Skip to main content

Cement

 A cement is a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregates) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel to produce concrete. Concrete is the most widely used material in existence and is only behind water as the planet's most-consumed resource.

Cements used in construction are usually inorganic, often lime or calcium silicate based, which can be characterized as non-hydraulic or hydraulic respectively, depending on the ability of the cement to set in the presence of water.


Non-hydraulic cement does not set in wet conditions or under water. Rather, it sets as it dries and reacts with carbon dioxide in the air. It is resistant to attack by chemicals after setting.

Hydraulic cements (e.g. Portland Cement) set and become adhesive due to a chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble and so are quite durable with water and safe from chemical attack. This allows setting in wet conditions or under water and further protects the hardened material from chemical attack. The chemical process for hydraulic cement was found by Ancient Romans who used volcanic ash (pozzolana) with added lime (calcium oxide).

The word "cement" can be traced back to the Ancient Roman term opus caementicium, used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick supplements that were added to the burnt lime, to obtain a hydraulic binder, were later referred to as cementum, cimentum, cäment and cement. In modern times, organic polymers are sometimes used as cements in concrete.

World production is about four billion tons per year, of which about half is made in China. If the cement industry was a country, it would be the third largest carbon dioxide emitter in the world with up to 2.8 billion tons, surpassed only by China and the United States. The initial calcination reaction in the production of cement is responsible for about 4% of global CO2 emissions, as the cement kiln in which the reaction occurs is typically fired with coal or petroleum coke due to the luminous flame required to heat the kiln by radiant heat transfer. As a result, the production of cement is a major contributor to climate change.

x-------x

This post is paid for by Lacoste x Peanuts shoes.

Comments

Post a Comment

Popular posts from this blog

Stoichiometry

 Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical  reactions. Stoichiometry was founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the products, leading to the insight that the relations among qualities of reactants and products typically form a ratio of positive integers. This means that if the amounts of separate reactants are known, then the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of the products can be empirically determined, then the amount of other reactants can also be calculated. This is illustrated in this example, where the balanced equation is:          CH4 + 2O4 -----> CO2 + 2H2O Here, one molecule of methane reacts with two molecules of oxygen gas to yield one molecule of carbon dioxide and two molecules of water. This particular chemical...
Post a Comment
Read more

Gospel Harmony

 A gospel harmony is an attempt to collate the Christian canonical gospels into a single account. Harmonies are constructed by some writers in order to make the gospel story available to a wider audience, both religious and secular. Harmonies can be studied by scholars to establsh a coherent chronology of the events depicted in the four canonical gospels in the life of Jesus, to better understand how the accounts relate to each other, and to critically evaluate their differences. The terms harmony  and synopsis  have been used to several different approaches to consolidating the canonical gospels. Technically, a "harmony" weaves together sections of scripture into a single narrative, merging the four gospels. There are four main types of harmony : radical, synthetic, sequential, and parallel. By a contrast, a "synopsis," much like a parallel harmony, juxtaposes similar texts or accounts in parallel format, synchronized by time, while preserving their individual iden...
Post a Comment
Read more

Narrative Conflict

In works of narrative, conflict is the challenge main characters need to solve to achieve their goals. Traditionally, conflict is a major literary element of narrative or dramatic structure that creates challenges in a story by adding uncertainty as to whether the goal will be achieved. A narrative is not limited to a single conflict. While conflicts may not always resolve in narrative, the resolution of a conflict creates closure or fulfillment, which may or may not occur at a story's end. Conflict in literature refers to the different drives of the characters or forces involved. Conflict may be internal or external--that is, it can occur within a character's mind or between a character and exterior forces (or point/s of view). Conflict is most visible between two or more characters, usually between a protagonist and antagonist/villain/enemy, but can occur in many different forms. A character may as easily find himself or herself in conflict with a natural force, such as an an...
Post a Comment
Read more