Concrete

A.2.1: What is concrete?

Concrete is a combination of cement (most commonly known as Portland cement), fly ash, slag cement, including gravel, limestone, and/or granite. Cement is a material that is made up of a filler and a binder (cement paste). The mixture of these compounds usually involves two separate components; limestone and burning clay together. It is used everywhere from roads, houses, buildings, and recreational center.

Inside the sea defense wall, La Palma, CA.
Source: Michael Stewart, Lakin-Farm[1]

A.2.2: Brief History:

Concrete, or a form of the substance has been in use since the development of the Egyptian empire. They would combine lime (limestone, chalk, and oyster shells) and gypsum as binder to form a hard material similar to concrete. This method was used until the 1800s when inventor Joseph Aspdin burns the ground, using limestone and clay. By adding water and calcium oxide, he was able to produce a mixture called Portland cement, a dominate ingredient used in today’s manufacturing production.

A.2.3: How is it made?

Concrete is made through a heat and hydration process that can typically be manufactured on the construction it. It requires two important ingredients, Portland cement and water. Cement is a combination of limestone and clay, quarried from local sources. The clay and limestone go through  a crushing machine to turn the particles into a homogenous powder.  The powder the goes through a thin cylinder machine called a kiln, burning the mixture to achieve a chemical reaction. During this process, water remaining in the mixture will have been evaporated. Next, decomposition occurs in calcinations; causing water and carbon dioxide to be released from the material.  As calcinations is achieve, the cement will travel through the clinkering stage where the calcium silicates are formed due to the mixture of the powder and a small amount of gypsum. The last and final stage is the cooling process, where the Portland cement is brought of a cooler temperature at a regulated rate.

A.4.6: Components of Concrete

     A. Internal Structure

• The internal structure of glass is a composition of several properties. While most glass produce prior to the industrial revolution contained silica (SiO2), present-day glass contains multiple ingredients for multiple purposes. These elements range from but are not limited to sodium carbonate (Na2CO3), soda-lime, lead, boron, barium, thorium oxide, lanthanum oxide, iron, and cerium (IV) oxide. Other ingredients can be found in glass as a standard rule for production such as; calamite, “cullet” (recycled glass), sodium sulfate, sodium chloride, and/or antimony oxide. The image below demonstrates the internal structure of glass.

Internal structure of concrete.
Source: Petrography of Cementitious Materials

Internal structure of fly ash concrete.
Source: Petrography of Cementitious Materials


  B. Atomic and Molecular Structure




  C. Bonding Force

• Concrete is similar to ceramic material mainly because the raw material is brittle, hard, strong in compression, and  it can withstand weathering and high temperature; therefore it is classified under a polycrystalline solid. The composition of concrete holds an atomic structure where chemical compounds are compressed with a long-range order on a molecular scale. However, adding an additive or mixture to the component can adversely change the chemical make-up of concrete. For example, concrete must have a little water, but by adding too much will make the material brittle and fail under tension.
  

[1] http://www.lakin-farm.co.uk/wp-admin/images/gallery/concrete-structure.jpg




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