be tong khi chung ap-aac

8/9/2019 Be Tong Khi Chung AP-AAC

1/8

Autoclaved Aerated Concrete

http://www.cement.org/homes/ch_bs_autoclaved.asp

Concrete Home > Building Systems > Autoclaved AeratedConcrete

Autoclaved aerated concrete, or AAC, is made with fine aggregates,cement, and an expansion agent that causes the fresh mixture torise like bread dough. In fact, this type of concrete contains 80% air.In the factory where it is made, the material is molded and cut intoprecisely dimensioned units.

Cured blocks or panels of AAC are joined with thin bed mortar.Components can be used for walls, floors, and roofs. The lightweight

material offers excellent sound and thermal insulation, and like allcement-based materials, is strong and fire resistant. In order to bedurable, AAC requires some type of applied finish, such as apolymer-modified stucco, natural or manufactured stone, or siding.

More information on AAC is available from the Autoclaved AeratedConcrete Products Association. From codes and standardsdevelopment to education and marketing, AACPA supports thesuccess of autoclaved aerated concrete products and the

mainstreaming of AAC into North American construction.

Advantages

AAC combines insulation and structural capability in onematerial for walls, floors, and roofs. Its light weight/cellularproperties make it easy to cut, shave, and shape, accept nailsand screws readily, and allow it to be routed to create chasesfor electrical conduits and small-diameter plumbing runs. This

gives it design and construction flexibility, and the ability tomake easy adjustments in the field.
http://www.cement.org/homes/ch_bs_autoclaved.asphttp://www.cement.org/homes/ch_bs_autoclaved.asp


2/8

Durability and dimensional stability. A cement-based material,AAC resists water, rot, mold, mildew, and insects. Units areprecisely shaped and conform to tight tolerances.

Fire resistance is excellent, with 8 in. thick AAC achieving a 4-

hr rating (actual performance exceeds that and meets testrequirements for up to 8 hr). And because it is noncombustible,it will not burn or give off toxic fumes.

The light weight means that R-values for AAC are comparableto conventional frame walls, but they have higher thermalmass, provide air tightness, and as just noted, are notcombustible. That light weight also gives a high soundreduction for privacy, both from outside noises and from other

rooms when used as interior partition walls.

But the material does have some limitations. It is not as widelyavailable as most concrete products, though it can be shippedanywhere. If it has to be shipped, its light weight is advantageous.Because it is lower strength than most concrete products or systems,

in load-bearing applications, it must typically be reinforced. It alsorequires a protective finish since the material is porous and woulddeteriorate if left exposed.

Sizes

Both blocks and panels are available. Blocks are stacked similarly toconventional masonry, but with a thin-bed mortar, and panels arestood vertically, spanning full-story heights. For structural needs,

grouted, reinforced cells and beams are placed within the wallsection. (Concave depressions along vertical edges can create acylindrical core between 2 adjacent panels.) For usual applications, a


3/8

vertical cell is placed at corners, on either side of openings, and at 6-to 8-ft spacings along a wall. AAC averages about 37 pcf (lbs per cuft), so blocks can be placed by hand, but panels, because of theirsize, usually require a small crane or other piece of equipment.

* Panels extend from floor to top of the wall: Height: up to 20 ft

Width: 24 in.

Thickness: 6, 8, 10, or 12 in. (4 in. thick interiorpartition panels are available)

* Blocks are larger and lighter than traditional concretemasonry:

Height: 8 in. typical Width: 24 in. long

Thickness: 4, 6, 8, 10, and 12 in.

A standard 8 x 8 x 24 in. unit weighs about 33lbs.

* Specialty shapes:

U-shaped bond beam or lintel blocks are available inthicknesses of 8, 10, and 12 in.

Tongue and groove blocks are available from somemanufacturers, and these connect to adjacent unitswithout mortar at vertical edges

Cored blocks available for creating verticalreinforced grouted cells

Installation, Connections, and Finishes


4/8

Due to the similarity to traditional concrete masonry, AAC units(block) can be easily installed by concrete masons. Sometimes,carpenters get involved in installation. Panels are heavier due totheir size and require the use of a crane for placement.Manufacturers offer training seminars, and its usually adequate tohave 1 or 2 knowledgeable installers on small projects. Dependingon the type of finish selected, they can be directly adhered ormechanically attached to the face of AAC.

* Block

First course is laid and leveled. Blocks are stackedtogether with thin-bed mortar in a running bondwith a minimum of 6-in. overlap.

Walls are plumbed, leveled, and squared with a

rubber mallet. Openings and odd angles are cut with a handsaw or

bandsaw.

Reinforcement locations are determined, rebarplaced, and grouting occurs. Grout must bemechanically vibrated to consolidate it.

Bond beams are placed at the top of the wall andcan be used for heavy-duty fixture attachment.

* Panels

Panels are placed one at a time, starting from thecorner. Panels are set into a layer of thin-bed mortarand vertical rebar is attached to dowels extendingup from the floor before the adjacent panel isplaced.

A continuous bond beam is created at the top, eitherwith plywood and AAC material or with bond beamblock.

Openings can be precut or field cut.

* Connections Roof frame/framing is connected to a conventional

top plate or hurricane straps embedded in the bondbeam.

Floor framing is attached with standard ledgersanchored to the side of the AAC assembly adjacentto a bond beam.

AAC floor systems bear directly on top of AAC walls.

Larger structural steel members are set on weldplates or bolt plates set into the bond beam.

* Finishes


5/8

Stucco-type finishes are made specifically forAAC. These polymer-modified plasters sealagainst water intrusion yet allow moisturevapor for breathability.

Conventional siding materials are mechanically

attached to the wall face. Furring strips shouldbe employed if back ventilation of the sidingmaterial is desirable.

Masonry veneers can be directly adhered tothe wall face or can be built as cavity walls.Direct-applied veneers are typically lightweightmaterials like manufactured stone.

Sustainability and Energy Considerations

AAC offers both material and performance aspects from asustainability perspective. On the material side, it can containrecycled materials like fly ash and rebar, which may help contributeto credits in LEED or other green rating systems. Further, itincorporates such a large quantity of air that it contains less rawmaterial per volume than many other building products.

From a performance perspective, the system leads to tight buildingenvelopes. This creates an energy efficient envelope and protects

against unwanted air losses. Physical testing demonstrates heatingand cooling savings of roughly 10% to 20% compared toconventional frame construction. In consistently cold climates, thesavings may be somewhat less because this material has lowerthermal mass than other types of concrete. Depending on thelocation of manufacturing relative to the project site, AAC may alsocontribute to local materials credits in some green building ratingsystems.


6/8

Manufacturing and Physical Properties

First, several ingredients are blended into a slurry: cement, lime,water, finely ground sand, and often, fly ash. An expansion agent

like aluminum powder is added and the fluid mixture is cast into alarge billet. As the slurry reacts with the expansion agent togenerate air bubbles, the mixture expands. After its initial set, theresulting cake is wire cut into precisely sized blocks or panels andthen baked (autoclaved). The heat helps the material to cure fasterso that blocks and panels maintain their dimensions. Reinforcementis placed within panels prior to curing.

This manufacturing process produces a lightweight, noncombustible

material with the following properties:

Density: 20 to 50 pcf (lb per cu ft)this is light enough to floatin water

Compressive strength: 300 to 900 psi

Allowable shear stress: 8 to 22 psi

Thermal resistance: 0.8 to 1.25 per in. of thickness

Sound transmission class (STC): 40 for 4 in. thickness; 45 for 8

in. thickness

Building Code Issues


7/8

After introduction as an appendix in the 2005 Masonry Standards Joint Committee document, design of AAC masonry became morestandardized (see the 2008 MSJC Code). In the 2011 version of theMSJC, the information will appear in the main body of the documentand the appendix will be dropped. The code addition of AAC as astructural masonry system removes a potential hurdle for use of thematerial by designers and builders. With AACs inclusion in the code,the International Building Code and International Residential Codefrom the International Code Council now reference MSJC forinformation related to autoclaved aerated concrete.

In addition, the American Concrete Institute 523 committeepublished a guide in 2009 entitled Guide for Design and Constructionwith Autoclaved Aerated Concrete Panels (523.4R-09). Its purpose isto present information that can help in the design, specification, and

construction of factory-reinforced panels of autoclaved aeratedconcrete (AAC).

Autoclaved Aerated Concrete Products Association

The Autoclaved Aerated Concrete Products Association's mission isto nurture and chanpion the autoclaved aerated concrete (AAC)industry, by creating and maintaining a dynamic network bringingtogether resources, knowledge, and innovation.

7638 Nashville St.

Ringgold, GA 30736

(706)965-4587 / Fax: (706) 965-4597

www.aacpa.org

AAC Projects:

A Tale of 3 Cities: The Residential Versatility of AAC

The benefits of using autoclaved aerated concrete (AAC) arenumerous. Perhaps in testament to the versatility of AAC, the 3residential projects described here are quite differentbut share acommon theme of safety. A large single family home in a forest,whose construction is being managed by the owner himself; amodest single family home on a wooded site, designed by anarchitect seeking environmentally sound and healthy living; and a

large development along the Louisiana Gulf Coast requiring superiorweather resistance. More on AAC residential projects.
http://www.aacpa.org/http://www.aacpa.org/


8/8

The " Suite " Comfort of Concrete

Some guests in a Georgia hotel are sleeping better tonight thanks toautoclaved aerated concrete (AAC). About an hour outside ofAtlanta, the site for the Forsyth, Georgia Comfort Suites, a slim lot

adjacent to an interstate, posed a few challenges. And high landcosts are making it increasingly common to build on sites that haveinherent challenges such as noise, unlevel terrain, or minimal set-backs. So developers turned to a concrete system to help meet theirneeds for delivering a quality projectin this case, a strong, quiet, 4-story structure near a heavily traveled highway. More on the AAChotel.

Disclaimer

The listing of organizations and information resources constitutesneither an endorsement nor recommendation by the PortlandCement Association (PCA). PCA disclaims any and all responsibilityfor the selection of organizations listed and the products theyrepresent. PCA also assumes no responsibility for errors andomissions in this list.

be tong khi chung ap-aac

Documents