Portland cement, definition

Cement is a powder, which mixed with water forms plastic mass, easy to shape (paste), setting with time and hardening gradually with strength increase. In marty standards the more exact Portland cement definitions were introduced. It is necessary because the name of cement is given to other binding materials, for example to anhydrite or magnesium oxychloride (the last is called Sorel cement). 

As described in previous sections, the standard method for treating durability in EN 206 and Eurocode 2 is based on the definition of the exposure class and determining for each class, the maximum w/c ratio, the minimum cement content and the minimum thickness of the concrete cover. EN 206 provides recommended (informative, that is non-normative) values for concrete composition in terms of maximum w/c ratio, minimum strength class and minimum cement content, assuming an intended working life of 50 y, the use of Portland cement (CEM I) and maximum aggregate size between 20 and 32 mm. In national documents these values and additional requirements can be further specified as normative values, as has been done for example in NEN 8005 (nl) for The Netherlands [12]. 

Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with its environment. Deterioration by physical causes is not called corrosion, but is described as erosion, galling, or wear. In some instances, chemical attack accompanies physical deterioration, as described by the following terms corrosion-erosion, corrosive wear, or fretting corrosion. Nonmetals are not included in this definition of corrosion. Plastics may swell or crack, wood may split or decay, granite may erode, and Portland cement may leach away, but the term corrosion, in this book, is restricted to chemical attack of metals. 

White s Test. A method for the detection of free lime, for example in Portland cement or dolomite refractories. A few mg of the powdered sample is placed on a glass microscope-slide and wetted with a solution of 5g phenol dissolved in 5 ml nitrobenzene with the addition of two drops of water. Micro-examination (x 80) will reveal the formation of long birefringent needles if free CaO is present. (A. H. White, Industr. Engng. Chem. 1, 5, 1909.) Whiteware. A general term for all those varieties of pottery that usually have a white body, e.g. tableware, sanitary ware and wall tiles. See also ceramic WHITEWARE, which has an ASTM definition. 

Aging, within the context of surface chemical considerations, refers to a decrease in surface area with time. For hydrated portland cement, this definition can be extended to include changes in solid volume, apparent volume, porosity, and some chemical changes (excluding hydration) which occur over extended periods of time. 

Research in new SCMs and portland cement-SCM blends is increasing significantly and it is expected to further increase in the next decades, considering the global challenges that the cement industry faces for development of more sustainable concrete. The SCMs with the highest potential are all less-crystalline or amorphous phases and NMR spectroscopy will definitely play an important role in the exploration of these new SCMs and their reactivity in cementitious systems. 

Definition. Concrete is a mixture of cement (portland, natural, or special cement), fine aggregate (sand), coarse aggregate (gravel), and water. Concrete mixtures are defined by a volume ratio, i.e., 1 2 4 concrete contains 1 part of cement, 2 parts of sand, and 4 parts of gravel. Additive materials, such as lime and calcium chloride, are used to prevent freezing, improve workability, and accelerate the setting time. 

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