An 8-by-8-by-16-inch concrete block weighs about 28 pounds. These blocks are used for a variety of different projects because they have a high compression strength of 1,800 pounds per square inch. Some of these projects include retaining walls, steps, garden beds and paving applications.
There are three main types of concrete blocks: interlocking, hollow and solid. These blocks range from being 55 percent solid to just 25 percent solid. Concrete blocks are usually classified by their weight and density. The term density, when referring to concrete blocks, refers to the type and amount of aggregates that are added to the concrete mixture. The more aggregates added to the mixture, the heavier the concrete blocks. Heavier blocks are often used as load-bearing blocks, while lighter ones are made for decorative purposes.
Before concrete blocks can be set, a solid foundation has to be created. Once the foundation is set, the blocks are usually installed with mortar, which works as a bonding agent. Sometimes concrete blocks can be laid without mortar, which is called the dry-stack method. After laying blocks using the dry method, the center is filled with other materials, such as sand or gravel, to give the structure more stability.