Cement

What is cement?

Cement is a fine, soft powder used as a binder because it hardens after contact with water. It is produced from a mixture of limestone and clay that’s charred and then ground up.

How is cement made?

Since ancient Greece and Rome, humankind has used cement for construction. However, the process for making this quick-drying gray paste has changed significantly since those times. The rudimentary methods of yesteryear are no longer used to work with limestone; instead, special machinery is used to generate very fine powders in quantities never before seen. 

Starting in the 19th century, the industrialization of cement production has allowed this material to become present in a wide variety of construction sites, and it has also been used for aesthetic and utilitarian purposes in modern architecture.

How is construction cement made? 

• The process begins in the quarry with the extraction of limestone and clay.
• The raw material is transported to a special plant, where it’s crushed.

• In pre-homogenization, gamma-ray equipment analyzes the raw material, and it is then mixed with precise amounts of iron and limestone, which is determined according to the type of cement being made.
• This rustic mixture is pulverized during grinding until a fine “flour” is obtained.
• Then, it goes to the homogenization silo.
• When subjected to high temperatures, it crystallizes and then cools, transforming into a homogenized ground substance (small, gray round crystallized stones).
• Pre-grinding. After a certain amount of time in storage, the clinker passes through a roller mill.
• During grinding, the clinker is ground with gypsum (the gypsum-to-clinker ratio will determine the type of cement produced).
• Finally, the finished cement is packed and distributed in bags. 

What types of cement are there?

1. Ordinary Portland Cement (OPC): this is produced and used around the world. It’s widely used for various purposes, including concrete, mortar (masonry), plaster, grout, and wall putty.
2. Portland Pozzolana Cement (PPC): (OPC + pozzolanic clinker) ideal for marine structures, sewage works, foundation works, docks, bridges, etc.
3. Cement with high alumina content (HAC): (OPC + bauxite and limestone) ideal for structures subjected to high temperatures or that generate a lot of heat, such as foundries, workshops, and refractories.
4. Blast furnace slag cement (clinker + 60% slag): ideal for structures on tight budgets.
5. Sulfate resistant cement: used with soils or groundwater that have more than 0.2% or 0.3% g/L of calcium sulfate salts, respectively.
6. Fast-setting cement: for underwater structures and those in cold, rainy weather conditions.

Which countries produce cement?

The main cement producers today are:

1. China: more than two thousand four hundred (2,400) tons of cement per year
2. India: more than two hundred (200) tons of cement per year
3. United States, Russia, Turkey, and Japan: less than 100 tons/year

What are the benefits of building with cement?

Cement is an essential building material; in fact, it is the one most widely used in the world. Most structures use it in at least one of their stages: foundations, floors, lintels, interior or exterior walls, or ceilings.

The main benefit of cement is that it is a resistant, durable material that’s low-cost and has a wide variety of applications. This makes it a favorite among architects and construction companies around the world.

There are many advantages or benefits to building with cement: 

• It makes financial sense.
• It’s strong and durable: it has a tested durability of thousands of years. In fact, the longer the building stands, the more resistant it becomes. It’s not affected by humidity, and it can withstand major weather changes.
• It requires very little maintenance. 
• It is versatile. It can be used in building construction or paving, for bridges spanning the sea, or to make park benches. 
• It’s not affected by fire. This makes it a suitable construction material for important buildings like hospitals, schools, museums, libraries, and banks. 
• Sustainability. It is a natural insulator, which is why it is less dependent on heating and air conditioning systems, thus achieving more efficient structures. 

How will cement be made in the future?

Every day, new mixtures and applications for cement are discovered. The latest technological innovations allow cement to be made faster, of higher quality, and at lower cost, ensuring that it will remain an essential building material for years to come. 

Technology has also brought new uses (expanding cement), applications (decorative micro-cement), and cement-based construction methods (such as 3D printing). 

Recently, Henk Jonkers, a Dutch professor of microbiology, managed to create a bio-concrete that repairs itself when cracked. By mixing the cement with specific bacteria that produce limestone, he has created an ultra-strong “living” material that will be able to protect internal steel reinforcements from water damage.

These technological advances lead us to predict that cement will continue to be one of the most important construction materials and that it will continue to shape the skylines of our future cities over the next century.