Manufacturing Process of Cement Blocks
A cement block is actually a concrete block, also referred to as a concrete masonry unit (CMU). Portland cement is one ingredient used to make a concrete block. The blocks are used to build structures. They are a very economical yet durable building material. The blocks are fire resistant as well as energy efficient.
Concrete blocks typically have hollows to allow for setting the blocks on reinforcing bars for a strong foundation, as well as to make the blocks lighter for handling. The design of cement blocks allows for setting the blocks in place and then filling the hollows with wet concrete. This produces a strong wall.
The pliability of concrete, combined with strength and endurance, has allowed for its use in skyscrapers, bridges, superhighways and dams. The molded concrete block is an important element in concrete construction.
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History
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The Pantheon The Romans created a mixture using crushed rocks, burnt lime and water. This made a strong building material. People who marvel at the Pantheon in Rome can thank "caementicium," as the Roman's called the mixture. The Pantheon has held up for 2,000 years, and the dome is made of un-reinforced caementicium.
In more recent history, cement was used in the 1800s during the boom of the industrial revolution. The product did not withstand time as well as the more ancient versions. A Ukrainian scientist, Victor Glukhovsky, learned that when alkaline activators were added to cement it became very hard and did not degrade. The term for this alkaline mixture is geopolymers. This discovery led to the creation of today's strong concrete products.
There is a theory that the geopolymers were used in the creation of the pyramids, according to heritage-key.com. Limestone is alkaline, and limestone quarry sites are nearby the Great Pyramid of Giza.
Ingredients
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The key to the process for creating concrete is the ingredients used and the proportion of the ingredients. For concrete to produce a strong finished product that is easily workable while wet, it requires a fairly exact combination of ingredients.
Concrete is optimally a combination of 6 percent air, 11 percent Portland cement, 41 percent gravel or crushed stone (coarse aggregate), 26 percent sand or soil (fine aggregate) and 16 percent water, according to cement.org.
Once the constituents are combined in the correct proportions, the concrete begins to harden and must be placed into the forms.
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Forming Concrete
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For large-scale production, the mixture is pumped into pre-made block forms. Portland cement creates a chemical reaction with the water in the concrete mixture. This is called hyrdration and allows for adherence to the aggregates. Once placed in the forms, the concrete is vibrated to remove air pockets and a honeycomb effect that can occur.
Concrete Blocks
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Specifically to form concrete blocks, the concrete mixture is poured into steel molds. The molds are vibrated and compacted. The molding process is very fast, lasting 6.5 seconds. The molds are then removed and the blocks allowed to cure. The curing lasts from 18 to 36 hours. A kiln is used to quickly dry the blocks. Temperatures in the kiln range from 150 to 185 degrees, depending on the weight of the block. Often steam is introduced to create optimal curing conditions. The blocks are then dried and are ready for use.
Considerations
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The overall process can be very complex for large manufacturers that use conveyor belts, hoppers and large mixing vats. However, the process to make concrete blocks can be performed in a garage or workshop.
Concrete blocks are usually produced near their distribution point, which reduces transportation costs and makes them eco-friendly as well.
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References
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- Photo Credit Image by Flickr.com, courtesy of Steve Snodgrass Image by Flickr.com, courtesy of Kevin
