Concrete Vs. Cement

Cement is a commodity and is merely one ingredient in the chemically engineered mixed product that is concrete.

What is concrete?

Concrete is one of the most essential construction materials. It is economical, offers continuity and solidity, and bonds with other materials. The active ingredients in concrete are cement and water which when combined create a chemical reaction. Cement includes the inactive ingredients, gravel and sand for cement strength.

Characteristics:

Strength of Concrete
The compressive strength of concrete is very high, but its tensile strength is relatively low. Since concrete must resist a great deal of stretching, bending, or twisting, it must be reinforced with steel.

Durability of Concrete
The durability of concrete, or its strength, is determined largely by the water-cement ratio. This durability gives concrete the ability to resist deterioration caused by ‘wear and tear’ and exposure to the elements. The character, size, and grading of the aggregate also have important effects on both strength and durability.

However, the character, size, and grading of the aggregate also have important effects on both strength and durability.

Water tightness of Concrete
In order to keep the concrete as watertight as possible, the amount of water used must be minimized to achieve the necessary degree of workability.

Concrete is also strong and fireproof.

Concrete that is subject to wear, such as floor slabs and pavements, must be capable of resisting abrasion.

Concrete has a wide variety of applications:
All important building elements, foundations, columns, walls, slabs, and roofs are made from concrete. Concrete is also used in the construction of roads, runways, bridges and dams.

What is cement?

Most cement used today is Portland cement. This is a combination of lime, silica, iron oxide, and alumina. It is usually manufactured from limestone mixed with shale, clay, or marl.

The major use of cement is for the production of concrete, which is one of the best hard-wearing construction materials available. TThe other important application of cement is for the production of mortar, which is used primarily for joining bricks, blocks, or stones in walls. Cement can also be used independently as a grouting material. In modern technology, cement is also used in the process of solidification/stabilization that is a technique used for the removal of contaminated wastes. Another significant use of cement is in the engineered soils by which the poor quality soils are improved by the addition of cement, after which the soils are usable as a base for foundations for different constructions.

The production of cement causes a number of harmful effects to the environment, including significant carbon dioxide emissions. Additional pollution is generated by the release of dust and gases from the operation of machinery and blasting conducted in the quarries. Appropriate equipment is used to minimize the dust emissions and to separate gases in order to reduce the harmful effects on the environment.

China ACM Company Information
  • Cement is a commodity
  • Concrete is a value added product

Chad Syverson, Associate Professor of Economics, University of Chicago states, "A good place to start is to clear up some confusion that I constantly encounter. First, cement and concrete are not the same thing, even though the two terms are often used interchangeably in conversation. Concrete comprises the roads we drive on and the buildings in which we live and work. Cement is an ingredient in concrete; it is mixed with sand, gravel, water, and small amounts of chemical admixtures to make concrete. Cement holds the key reagent that allows concrete to harden (through a chemical reaction called "hydration") into a useful structural material, but it is worthless for such purposes if used by itself. Referring to concrete as "cement" is a bit like referring to bread as "flour."

A second confusion is that the ready-mixed (alternatively: ready-mix) concrete industry is the same as the industry of precast or prefabricated concrete products. Ready-mixed concrete is the fluid form of concrete delivered to construction sites in the familiar barrel-backed mixer trucks (not "cement" trucks!) and poured into a desired shape. Precast or prefabricated concrete products, like block, brick, pipe, and reinforced structural members, are instead made by pouring concrete into molds and curing them on the factory site. In the government industrial classification systems, ready-mix concrete is SIC 3273 or NAICS 32732, while precast or prefabricated concrete products are classified separately, as SICs 3271 and 3272 or NAICS 32733 and 32739."

Chad Syverson
Chad Syverson is Associate Professor of Economics, University of Chicago, Chicago, Illinois, and Faculty Research Fellow, National Bureau of Economic Research, Cambridge, Massachusetts.
http://home.uchicago.edu/~syverson/marketsrmc.pdf