Solution Summary: AAC (Aerated Autoclaved Concrete)
Aerated autoclaved concrete (AAC) block is a substitution material that can reduce musculoskeletal disorders (MSD) from manual material handling. It is a lightweight concrete block that can be used as an alternative to standard concrete masonry units (CMU) in certain applications, such as low rise loadbearing buildings, partition walls, infill walls, shear walls, etc.
Aerated autoclaved concrete (AAC) block is a lightweight building material used in commercial, industrial and residential sites in the place of standard concrete masonry units (CMU). It was introduced to the U.S. from Europe in the past two decades. AAC has several properties such as: a) the ability to provide thermal and acoustic insulation, b) lightweight, c) energy conservation, d) durable, e) fire and pest resistant, and f) versatile and easy to use.
Standard AAC blocks weigh approximately 30lbs and are usually 24" long. They are available in different shapes and sizes: 1) AAC standard blocks, 2) AAC "O" blocks, 3) AAC "U" blocks, 4) AAC open end blocks, and 5) AAC jumbo blocks (Figure 1).
Figure 1. Variety of AAC blocks (Photo courtesy of E-Crete)
AAC blocks are fabricated from a mixture of lime, sand, cement, gypsum, water and aerated agent. The exterior and interior walls are easy to finish, and they can be painted, plastered, tiled or left exposed. AAC is most commonly used for interior walls and structures of two stories or less.
AAC is considered to be environmentally friendly for several reasons. The manufacturing of AAC material does not release any harmful gasses or CFCs, and all waste products can be easily recycled. Also, AAC blocks greatly reduce the amount of energy required to heat a building. The material properties of this material allow it to behave like a thermal mass storeroom, storing solar energy and releasing it over time.
Heavy lifting and carrying can cause low back disorders, such as muscle strain or a disc herniation (“slipped disc”), which is bulging of disc material possibly pressing on the spinal cord or nerves that go into the leg. Aerated autoclaved concrete can help reduce MSDs caused by heavy lifting and carrying by lowering the weight of the materials.
How Risks are Reduced:
Using lightweight block such as AAC during manual material handling reduces strain and loading on mason's backs. If the weight of the materials being handled is reduced, then workers' risk of developing low back pain and related musculoskeletal disorders (MSDs) is also reduced.
Independent studies have shown a reduction in exposure to known risk factors for low back pain while using lighter weight materials. The Construction Safety Association of Ontario analyzed masonry activities to determine their potential for causing musculoskeletal disorders. The study revealed that working with standard concrete blocks (12 x 24 x 6 inches, 35-45 pounds) can expose masons to a high risk of low back injury. Back stress was reduced when the weight of the block was decreased. The study also showed that adding grips to the block reduced stress as well.
Anton et al. at the University of Iowa conducted a laboratory study to determine whether lightweight concrete block reduced physiological loads compared to standard weight block. Twenty one masons constructed two 32 block walls, seven courses high, entirely of either standard weight block or lightweight block. Muscle activity from arm and back muscles, and heart rate was measured during the wall construction. In general, muscle activity was slightly lower when masons were laying lightweight block compared to standard weight block.
Safety and health experts believe that masons will be less likely to develop musculoskeletal disorders of the back and shoulder if they are able to substitute AAC block for regular CMU.
Effects on Productivity:
There may be an increase of productivity and labor savings due to the lightweight property of AAC.
Dan Anton, PT, PhD, ATC – Eastern Washington University, and Carlos Sanchez-Marin, DDS, MS – University of Iowa
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