The Concrete Block Making Process

Concrete blocks are strong, inexpensive building materials.

Concrete blocks are a widely used product in construction. They are made in factories by the thousands and sent out to be used in everything from houses to military bunkers. Many people take these blocks for granted without considering where they came from. The process to make concrete blocks involves several steps, including measuring and mixing of raw materials, molding the concrete and curing the finished blocks. Does this Spark an idea?

History and Styles

The first concrete blocks, as they are known today, were invented at the end of the 19th century by Harmon S. Palmer. His blocks were made by hand at a rate of about 10 per hour as opposed to modern automated manufacturing which can produce blocks at a rate of 2000 per hour. Modern concrete blocks come in a variety of specialized styles. Cinder blocks have higher soundproofing and thermal qualities than standard blocks while lightweight blocks are designed to reduce the average 40-lb. weight of most concrete blocks.

Block Materials

Concrete blocks are typically made of portland cement, sand, gravel and water. The concrete mixture for blocks tends to contain more sand and less gravel and water than concrete made for other purposes, which results in a smooth, dry product that holds its shape well once it is demolded. Specialized blocks contain different materials. For example, cinder blocks replace sand and gravel with granulated coal or volcanic cinders. Lightweight blocks may use expanded clay, shale or slate in place of sand and gravel. Various pigments and glazes may also be added to make the blocks more decorative.

Mixing and Molding

The dry materials are mixed in specific proportions in large, industrial mixers. Once the dry materials are combined, a small amount of water is added and the concrete is poured into molds. Each mold consists of an outer box in the shape of a block with two plugs to keep the inner area of the block hollow. These molds are often vibrated while being filled to prevent air pockets from being trapped. Once the molds are full, the concrete is compacted from above to condense the concrete into blocks.

Curing

Once the blocks are condensed, they are pushed out of the molds. The low water content in the concrete allows the blocks to hold their shape, but they can still be damaged if not treated carefully. The demolded blocks are then left to cure for up to 14 days or baked in a kiln for several hours to cure them more rapidly. Once the blocks have cured, they are ready to be sent to a construction site.

References

• MadeHow: How Concrete Block Is Made
• DA Sustainable Livelihoods: Concrete Block Technology

Resources

• Read this Article in UK English