractions (~7.5%), which are believed to provide continuous channels inside the material where the sound energy can be attenuated. By engineering the pore structure (by careful aggregate grading as in EPC, or incorporating porous inclusions like morphologically altered cellulose fibers) cementitious materials that have the potential for significant acoustic absorption could be developed.

Autoclaved aerated concrete (AAC) is a lightweight uniform cellular material, first developed in Sweden in 1929. Since that time, plain and reinforced AAC building components have been widely used in Europe and other parts of the world. Until recently, however, AAC was relatively unknown to the United States precast construction market. Today, AAC prefabricated elements are gaining rapid acceptance in the United States due primarily to increasing energy cost, environmental concerns, and the ease of construction using AAC elements. Although AAC is a well-recognized building material in Europe, very little research work has been done on U.S.-produced AAC products. The primary objective of this work was to study the structural behavior of U.S.-made reinforced AAC elements. The laboratory test program included most commonly used reinforced AAC elements: floor panels, lintels, and wall panels. Two U.S. manufacturers supplied the AAC elements. Floor panels and lintels were tested in bending, whereas the wall panels were tested under axial or eccentric loading. The ultimate load capacity, cracking, deflection, and failure mode were observed and recorded for each test. The results provide a database that will be used to refine the analytical methods for the structural design of reinforced AAC elements. This information is needed to enhance AAC design methodologies and lay the foundation for establishing AAC as a reliable engineered construction material in the U.S.

This paper is a summary of ACI 523.5R, which is a guide for using autoclaved aerated concrete panels. Its design provisions are non-mandatory, and are a synthesis of design recommendations from the Autoclaved Aerated Concrete Products Association, and from the results of research conducted at the University of Alabama at Birmingham (UAB), the University of Texas at Austin (UT Austin), and elsewhere. This paper discusses the design equations associated with the various typical structural uses of autoclaved aerated concrete. Those uses include flexural, axial compression, shear, bearing, bond and development of reinforcement and special seismic design provisions. The design provisions of this Guide are not intended for use with unreinforced, masonry-type AAC units. Design of those units is covered by provisions currently under development within the Masonry Standards Joint Committee.