Portland Cement

• A Portland Cement Primer

- John Bridge

Construction cement, the “glue” of the tile industry and others, was originally developed by the Romans, who thus revolutionized the masonry process, the ancient system of piling bricks or blocks upon one another and either notching them together or using mud or clay to keep things in place. No longer were gravity and friction the sole guiding principles of the art, for the new material made it possible to cause one masonry unit to actually stick to the next. Standing examples of the Romans’ masonry prowess can still be seen in Europe and portions of Asia. Natural cement was a breakthrough indeed.

Cement is made by combining limestone, clay, and other elements and “cooking” them in an oven or “kiln.” The resultant “clinkers” are then pulverized into a very fine powder. When water is introduced, the particles tend to recombine and bond to one another, forming a mass nearly as hard as the original stone from which the material is produced.

The curing (hardening) process is called hydration, and it occurs under water as readily as it does in open air. In fact, cement actually cures to a harder state when air is excluded from the process.

The big problem the Romans (and subsequent builders) faced was locating natural formations in which the necessary elements were present in more or less the correct proportions. Producing natural cement was (and is) a hit and miss proposition.

The product was not improved upon until the turn of the Twentieth Century, with the invention of “portland cement.” Advances in transportation made it feasible to accumulate the necessary elements in a central location and thus control the manufacturing process to a high degree. The newer material resembled the older, but the recipe could now be controlled from batch to batch. Consistency was at last obtainable.

Portland cement derives its name from the town of Portland, England, the color of whose world-famous building stone the product resembles. “Portland,” however, is now a universal trade term, and portland cement is produced throughout the world. Most of the products used in tile setting are based on portland cement.

Find out more about portland cement from the Portland Cement Association.

For advice in using portland cement products, and project help in general, visit us at the John Bridge Tile Forums.

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