The key to AAC's physical properties is its high air content--80% of its volume. Autoclaved aerated concrete is made by mixing portland cement, silica-bearing sand and water slurry with a finely powdered aluminum. Autoclaved aerated concrete block make a mason's job easier. They're lighter than conventional concrete block, soft enough to cut easily and those with recessed hand grips carved into the ends make grasping much easier. They're also larger, making them quicker to install than conventional concrete block and improving a mason's relative productivity. The per unit and overall weight reduction should reduce the risk of back injuries as well. Their solidity changes the way AAC block are laid. Since the block are precision cut, it is easy to keep a wall plumb and square as it goes up. Since AAC units are fully bedded, AAC joints distribute loads over a full block face to create a very strong joint. AAC can be cut and shaped with simple hand and power tools. This reduces the noise, dust and dust-related health risks of using high-speed diamond saws to cut conventional masonry units. One area is lacking, though. AAC is friable, water absorbent (similar to CMU) and not especially aesthetically pleasing , and therefore must be given a plaster-type finish or other protective veneer. However, the ease with which AAC can be cut and shaped helps to compensate for this shortcoming. The material can be easily carved and sculpted to create arches, relief, watertable courses and other traditional masonry motifs. Architects will also find it a fertile material in which to explore more innovative design expressions. The enhanced productivity and high performance levels made possible by AAC masonry will help keep masonry competitive with other building systems. Where AAC may cost more than other building systems, it may still be justified by insurance and energy savings. In an era in which young people routinely shy away from construction trades because they perceive them as difficult and dangerous, AAC offers us a new and modern image that can help recruit new talent to the industry.