The most important hydraulic constituents are the calcium silicates, C2S and C3S. Upon mixing with water, the calcium silicates react with water molecules to form calcium silicate hydrate (3CaO 2SiO23H2O) and calcium hydroxide (Ca [OH] 2). These compounds are given the shorthand notations C-S-H (represented by the average formula C3S2H3) and CH, and the Hydration reaction can be crudely represented by the following reactions:

During the initial stage of hydration, the parent compounds dissolve, and the dissolution of their chemical bonds generates a significant

I. Ordinary No special requirements General construction (e.g. sidewalks)

Soft materials are broken down by vigorous stirring with water in wash mills, producing a fine slurry, which is passed through screens to remove oversize particles.

Although the formulas above treat C-S-H as a specific stoichiometry, with the formula C3S2H3, it does not at all form an ordered structure of uniform composition. C-S-H is actually an amorphous gel with a highly variable stoichiometry. The ratio of C to S, for example, can range from 1:1 to 2:1, depending on mix design and curing conditions.

The clinker and the required amount of gypsum are ground to a fine powder in horizontal mills similar to those used for grinding the raw materials. The material may pass straight through the mill (open-circuit grinding), or coarser material may be separated from the ground product and returned to the mill for further grinding (closed-circuit grinding). Sometimes a small amount of a grinding aid is added to the feed material. For air-entraining cements the addition of an air-entraining agent is similarly made.

All except soft materials are first crushed, often in two stages, and then ground, usually in a rotating, cylindrical ball, or tube mills containing a charge of steel grinding balls. This grinding is done wet or dry, depending on the process in use, but for dry grinding the raw materials first may need to be dried in cylindrical, rotary dryers.

III. High early strength Higher strength soon after pouring Cold weather constructions

II. Modified Moderate sulfate resistance, moderate heat hydration Draining systems, sea walls, floor slabs, foundations

Some common words found in the essay are:
Crushing Grinding, C-S-H CH, Manufacture Cement, CH Hydration, Portland Cement, C3A C4AF, Modified Moderate, C2S C3S, Heat Low, CH C-S-H, raw materials, portland cement, calcium silicates, grinding raw materials, grinding raw, crushing grinding, dormant period, heat hydration, wet process, low heat, fed kiln, dormant period cement, process raw materials, = c3s2h3 +, types portland cement,
Approximate Word count = 1587
Approximate Pages = 6 (250 words per page double spaced)