Concrete Block

Concrete Block

A concrete block is a kind of precast concrete product used in construction.  It is primarily used in the construction of walls and it is sometimes called a concrete masonry unit (CMU).  The design of a concrete block can vary from having one or more hollow cavities with it sides case smooth or with a design.  It is stacked one at a time and held together with fresh concrete mortar to for the length and height of the wall that we need. 

History of concrete block

The first hollow concrete block was designed in 1890 by Harmon S. Palmer in the United States.  After 10 years of experimenting, Palmer patented the design in 1900.  Palmer’s blocks were 8 inch (20.3 cm) by 10 inch (25.4 cm) by 30 inch (76.2 cm) and they were so heavy they had to be lifted into place with a small crane.  By 1905, an estimated 1500 companies were manufacturing concrete blocks in the US.  These early blocks were usually cast by hand, and the average output was about 10 blocks per person per hour.  Today, concrete block manufacturing is a highly automated process that can produce up to 2000 blocks per hour.  (www.madehow.com)  In recent years, with the emphasis on green products, lightweight green concrete blocks are produced.  This kind of blocks has foam inside it to replace some of the concrete, making it lighter. 

Raw material

Just like common concrete mixtures used for general construction purposes, concrete blocks also consist of portland cement, water, sand and gravel.  When comparing the two, the concrete mixture used for blocks has a higher percentage of sand and a lower percentage of gravel and water.  Therefore, this produces a very dry, stiff mixture that holds its shape when it is removed from the block mold. 

Lightweight concrete blocks are made by replacing the sand and gravel with expanded clay, shade or slate.  These three kinds of materials are produced by crushing the raw materials and heating them to about 1093°C.  At this temperature, the material puffs up because of the rapid generation of gases caused by the combustion of small quantities of organic material trapped inside.  Lightweight concrete blocks are commonly used to build non-load-bearing walls and partitions.  Other materials that can be used to produce lightweight concrete block for example expanded blast furnace slag and natural volcanic materials such as pumice and scoria. 

Future of concrete block

With the use of concrete blocks, construction of a building will be faster and less expensive.  The structures are also more durable and energy efficient.  Furthermore, with the continuous development through architects and block manufacturers, new shapes and sizes will be developed.