Concrete Masonry Units (CMU) | Concrete Blocks
Concrete masonry units (CMUs), also known as concrete blocks, are rectangular blocks made of concrete. They are typically hollow, with webs or fins that provide strength and help to reduce weight. CMUs are used in a variety of construction projects, including walls, foundations, and columns. CMUs are available in a variety of sizes and shapes with the most common size being 8 inches by 8 inches by 16 inches.
CMUs are made by pouring concrete into a mold and then curing the concrete. The concrete is typically made with Portland cement, water, sand, and gravel. The webs or fins are created by pouring concrete into the mold and then removing the excess concrete before the concrete cures.
Concrete masonry units were first invented in England in the 1850s and were later introduced to the United States in the late 1800s. In 1900, Harmon Palmer patented the first commercially successful concrete block machine. This led to a surge in the popularity of CMUs in the United States. By the 1920s, CMUs were being used in a wide variety of buildings, and their popularity has only continued to grow in the years since. Today, CMUs are a common building material used worldwide.
The mortar in a CMU wall is typically 3/8" (9.5 mm) thick. This is the standard mortar joint thickness for CMU walls. The mortar joint thickness can vary depending on the type of mortar used and the desired strength of the wall.
The cavities of CMU blocks can be used to improve the energy efficiency, soundproofing, fire protection, and drainage of a building. They can also be used to run wires and pipes through the wall.
CMU walls are not inherently waterproof. They are made of concrete, which is a porous material that can absorb water. However, CMU walls can be made waterproof by applying a water-resistant coating or membrane to the surface of the wall. This coating or membrane will create a barrier that prevents water from penetrating the wall.