What Is the Density of Standard Concrete Building Blocks?

Description

• Standard concrete building block is a precast, rectangular concrete brick that may be solid or have two or three hollows, or openings, that run the width of the block. The blocks are used to build commercial and residential structures. Common materials used to create a concrete block include Portland cement and aggregate — aggregate is crushed rock. Concrete blocks with a high density are created using a smaller aggregate such as sand or finely crushed stones or rock. Low-density blocks may use volcanic or coal combustion cinders or recycled masonry instead of aggregate. Standard concrete building blocks are also called a cement block, concrete masonry unit, also known as a CMU, cinder blocks or foundation block.

Types

• Concrete building blocks are designed for specific purposes and standard block is designed in two ways: to have a smooth exterior surface along one end and an indention at the other end that accepts mortar or with an indention at both ends. Concrete block with a smooth end is used for corner details — some manufacturers make building block with a bullnose detail for a round look. Jamb blocks, sash units and headers are specialty concrete blocks with special shapes designed to be used to frame windows, doors and walls. For instance, sash block is used at a door jamb and has an L-shape cut from one of its ends so that the block fits around the jamb.

Materials

• The materials used in creating a concrete building block define the density of the block. Blocks made with recycled masonry — crushed brick or concrete block -- or combustion cinders, instead of crushed aggregate, will often have less density than blocks made from freshly crushed aggregate or stone. A less dense block is a lighter block to carry and work with but may not meet basic building code requirements for concrete block.

Density

• It is important to note when speaking of a concrete building block, the term “standard” is usually a reference to the size and shape of the block and not necessarily the density or materials from which the block is made. Concrete block comes in variety of densities, according to the National Concrete Masonry Association and the Masonry Advisory Council. Density for a concrete block is measured as pounds per cubic foot and noted as “pcf.”

  The Masonry Advisory Council website states that the density of concrete block can vary from 85 to 140 pcf and higher. According to MAC, concrete block falling between 85 and 140 pcf is within the quality standards set by the ASTM for concrete masonry. The ASTM is formerly known as the American Society for Testing and Materials and may be referenced in local building codes.